TERRESTRIAL AND FRESHWATER OF EARLY

ELIZABETH T. SMITH Research Associate The Australian Museum, Sydney

A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy

February 2009

Vertebrate Palaeontology Laboratory School of Biological, Earth and Environmental Sciences University of , Sydney

ABSTRACT

An unusual fauna from Lightning Ridge, New South Wales () reveals that Australian turtles had a more extensive Mesozoic history than previously indicated. Reevaluation of several primitive groups provides novel information on turtle in the southern hemisphere.

Seven turtle taxa are identified at Lightning Ridge. Two are Testudines indet. and two indeterminate chelid groups are evinced by isolated elements. Three new taxa are assigned to the new Spoochelyidae in the superfamily Meiolanoidea.

Spoochelys ormondea n. fam., gen. et sp., Sunflashemys bartondracketti n. gen. et sp. and Opalania baagiwayamba n. gen. et sp. are predominantly land-living turtles with high-domed shells and short manus and pes. The sister-group relationship with the , supported by a suite of cranial and postcranial synapomorphies, increases the stratigraphic range of the horned turtles by around ~ 50 my. Primitive structures in Spoochelys (postparietal, supratemporal and interpterygoid vacuity), occur with derived features that are variably developed across and turtles.

Phylogenetic analysis precariously resolves the meiolanoids as sister group to a clade containing Palaeochersis and Proterochersis. Limited pleurodiran attributes suggest that meiolanoids may be pleurodiromorphs, closer to primitive pleurodires than to cryptodires. As basal ‘side-necked’ turtles, the Lightning Ridge meiolanoids permit first insights into cranial and postcranial progressions in pleurodiran stem taxa. Evidence of diverse meiolanoids in Australia and ancient radiations of meiolanoid-like turtles in southern Pangea, suggest that the horned turtles are a Triassic group and that the dichotomy between and occurred well before the .

Early Cretaceous chelids at Lightning Ridge occur at higher palaeolatitude than in . The temporal range of Australian chelids is extended by ~ 50 my, demonstrating that chelids had a Jurassic history in Australia, with broad diversifications across the polar supercontinent.

The palaeoecological setting of Lightning Ridge is comprehensively described for the first time. Diverse invertebrates and vertebrates include terrestrial, freshwater aquatic and rare marine forms that are anomalous at this near-polar palaeolatitude (~65-70oS). The anachronistic occurrence in Early Cretaceous Australia of distinctive radiations of ‘Triassic-type’ turtles, and other relic groups, implies prolonged intervals of biogeographic isolation in the eastern provinces of Pangea.

Keywords: Early Cretaceous Australia; Lightning Ridge; Meiolanoidea; . ACKNOWLEDGEMENTS

My sincere appreciation and thanks to my supervisors Dr Michael Archer and Dr Suzanne Hand, University of New South Wales, for expertise, wisdom and encouragement when it was most needed; Henk Godthelp for his enthusiasm for search and research at Lightning Ridge and for the braincase of cf. Warkalania from Riversleigh; Robin Beck for perseverance and utmost patience (PAUP); Karen Black and Anna Sainsbury for molding and casting the Spook and braincase; Dr Thomas Rich, National Museum of ; Lesley and Gerry Kool and Dr Patricia Vickers-Rich, Monash Science Centre, Melbourne; Dr Alex Ritchie and Robert Jones of the Australian Museum, Sydney; Dr Ralph Molnar and Joanne Wilkinson of the Museum, Brisbane; Dr Ben Kear; Dr Susan Turner; Dr Jeffrey Stilwell, James Bresnahan, Rodney Berrell - all helped in various capacities, and deserve my gratitude. Dr Gene Gaffney offered advice, goodwill, reprints and instruction, sent photographs of the Niolamia type skull and provided access to type material of Chubutemys. Dr P M Datta, Subhash Sen and Asish Kumar Ray at the Geological Survey of India, Kolkata, permitted me to examine, sketch and photograph the type material of Indochelys spatulata at short notice, and graciously. Thanks are due to Walgett Shire Council for supporting the Australian Opal Centre project; and to the Lightning Ridge Bowling Club for helping with acquisitions.

I am indebted – the science of palaeontology is indebted - to the opal miners of Lightning Ridge. Palaeontology at Lightning Ridge is a community enterprise, relying heavily on the energetic and generous involvement of the opal miners. Over the past twenty five years, hundreds of opalised have been made available to the Australian Museum, Sydney, and the Australian Opal Centre, Lightning Ridge. Thankyou to Peter and Brett Barton who donated the Sunflash Turtle to the Australian Museum under the Federal Government’s Cultural Gifts Program. Peter and Brett met the Sunflash Turtle underground on the Coocoran and allowed me to collect further material. Dave Roussel, Rod Abels and my daughter Clytie helped to rescue the turtle from the Tyrone’s site. Warmest thanks to many other CGP donors - Bob Sutherland, Neroli and Stephen Bevan, Imo and Louise Stein, Rob and Debbie Brogan, Ken and Marie Lindquist, Dave Roussel and Lalja Petersson, John Cucuk, Stephen Turner, George and Bill Molder, Graeme and Christine Thomson, Clytie Smith, Peter and Vicki Drackett, Joe Walker, Paul Burza, Brian Senior, Dave Sanders, Stewart-Tranter Brown, David and Greg Lane, Colin and Marie Fletcher, Marcel and Sam Miltenburg, Adrian Boot, Dave Barclay, Matthew Goodwin, Mick and Doris Cooke, Jack Fahey and Emilia Katajisto. Praise to the valiant - Ormie Molyneux who loaned the Spook skull and braincase for study over many years, with commendable fortitude and good humour; Ed Long and Henny Kunzelman, Nils and Bea Tape, Bob Cropp, Dave and Alan Galman, Chris Underwood, Ken Hudson, Les Price, Fred Mallouk, Ian Cops, Peter Hall, Dusan, Brownie, Andrew Lindsay, Jo Babic, Virgil, Peter and Lisa Carroll, Andrew Cody, Barefoot Mick Dundee, New Blue from Kellies Two, Doug and Loppy, Martin, Crain Johannson, Slim, Michelle and Gussy Knee, Eric the Viking, Greg Bateup, Hydro Tony, Richard Wagner, James Haverhoek, Peter McKenzie, Geoff Peady, Stan the Man, Greg Johnston, Arthur and Joe Molyneux, Larry White, Richard Slip, Max Caslick, Orange Joe, Silly Pinkies, Smith Boys, Chris Gawthorpe, Graeme Lester, Brian Casement, Fraser Island George, Rod McCracken, Joe Belicka, Laurie Kree, John McCabe, Ken Stephenson, Darren Mack, Bill Kotru, Bob Barrett, Drago Panich, Franz Roehleder, Lennie Cram, Butch McFadden, The Warlords, Darryl Ferguson, Norm, Stardust Clive, Alf White, Col Duff, Vic Morgan, Toby and Matthew Egan, Sali Money, Alan Summers, Mick and Donna Lund, Michael and Rebel Matson, Marilyn Milas, Anne-Marie Deane, Kerry Reid, Murray Gatt, Lizard, June Barker and Rose Fernando. Thankyou one and all.

Margie and Warwick Schofield, Tony and Karola, Shovel, Graeme Anderson, Barbara Moritz, Bev Ogle, Roland Beckett, Gwen Jenkins, and the little Scotties and cohorts from next door, contributed in many special ways. Jenni Brammall helped with powerpoints, photographs, layout of figures for chapters four, five and seven, general support and commitment. Thanks also to Tiggen, my Mum and Dad, Rohan, Brinny, David and Penny, for keeping this slow old turtle on track. My husband Robert photographed, photoshopped and held the fort. Gurukangaroo doesn’t believe in turtles but he sacrificed at least two trips to India for this. My eternal gratitude. TABLE OF CONTENTS

Page ABSTRACT Acknowledgements Table of contents Abbreviations

CHAPTER ONE 1 INTRODUCTION

CHAPTER TWO 13 Spoochelys ormondea n. fam., gen. et sp. (Meiolanoidea: Spoochelyidae), an archaic meiolaniid-like land turtle from Lightning Ridge, New South Wales, Australia

CHAPTER THREE 55 Sunflashemys bartondrackettii n. gen. et sp. (Meiolanoidea: Spoochelyidae), a primitive swamp turtle from the opal fields of Lightning Ridge, New South Wales, Australia

CHAPTER FOUR 90 Opalania baagiiwayamba n. gen. et sp. (Meiolanoidea: Spoochelyidae), a near-polar land turtle from the Early Cretaceous of Lightning Ridge, New South Wales, Australia

CHAPTER FIVE 106 New cranial material of a meiolaniid cf. Warkalania from the of Riversleigh, North Queensland

CHAPTER SIX 116 Redescription and reinterpretation of the Liassic turtle Indochelys spatulata Datta et al. 2000 from Maharashtra, India

CHAPTER SEVEN 129 Redescription of the Casterton steinkern, Chelycarapookus arcuatus Warren 1969, from the Albian of western Victoria

CHAPTER EIGHT 141 Australia’s oldest chelid pleurodires from Lightning Ridge, New South Wales - first evidence of chelids from Mesozoic near-polar Australia

CHAPTER NINE 151 Phylogenetic analysis - non-marine turtles of Early Cretaceous Australia, and relationships of the superfamily Meiolanoidea

CHAPTER TEN 216 The Lightning Ridge fossil flora and fauna – a diverse high- latitude, warm climate biota from Early Cretaceous Australia

CHAPTER ELEVEN 294 Palaeoecology of terrestrial and freshwater turtles of Lightning Ridge, New South Wales

CHAPTER TWELVE 301 Biogeography of non-marine turtles of Early Cretaceous Australia

CHAPTER THIRTEEN 308 Possible Triassic origin for the horned turtles (Testudines: Meiolanoidea) and implications for turtle relationships CHAPTER FOURTEEN 312 CONCLUSIONS

REFERENCES 318

APPENDICES 1.0 Phylogenetic analysis – PAUP documentation 352 2.0 Lightning Ridge fossil flora and fauna survey 374 3.0 The Lightning Ridge local fauna 386

LIST OF FIGURES Early Cretaceous turtle sites of Australia. 12

Spoochelys ormondea n. fam., gen. et sp. from the Albian of 40 - 54 Lightning Ridge, New South Wales, Australia.

Sunflashemys bartondracketti n. gen. et sp. from the Albian of 82-89 Lightning Ridge, New South Wales, Australia.

Opalania baagiwayamba n. gen. et sp. from the Albian of Lightning 102-105 Ridge, New South Wales, Australia.

A meiolaniid cf. Warkalania carinaminor Gaffney et al. 1992, from 115 the Miocene of Riversleigh, Queensland.

Indochelys spatulata Datta et al. 2001 from the Liassic 125-128 of Maharashtra, India.

Chelycarapookus arcuatus Warren 1969 from the Albian 138-140 of Casterton, Victoria

Isolated elements of indeterminate chelids (Chelidae indet.) 149-150 from the Albian of Lightning Ridge, New South Wales, Australia. Comparison of skull skute patterns and cranial bones 213 in , Spoochelys and meiolaniids.

Chubutemys copelloi Gaffney et al. 2007 from the of Chubut, 214 Argentina.

Meiolania platyceps from the of . 215 Articulated cervical series.

The Lightning Ridge fossil fauna. 266-293

Mesozoic distribution of primitive non-marine turtles. 307 ABBREVIATIONS Institutional AM Australian Museum, Sydney AMNH American Museum of Natural History, New York GSI Geological Survey of India, Kolkata LRF Australian Opal Centre, Lightning Ridge NMVP National Museum of Victoria, Melbourne QM Queensland Museum, Brisbane

Anatomical Cranial ang angular art articular ast aditus canalis stapedio -temporalis btp basipterygoid process bo basioccipital bs basisphenoid bsc basisphenoid crista ca columella auris caj cavum acustico jugulare cc canalis cavernosus cci canalis caroticus internus ccl canalis caroticus lateralis cav lab cavum labyrinthicum cor coronoid den dentary ds dorsum sellae epi epipterygoid ex exoccipital fcb foramen caroticum basisphenoidale fic foramen intermandibularis caudalis fim foramen intermandibularis medius fo fenestra ovalis fmk fossa meckelii fnf foramen nervi facialis fpct foramen posterius chorda tympani fpcci foramen posterius canalis carotici interni fpccl foramen posterius canalis carotici laterale fr frontal ica incisura columellae auris ivac interpterygoid vacuity ju jugal mx maxilla op opisthotic pa parietal pf prefrontal pio processus interfenestralis of opisthotic po postorbital pp postparietal pr prootic pra prearticular pt pterygoid qj quadratojugal qu quadrate rb rostrum basisphenoidale rst recessus scalae tympani scm sulcus cartilaginis meckelii so supraoccipital sp splenial sq squamosal st supratemporal sur surangular tab tabular VII foramen nervi facialis vo vomer XII foramen nervi hypoglossi Postcranial ax axillary buttress c costal ent entoplastron ing inguinal buttress n neural nu nuchal pl pleural hyo hyoplastron hypo hypoplastron mes mesoplastron sms supramarginal su suprapygal v vertebral x xiphiplastron CHAPTER ONE

INTRODUCTION

Turtles are a common component of vertebrate sites worldwide, prodigiously abundant in places. The great turtle cemeteries of Mongolia comprise literally hundreds of shells or complete skeletons (Sukhanov 2000), and in Australia, Crusty Meat Pie Site at Riversleigh (Miocene, Queensland) boasts thousands of compacted individuals (Archer et al. 1991). Taken as a whole however, the Australian fossil turtle record is pathetically sparse, with comparatively few specimens representing only a handful of groups (Gaffney 1991).

The Mesozoic record is particularly scant. When turtles first appear in the Australian record, they had completed at least half of their evolutionary history. Australia’s oldest non-marine turtles are from deltaic and riverine deposits in the Early Cretaceous of Victoria, New South Wales and Queensland (Fig. 1). At this time, marine turtles are restricted to Queensland (Lydekker 1889; Longman 1915; Molnar 1980, 1991; Gaffney 1881, 1991; Kear 2003; Kear and Lee 2005). Non-marine turtles occur in the Aptian Wonthaggi (Gippsland Basin) and Albian Eumeralla (Otway Basin) and Merino formations of Victoria; the lower-middle Albian Griman Creek Formation () of Lightning Ridge, New South Wales; and the Late Albian- Winton Formation (), Queensland. Apart from type descriptions of the fluviatile turtles Chelycarapookus arcuatus Warren 1969 from Casterton and Otwayemys cunicularis Gaffney et al. 1998 from Cape Otway, both based on incomplete material, the non-marine turtles are very poorly documented, and published works are outdated, limited and generalised (Chapman 1919; Gaffney 1981, 1991; Molnar 1991).

This meagre Mesozoic tally is now substantially augmented by new records from Lightning Ridge, where turtle bones dominate the vertebrate assemblages in many places across the opal fields. Up to seven taxa demonstrate the presence in Australia of lineages far older and more diverse than previously recognized. Lightning Ridge is one of the richest fossil turtle localities in Australia. Primitive meiolaniid-like groups and

1 chelid pleurodires are present, and at least two undetermined turtle taxa are evinced by single specimens of unclear affinities. Given the complexity of coastal deltaic depositions, it is likely that additional turtle groups are represented in the Lightning Ridge assemblages.

In Chapters Two, Three and Four of this thesis, three new turtles are described and analysed. Spoochelys ormondea n. gen. et sp., Sunflashemys bartondrackettii n. gen. et sp. and Opalania baagiiwayamba n. gen. et sp., are assigned to the new family Spoochelyidae, sister-clade to Meiolaniidae in the superfamily Meiolanoidea. Meiolanoidea was erected but not diagnosed by Gaffney (1996).

As the oldest known members of a bizarre and controversial lineage, the Lightning Ridge taxa extend the temporal range of the horned turtles by around 50 my. The previous earliest record is from the - of Rio Negro, Patagonia (Sterli and de la Fuente, cited Joyce and Parham 2006). Spoochelys and Opalania are heavily-built terrestrial turtles; Sunflashemys is more gracile and possibly semi-aquatic. These three forms are anachronistically primitive, providing first insights into basal members of a fascinating and enigmatic group.

Australia’s oldest chelid pleurodires are represented at Lightning Ridge by a handful of isolated elements from several sites (Chapter Eight). Identified as Chelidae indet. (Hyperfamily Cheloides Gray 1825), this is the first pre- evidence for chelids outside South America. The Lightning Ridge chelids are around 50 my older than the previous oldest record for Australian chelids from Redbank Plains, Queensland (Lapparent de Broin and Molnar 2001). Although chelids are the most common turtles in Cainozoic Australian faunas, no fossil Australian chelids have been identified apart from those referrable to recent taxa (Gaffney 1991). In comparison to that of South America, the Australian chelid record is flimsy, and in fact the evolutionary history of the Chelidae is very poorly understood. Australian Tertiary chelids are distinctly different from South American forms. At present it is unclear whether the Lightning Ridge chelids represent taxa previously unknown in Australia, or taxa closely related to the South American groups.

2 Australian Mesozoic turtles are found in near-polar locations, ~ 60o-70oS. Although warm temperatures predominated during the Albian (Li et al. 2000; Henderson et al. 2000) and mild conditions are inferred, at these palaeolatitudes, palaeoclimates were strongly seasonal, with high summer rainfall or snowmelt and cool to cold winters with weeks or months of polar darkness. Non-marine turtles of Early Cretaceous Australia occur in diverse assemblages which include invertebrate and vertebrate groups that are typical of temperate and tropical regimes. Palaeobiological implications of the Victorian turtle locations have been thoroughly documented (Rich et al. 1988; Rich and Rich 1989; Vickers-Rich 1996; Rich 1996). Palaeoecology of the Queensland locations is less well known, partly because distributions are scattered.

Chapter Ten of this thesis presents the first monographic overview of the Lightning Ridge locality, placing the unique turtle fauna in palaeoecological and biogeographical context (Chapters Eleven and Twelve). Expanding on preliminary work by Smith and Smith (1999a), Chapter Ten is underpinned by a survey of fossil material from 40 sample locations widely dispersed across the opal fields. Lists of microsite assortments, maps and fossil taxa are given in Appendices 2.0 and 3.0. All specimens itemized in the microsite assemblages (Appendix 2.0.2) are held in public collections, however a number of specimens discussed and shown in figures in this thesis are still privately owned. These specimens are held at the Australian Opal Centre, Lightning Ridge, pending donation to that institution. It is anticipated that the donations will be made in mid-2009, under the Australian Federal Government’s Cultural Gifts Program.

At Lightning Ridge, turtle bones are found in continental floodplain deposits laid down on the margins of the epicontinental Eromanga Sea. Biofacies of Finch Claystone (‘opal dirt’) occur as discontinuous layers and lenses of fine-grained kaolinitic illite- rich mudstones and siltstones, interspersed sequentially throughout the Wallangulla Sandstone Member of the Griman Creek Formation. Smaller-scale dating and stratigraphic correlations have not been undertaken for units within the Griman Creek Formation in the vicinity of Lightning Ridge. Consequently much uncertainty exists in relation to taxonomic assignments of isolated elements from disparate sites, from the various opal-bearing ‘levels’. Separation of specimens into different taxa and morphotypes is fraught with difficulties, a painstaking process that is open to review. Further scientific excavation on-field, and investigations of stratigraphy,

3 sedimentology, palynology and micropalaeontology will help to resolve some of these issues. Considering that Lightning Ridge is the major Early Cretaceous fossil site in New South Wales and one of the richest known near-polar localities, such investigations are long overdue.

During this study, original or type material of a number of fossil turtles from Australia and overseas has been reexamined. Comparisons are made across a range of Mesozoic forms and key osteological features in several taxa are reinterpreted. Indochelys spatulata Datta et al. 2000 ( Liassic, India), the only pre-Cretaceous turtle record from eastern Pangea, and Chelycarapookus from Victoria are redescribed (Chapters Six and Seven). Chelycarapookus has not been subject previously to cladistic analysis. New material is documented of a meiolaniid cf. Warkalania carinaminor Gaffney et al. 1992 from the Miocene of Riversleigh, Queensland (Chapter Five). Chubutemys copelloi Gaffney et al. 2007 from the Aptian (Cerro Barcino Formation) of Patagonia, and platyceps Owen 1886 from the Pleistocene of Lord Howe Island are comprehensively reevaluated (Chapter Nine). Otwayemys which is essentially a shell , and NMVP199057, a partial carapace/plastron specimen from Kilcunda (Inverloch; Strzelecki Group, Victoria) are incorporated in the phylogenetic analysis. Chapter Nine provides detailed commentary on characters used in the cladistic analysis. Alternative reconstructions are given for Indochelys (Fig. 33), Chubutemys (Fig. 40) and Chelycarapookus (Fig. 36). PAUP analysis documentation, including character report, datamatrix and phylogenetic trees are presented in Appendix 1.0.

To date, the entire Australian fossil turtle record consists of only five groups: Meiolanoidea (as diagnosed herein), Chelidae, Chelonioidea, and Carettochelyidae (Gaffney 1981; Molnar 1991). By way of contrast, six families are present in the () of Alberta, Canada (Brinkman 2005). The assertion that Australia has a lower diversity of fossil turtles than any continent except Antarctica (Gaffney 1991) still holds.

Nonetheless, understanding of early turtle evolution in south-eastern Australia has progressed rapidly in the past decade with new publications and interesting discoveries from Early Cretaceous Australia. Cratochelone berneyi Longman 1915 and costata Lydekker 1889 from the latest mid- to late Albian (Toolebuc

4 Formation), Rolling Downs Group, have been reviewed recently (Kear 2003). The protostegid Bouliachelys suteri Kear and Lee 2005 from Winton (middle-late Albian) is notable for its primitive phylogenetic status. Remains of embryonic or juvenile protostegids from inside the thoracic region of an ichthyosaur from Hughenden (Early Cretaceous) provide first evidence of baby turtles predated by ichthyosaurs (Kear et al. 2003); and Kear (2006) reports on gut contents of protostegids from the (Cenomanian). New material from Queensland includes a skull (possibly a freshwater turtle) and other undescribed specimens from Winton (Molnar 1991; Kear 2003; Henk Godthelp pers. comm.). The newly-discovered Hazel Creek site (Toolebuc Formation) near Mt Isa has produced evidence of a juvenile of Notochelone (pers. obs.), the northernmost distribution for this taxon.

In recent years, the Victorian sites at Cape Otway and Inverloch have yielded a plethora of turtle elements including a near-complete skull, several partial and shell remains that are presently under study (Lesley Kool and Gene Gaffney pers. communs.). It is unclear at this stage which, if any, of this material is referrable to Otwayemys or Chelycarapookus, however cranial and carapace specimens indicate at least one undescribed taxon sharing features with the Lightning Ridge turtles (pers. obs.).

The accepted view that turtles have a relatively dense fossil record does not apply to Early Mesozoic occurrences, which are punctuated by immense spatial, structural and temporal discontinuities (Broin 1984; Jenkins et al. 1994; Gaffney and Kitching 1995; Hirayama et al. 2000; Sukhanov 2000, 2006; Datta et al. 2000; Gaffney et al. 2006; Sterli and Joyce 2007; Sterli 2008). Extant turtles belong to one of two groups – the Pleurodira or ‘side-necked’ turtles that retract the head laterally; and the Cryptodira, ‘hidden neck’ forms which conceal the head by vertical flexion. Hypothetical timing of the primary divergence (the ‘casichelydian’ dichotomy of Gaffney 1975, 1990, 1996; Gaffney et al. 1988; Gaffney and Meylan 1991) alternates between mid- to Late Triassic and mid- to , and structures common to the closest ancestor of the crown groups are unclear. Specimens are limited, and systematics and nomenclatures are unstable (Shaffer et al. 1997; Gaffney et al. 2006; Gaffney et al. 2007; Parham and Hutchison 2003; Joyce et al. 2004; Joyce 2007; Sterli et al. 2007; Danilov and Parham 2008).

5 Turtle phylogenetic theory is now in a state of flux. Debate revolves around use of geological range to distinguish extinct from living groups, in the terms ‘stem’ and ‘crown’, and relative merits of Linnaean versus Phylocode classification (Lee 1995; Joyce et al. 2004; Joyce 2007; Gaffney et al. 2006, 2007). In this thesis, ‘panpleurodire’ and ‘pleurodiromorph’ (after Lee 1995; Joyce et al. 2004) are used interchangeably. Pleurodiromorpha defined as ‘extant pleurodires and all fossil taxa more closely related to these than to extant cryptodires’ (Lee 1995) is synonymous with Panpleurodira (Joyce et al. 2004). Gaffney et al. (2006) recognize only Pleurodira: Minipleurodira + Megapleurodira.

The discovery in of cleithra (Joyce et al. 2006), loss of which is a cryptodiran synapomorphy, precipitated removal of Kayentachelys from Cryptodira. Cleithra are now known in a number of basal turtles. Further problems concern structures that closed the cranioquadrate space and braced the primary neurocranium; and jaw trochlear mechanics, involving sequences of development of the vertical pterygoid flange, the pleurodiran pterygoid trochlear and the otic trochlear of cryptodires (Gaffney et al. 1988; Gauthier et al. 1989; Gaffney 1996; Joyce 2007; Sterli et al. 2007; Gaffney et al. 2007; Sterli 2008). In cladistic topologies obtained by Dryden (1988), Joyce (2007) and others, features that usually support monophyly of the Pleurodira appear as derivatives of cryptodiran structures.

Patterns of cranial circulation in turtles have been intensely scrutinised recently (Jamniczky and Russell 2004; Jamniczky et al. 2006), investigations of primary homologies and their systematic utility focusing on transitions that are comparatively well illustrated in the cryptodiran record, across a broad range of extinct, mainly northern hemisphere groups. By way of contrast, the fossil record and documentation for archaic pleurodires is limited, in terms of both crania and postcrania. Classic texts on skull morphology in extant pleurodires include Schumacher (1973) and Albrecht (1976). The situation has gradually improved, with details of cranial morphology now available for early pelomedusoids such as barrettoi Meylan 1992, Brasilemys josai Lapparent de Broin 2000, and Euraxemys essweini and Dirqadim schaefferi Gaffney et al. 2006. As yet, however, no equivalent documentation exists on

6 cranial circulatory and nerve systems in the Chelidae, let alone in pleurodiran ancestors.

The paucity of Triassic records causes difficulty, as does the extended vacuum in the record between Proterochersis (Late Triassic) and the Late Jurassic to Early Cretaceous platychelyids. The only pre-Cretaceous pleurodire known from both crania and postcrania is Notoemys laticentralis Cattoi and Freiberg 1961. Absence of cranial information for basal pleurodires creates problems in distinguishing autapomorphies in Proganochelys from plesiomorphies shared with Proterochersis and Palaeochersis (Gaffney and Meylan 1988; Gaffney et al. 1991; Lee 1997; Shaffer et al. 1997; Hirayama et al. 2000; Lapparent de Broin 2001). Numerous studies over the past decade show that pleurodires had a far more interesting and diverse history than previously indicated (Meylan 1996; Gaffney et al. 2001; Lapparent de Broin 2000; Lapparent de Broin and Fuente 2001; Fuente 2003; Gaffney et al. 2001a, 2001b; Gaffney et al. 2002a, 2002b, 2002c; Gaffney et al. 2003; Rueda and Gaffney 2005; Gaffney et al. 2006). This sets the scene for major surprises and upheavals in evolutionary hypotheses as the fossil record becomes better known.

By the Aptian-Albian, major cryptodiran groups were emerging around the globe in a ‘rapid series of cladogenic events ... suggestive of starburst radiations’ (Shaffer et al. 1997), and across South America and Africa, pleurodiran diversity was increasing sharply (Lapparent de Broin 2001; Gaffney et al. 2006). The variety of groups apparent at this time suggests ancient divergences and multiple ghost lineages during the Mesozoic.

Although the earliest stages of turtle evolution are virtually uncharted, the list of basal taxa is expanding dramatically. Due to time constraints, data from important recent discoveries is excluded from this present study ( semitestacea Li et al. 2008; Chinlechelys tenertesta Joyce et al. 2008; and Eileanchelys waldmani Anquetin et al. 2008) – an indication of the speed of current dynamics. Relevant groups range from Late Triassic to , reflecting extreme temporal disjunction in the fossil record and evolutionary longevity within turtledom. Key taxa are: Proganochelys quenstedti Baur 1887; Palaeochersis talampayensis Rougier et al. 1995; africanus Gaffney and Kitching 1995; Proterochersis robusta Fraas 1913; Indochelys

7 spatulata Datta et al. 2001; Kayentachelys aprix Gaffney et al. 1987; Condorchelys antiqua Sterli 2008; Heckerochelys romani Sukhanov 2003; Mongolochelys efremovi Khozatskii 1997; bajazidi Nopsca 1923; and the platychelyids Platychelys orbendorferi Bram 1965, Notoemys laticentralis Fernandez and Fuente 1994, N. zapatocaensis Rueda and Gaffney 2005, and Caribemys oxfordiensis Fuente and Iturralde-Vinent 2001.

Meiolania platyceps figures prominently and contentiously in these deliberations. Palaeontologists have paid homage to the horned turtles for over a century and the group has endured a turbulent scientific history. Initial discoveries in South America and Australia involved flamboyant rivalry between palaeontologists and adventurers, unprovenanced and lost specimens and a series of misidentifications (Ameghino 1898; Moreno 1898). Meiolaniid skull material from Queensland was first reported as Megalania prisca, an extinct horned lizard (Owen 1881) and a tail club was also referred to Megalania with the footbones of a diprotodon (Owen 1882). Owen (1886) published figures of three skulls from Lord Howe Island, erecting the Meiolania to include M. platyceps and M. minor, the type material of which has disappeared (Gaffney 1983). Huxley (1887) described M. platyceps as a cryptodiran turtle, renamed as Ceratochelys. Unfazed, Owen (1888) referred another skull to Megalania, a combination turtle-varanid-diprotodon assigned to the suborder Ceratosauria.

Woodward (1888) separated turtle, lizard and , demolished Ceratochelys, synonymised M. minor and M. platyceps and referred the Queensland material to owenii. Etheridge (1889) described meiolaniid fragments from New South Wales and Lydekker (1889) published figures of the Meiolania type in the British Museum. Equivocal and/or misinterpreted features in the Lord Howe Island material created ongoing furore - Boulenger (1887, 1889) and Woodward (1901) argued that Meiolania is a pleurodire, on quadrate contact with the basisphenoid and absence of prefrontal- vomer contact, smooth otic chamber, closed tympanic cavity, cervical features and fusion of ilium and carapace. Baur (1889) and later Simpson (1938) assigned the group to the Cryptodira on presence of prefrontal-vomer contact, lateral upturned expansion of the pterygoids, rearward pterygoid extension and presence of an epipterygoid.

8 Anderson (1925) subsequently relegated the meiolaniids to the Amphichelydia, a kind of ‘turtle-too-hard’ taxon (Romer 1956) where they remained until placed in the Eucryptodira among modern forms, following monumental osteological and phylogenetic work by Gaffney (1983; 1985; 1990; 1996).

The comparatively scrappy meiolaniid material from South America is also contentious. Identification of Late Cretaceous meiolaniids from Argentina is disputed (Gaffney 1996). Specimens include a and peripheral bones from Patagonia (Los Alamitos) diagnosed cf Niolamia (de Broin 1987), as well as fragments from the ‘Alamitian’ of Rio Negro (de Broin and de la Fuente 1993), and a possible skull horn from the La Colonia Formation (Marcelo de la Fuente persn. commun.). It now appears that caudal vertebrae and shell remains from Rio Negro (Late Campanian-Early Maastrichtian) may indeed represent the oldest record for the Meiolaniidae (Sterli and de la Fuente. In Press). The oldest skull material for Meiolaniidae is the neotype of Niolamia argentina Ameghino 1899 from the Eocene or Late Cretaceous of Patagonia (Ameghino 1898; Moreno 1898; Woodward 1901). Niolamia is synonymised with Crossochelys corniger Simpson 1937 from the Eocene Casamayor Formation of Chubut by Gaffney (1983; 1996). Discovery of Early Cretaceous meiolanoids in Australia gives additional credence to the contested identifications in the Late Cretaceous of South America.

The previous oldest Australian record for meiolanoid turtles is Late . In , the Namba Formation of Lake Pinpa and the Etadunna Formation of Lake Pitikanta (Woodburne et al. 1993) have produced fragments sufficent to suggest taxa different from M. platyceps (Gaffney 1996). Miocene material occurs at Gulgong, New South Wales (Etheridge 1889) and the Wipajiri Formation of Lake Ngapakaldi in South Australia has yielded a single cervical rib (Gaffney 1981; 1996). Megirian (1989) reported a meiolaniid from the Bullock Creek Local Fauna (Miocene) of the Camfield Beds, and described Meiolania brevicollis Megirian 1992. The Miocene Carl Creek of Riversleigh, north Queensland, has produced important skull material consisting of the type of Warkalania carinaminor Gaffney et al. 1992 and the new braincase described in Chapter Five. Horned turtle elements are appearing at a number of Riversleigh sites (Henk Godthelp pers. comm.) and up to four

9 new taxa are indicated - ‘low in abundance despite their high diversity; four in two genera’ (White 1997: 420).

Pleistocene meiolaniids are better known. On the mainland, two giant forms were present in the Pleistocene of Queensland – the huge skull of Ninjemys owenii Woodward 1888 is from the Darling Downs (Bartholomai 1976; Gaffney et al. 1992), and in the north, horn scraps and a caudal vertebra from Wyandotte Station 45000 to 200000 years old, are described and identified as Meiolania cf. M. platyceps (Gaffney and McNamara 1990; Gaffney 1996). Meiolania mackayi Anderson 1925 from Walpole Island near is based on horn cores from phosphatic coral rock assumed to be Pleistocene or Holocene in age (Gaffney 1996); and a chip of cervical vertebra is known from Tiga Island in the Loyalty Group, New Caledonia (Gaffney 1996).

Over the past 120 years, large public collections have accumulated of meiolaniid material from South America, the Pacific Islands and mainland Australia. Specimens of Meiolania now comprise more than a dozen skulls, eight or nine braincases, cranial fragments and a hundred or more postcranial elements, mostly held at the Australian Museum in Sydney.

It must be emphasized however that certain crucial areas of the skeleton are not preserved in the Lord Howe Island material, and that crania and postcrania for other Tertiary meiolaniids is problematic and very sparse. Osteological details that are either unknown or ambiguously preserved in Meiolania include: i) the palate, which is extremely fragile and thin-boned, with fused sutures and parasagittal perforations that are asymmetrical and variable between individuals (Gaffney 1983: 390: 21; 424: 42); ii) the temporal skull roof in which sutures are fused rear of the orbital fossae (Gaffney 1983: 390: 21); iii) the number and shape of neurals, and configuration of marginal and vertebral scutes of the anterior carapace (Gaffney 1996: 24: 19, 20); iv) exact layout and number of costals, and pygal region (Gaffney 1996: 10: 5, 6); v) the plastron, in which many sutures are fused (Gaffney 1996: 34: 27, 28).

10 Otwayemys and the meiolaniids were tenuously united in several analyses, assumed to share common ancestors with the ‘sinemydid-macrobaenids’, Late Jurassic Asian and North American eucryptodires that developed in the Laurasiatic part of Pangea (Gaffney 1996, 1998; Lapparent de Broin and Molnar 2001; Gaffney et al. 2007). Chelycarapookus was reportedly ‘similar in many features to sinemydids’ (Gaffney et al. 1998). Some recent studies position the meiolaniids at a more basal level (Hirayama et al. 2000; Joyce 2007; Sterli 2008), but subsequently, Chubutemys from Patagonia was compared by its authors to the ’usual suspects‘, including the primitive macrobaenid Judithemys sukhanovi Parham and Hutchison 2003 from North America. Chubutemys was resolved as sister taxon to Otwayemys and the meiolaniids, which were internested once again with the northern hemisphere eucryptodires (Gaffney et al. 2007).

Gaffney’s work on meiolaniids (1983, 1985, 1996; Gaffney et al. 1984, 1992, 1998) is a legacy of outstanding observational, descriptive and analytical skill, yet he was first to acknowledge that his diagnosis of relationships relies almost entirely on Meiolania from Lord Howe Island. All previous analyses of the meiolaniids were based on data from this taxon, arguably the most derived member of the group.

Discovery in the Albian of eastern Australia of a diversity of primitive meiolaniid-like forms and chelid pleurodires raises important issues. These turtles provide novel information on structural progressions in stem groups and morphology and timing of the primary ‘casichelyidian’ dichotomy (Chapter Nine), biology and biogeography of Mesozoic turtles (Chapters Eleven and Twelve) and turtle origins (Chapter Thirteen).

The cladistic analysis presented here is heuristic and by no means conclusive, and debate on the phylogenetic status of the meiolaniids will surely continue, perhaps with renewed vigour in the near future. It seems axiomatic that primitive southern hemisphere groups are most relevant to determination of affinities of terrestrial and freshwater turtle populations in near-polar . Evidence for great antiquity of the horned turtles is in stark contrast to current phylogenetic theories. This highlights the vast temporal and structural unknowns in early turtle evolution, and its enthralling potential for surprises.

11 TERRESTRIAL AND FRESHWATER TURTLES OF EARLY CRETACEOUS AUSTRALIA

ELIZABETH T. SMITH Research Associate The Australian Museum, Sydney

A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy

February 2009

Vertebrate Palaeontology Laboratory School of Biological, Earth and Environmental Sciences University of New South Wales, Sydney

CHAPTER TWO

SPOOCHELYS ORMONDEA N. FAM., GEN. ET SP. (MEIOLANOIDEA: SPOOCHELYIDAE) – AN ARCHAIC MEIOLANIID-LIKE LAND TURTLE FROM LIGHTNING RIDGE, NEW SOUTH WALES, AUSTRALIA

Spoochelys ormondea n. fam., gen. et sp., from the middle Albian Griman Creek Formation of northwestern New South Wales, was a small to medium sized terrestrial turtle (~1 m) with a domed carapace, strongly-bound lower forelimb elements, and very short hands and feet. Spoochelys is anachronistically archaic, retaining the postparietal, supratemporal and interpterygoid vacuity, structures identified previously only in Triassic/ turtles. A sister-group relationship with the Meiolaniidae is soundly supported by a suite of shared cranial and postcranial derivations. Spoochelys is assigned to the new family Spoochelyidae, sister-group to the Meiolaniidae, in the superfamily Meiolanoidea. Sunflashemys bartondracketti n. gen. et sp. and Opalania baagiiwayamba n. gen. et sp. from Lightning Ridge, are also assigned to the Spoochelyidae.

Gaffney (1983, 1985, 1996) and Gaffney et al. (1996, 1998; 2007) interpret the Meiolaniidae as eucryptodiran turtles within the Centrocryptodira (of Gaffney and Meylan 1988). This is contested by other workers who locate the horned turtles among basal cryptodires (Hirayama et al. 2000), or pancryptodirans or cryptodiromorphs outside the (Joyce 2007; Sterli et al. 2007; Sterli 2008).The fossil record for earlier members was non-existent until these recent discoveries at Lightning Ridge, which provide evidence in contradiction of both prevailing hypotheses on meiolaniid relationships.

Temporal disjunction in the fossil turtle record is not unusual. Heckerochelys from Russia is ‘the youngest member of the so-called ‘Triassic generation of turtles’’ (Sukhanov 2006: 117). The Late Cretaceous cryptodiromorphs

13 Kallokibotion from Roumania (Nopsca 1923; Gaffney 1982) and Mongolochelys from China (Khozatsky 1997; Sukhanov 2000) are also anachronistic. Among pleurodires, Notoemys zapatocaensis (Rueda and Gaffney 2005), a late-surviving platychelyid from Early Cretaceous Columbia, is comparable. The morphologic/stratigraphic disparity is exceptional in the case of Spoochelys.

The holotype specimen of Spoochelys, a near-complete skull (Figs. 2, 3, 4), and the paratype, a partial braincase (Fig. 5) were discovered in the early 1990’s by opal miner Ormie Molyneux. Both specimens were recovered on the Coocoran opal fields west of Lightning Ridge - the skull from an area of Olga’s Field known as Spook’s, and the braincase probably from Emu’s Field, although the exact site is uncertain. The braincase was badly damaged in the mining machinery. Fortunately, the skull was encased in very hard silicified sandstone which prevented its destruction when the opal dirt was extracted and processed. This specimen is complete, apart from the snout and a section of the dermatocranium, preserved in dark grey potch (common opal) which is partly transparent and displays iridescent blue and green opal colour across the temporal roof. The specimen was prepared using a Dremel-type handpiece with a very fine diamond-point. Details of the temporal roof are more precisely preserved than the basicranium, and the interorbital and subtemporal fossae and cavum cranii are still filled with siliceous claystone.

Turtle material at Lightning Ridge survives the mining process due to the robust nature of the skeleton, and vertebrae and upper limb bones are the most durable postcranial elements. When groups of specimens are confidently assessed to have been associated or articulated prior to excavation during opal mining, taxonomic separations of material from other locations can be made by cross referencing and extrapolation. Elements of the axial series of Spoochelys are often associated with shell material, particularly peripheral bones that are distinguished by the same fine rasp-like texture that characterizes the dermal roof of the type skull. Unfortunately, costal elements and plastron fare very badly in the mining machinery and uninformative shards of badly smashed are relatively common. Consequently, the shell of Spoochelys is very poorly known (Figs. 7, 8).

14 SYSTEMATIC PALAEONTOLOGY TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996 Family SPOOCHELYIDAE n.

Type genus. Spoochelys, n. gen. Included genera. Spoochelys n. gen.; Sunflashemys n. gen.; Opalania n. gen. Distribution: Albian, New South Wales, Australia. Diagnosis: A member of the Superfamily Meiolanoidea. The family Spoochelyidae is characterised by extended basisphenoid margin of open cavum labyrinthicum formed by basisphenoid shelves dorsal to ventral plane of the basicranium; cavum acustico-jugulare, cavum labyrinthicum and recessus scalae tympani without bony floor; foramen caroticum basisphenoidale = foramen posterius canalis carotici interni; posterior cervical vertebrae with tall posterior central facets and very tall neural arch placing postzygapophyses rear of centrum; sixth and seventh cervical vertebrae with parapophyses extending anterior to central facet; tenth thoracic vertebra centrally fused with sacrum; one sacro-caudal vertebra. (These characters are known only for Spoochelys and Sunflashemys).

Spoochelys n. gen. Diagnosis. As for only known species. Etymology. ‘Spook’s’ for the opal-field location of the type skull (Appendix 2.0.4); and ‘- chelys’ for turtle.

Spoochelys ormondea n. gen., n. sp. (Figs. 2-16) Type specimen. Australian Opal Centre, Lightning Ridge, plastoholotype LRFR450. Australian Opal Centre, Lightning Ridge, plastoparatype LRFR451. These two specimens are replicas in Hydrostone of the original specimens, which are in private ownership.

Locality and horizon. Finch Claystone Facies of the Wallangulla Sandstone Member of the Griman Creek Formation. Early - middle Albian (Exon and Senior 1976; Morgan 1984; Burger 1986, 1995); middle - late Albian (Dettman et al. 1992).

15 Etymology. ‘ormondea’ for opal miner Ormie Molyneux who discovered and still owns the original specimens.

Diagnosis: Primitive terrestrial turtle. Skull fully roofed; cheek slightly emarginated; very large orbits. Cranial scute pattern as in Meiolania - small scale X and scutes B, C, D, E, F, G, H, J and K present; scutes with small rounded linearituberculate ridges arranged radially and rostrocaudally; temporal margin probably faintly spinous; cheek area and carapace bones decorated with small irregular polygons enclosing punctation clusters; triangular postparietal acuminate anteriorly, demarcated by scute texture and deeply incised scute sulci; postorbital-prefrontal contact prevents frontal contribution to orbit; postorbital nearly bisects quadratojugal on edge of cavum tympani; supratemporal subcircular and separated from rear temporal margin, contacting postorbital and quadratojugal; supraoccipital broadly expanded across otic chamber, reaching margin of foramen stapedio-temporale; large R-shaped epipterygoid; squamosal large posteroventrally; precolumellar fossa broad and shallow; three or more prominent elliptical supramarginal scales on anterolateral carapace edge (as in Palaeochersis) reducing intervening marginals; seventh cervical vertebra biconcave with large parapophyses and triangular posterior cotyle; chelid- like cervical features (posterior cervicals with tall central articulations, elevated neural arch, postzygapophyses posterior to centrum); tenth thoracic vertebra centrally fused with sacrum; posterior caudals with long haemal keels curving posterior to centra.

Differs from Sunflashemys in details of basisphenoid, pterygoids and basioccipital, articular surface of lower jaw, anterior carapace margin, axial skeleton and pectoral girdle; differs from Opalania in lower jaw, anterior carapace margin and unguals; differs from Chelycarapookus in finer carapace and plastron ornamentation; differs from Otwayemys in surface texture of dermal roofing elements and features of cavum tympani, maxilla, lower jaw, anterior peripherals and cervical vertebrae.

Referred specimens. Cranial elements: partial left quadrate, AMF121643; supraoccipital, AMF121646; epipterygoid, LRF61; quadrate, LRF62. Carapace and plastron: AMF121579, AMF121581, AMF121580, AMF128001, LRF341, LRF343,

16 LRF344. Cervical vertebrae: third AMF127984, AMF127990; fourth AMF68254, AMF112750; fifth LRF464; seventh AMF127972, AMF127996, LRFR465; eighth AMF72276, LRFR466. Sacral, sacro-caudal and caudal vertebrae: LRF407, AMF127978, LRF16, LRFR467, AMF66772, LRFR468, LRFR469; AMF121638, AMF121603, LRFR470. Pectoral girdle: AMF66776, AMF66777, AMF127942, AMF121587. Humerus: AMF68310, AMF(unreg.MH), AMF68321, AMF73508, AMF127956, LRF78, and AMF127940. Ulna: AMF127944, AMF121621, LRF79, LRFR471, LRFR472. LRF79. Pelvic girdle AMF121622, AMF66778, AMF127949, AMF66779, AMF66774, AMF127991, AMF127948, AMF121614, AMF128002. Femur: AMF67885, AMF112753, AMF121616, AMF121618, AMF12124, AMF127943, LRF46, LRF84, LRF1216, LRF184, LRF532, LRF696AE, LRF747, LRF84, LRF338, LRFR452, LRF339. Tibia: AMF112828, LRF85, LRF1095, LRF1227, LRF731, LRF745, AMF1227958. Carpus, tarsus, manus and pes: AMF127961, AMF121613, AMF127966, AMF127962, AMF121964, AMF121963, LRF82.

Description and comparison Skull (Figs. 2, 3, 4, 5, 6) The following description is based primarily on the original near-complete specimen, which is adequately recorded as cast LRFR450, and photographically. Dermal bones are missing from the snout, dorsoventral compaction has forced the temporal roof down and the lower jaw up, and palatal structure is indistinct. The snout is pointed and the skull is triangular, broad posteriorly and fully roofed. Cheek emargination is slight. Orbits are directed predominantly laterally and are very large (orbits = 16 mm; skull length = 48 mm). The original paratype specimen (recorded as cast LRFR451) consists of a section of dermal skull roof and otic chambers, broken anterior to the parietal-frontal suture through the front of the basisphenoid. In this specimen, the front of the cavum cranii is very high and box-like, and the rear section of the dermal roof is missing. Although the skull specimens are consistent in size with most turtle material in the Lightning Ridge assemblage, it is possible that they represent juvenile or immature .

Cranial scutes (Figs. 3, 4, 39)

17 Scutes and bones of the skull roof are fused, as in meiolaniids (Simpson 1938; pers. obs.). Scute sulci are straight and incised. Scute texture in LRFR451 was abraded during mining, but the internal microstructure is clearly visible, showing that in this specimen also, scute and bone are fused horizontally. In LRFR450, low tuberculate ridges radiating from the pineal area are heavier at the rear and probably extended as small spines from the temporal margin.

Scute layout, described here as for meiolaniids (after Gaffney 1983, 1996), is clearly preserved in LRFR450. Scute margins correspond closely with bone margins. The small central diamond-shaped scale X on the parietal is bordered by pentagonal scales G on the frontals, which adjoin X anterolaterally. D scales on the parietal are subdivided into D1 medially and D2 laterally. Scales D1 meet on the midline, rear of scale X, separated posteriorly by triangular scale A. Scale F adjoins scale G anterolaterally on the edge of the orbit. Medially, single scale Y represents the posterior part of the frontal. Scales H and C overly the postorbital. Scale B represents the supratemporal and squamosal on the rear outer skull corner. J2 on the jugal is large and circular, J1 and scale I cover the quadratojugal and maxilla respectively.

Scales X, B, A, D and G of Spoochelys correspond with 10, 9, 8, 7 and 6 respectively of Proganochelys SMNS16980 (Gaffney 1990). Proganochelys, Spoochelys and the Australian meiolaniids share the small central diamond-shaped X scale at the parietal-frontal contact and median scale Y on the frontals. Scales X, B, C, D, G, H, E, J, K and I of Spoochelys closely match those of Meiolania in size, shape, contacts and position. This pattern is synapomorphic for meiolaniids (Gaffney 1996).

Cheek scales are thinner, textured with irregular incised polygons and tiny ‘pin- point’ fossae, a chelid-like decoration. These two distinctive ornamentations are repeated, with some variability, in carapace and plastron – the linear ridged texture on peripheral bones, and the polygonal pattern on the costals and plastron.

Maxilla

18 The maxilla extends briefly into the orbital floor, is narrow below the orbit and slightly curved. The contact with the jugal runs horizontally from the orbital margin, so the rear exposure on the cheek is acuminate as in Meiolania. As in Palaeochersis, the maxilla separates the anterior section of the jugal from the cheek margin (Sterli et al. 2007).

Palatine On the dorsal surface, the palatine-pterygoid suture appears to run forward from the median edge of the foramen palatinum posterius, meeting the palatine-vomer suture which extends forward from this. As in Meiolania, the foramen palatinum posterius is in the rear floor of the orbit. Location of the foramen palatinum posterius behind the orbit is a pleurodiran synapomorphy (Gaffney and Meylan 1988).

Jugal Large and subcircular, the jugal constitutes about one third of the orbital rim, with a small vertical posterior contact with the quadratojugal on the cheek, and a longer contact with the postorbital. The semicircular rear margin resembles Meiolania but the posterior extent is greater in Spoochelys. Ventrally the jugal is slightly emarginated, so the ventral edge of the skull curves convex posteriorly and concave anteriorly.

Quadratojugal The long narrow C-shaped quadratojugal encircles most of the cavum tympani, extending ventrally below the incisura columellae auris and contacting supratemporal and squamosal dorsal to the incisura. A similar degree of quadratojugal extension dorsal to the stapes articulation with the quadrate is present in Proganochelys, but there is no evidence elsewhere among turtles of a quadratojugal-supratemporal contact.

The quadratojugal is almost divided by the postorbital on the edge of the cavum tympani. A small opening between quadratojugal, jugal and postorbital resembles Proganochelys SMNS16980 which has a space between quadratojugal and jugal on

19 the cheek (Gaffney 1990). Kordikova (2002) argues that SMNS16980 is a juvenile; perhaps this feature in Spoochelys is ontogenic.

Nasal and prefrontal Dermal bones of the snout are missing. Presence/absence and size of nasal bones cannot be determined, and it is unclear if prefrontals met on the midline. The prefrontal forms the anterodorsal orbital margin and contacts the postorbital on the posterodorsal orbital rim.

Frontal Missing the anterior margins, the frontals are relatively large and wedge-shaped, excluded from the orbital rim by prefrontal-postorbital contact, the primitive condition. The frontals partly separate the parietals, a resemblance to Proganochelys (Gaffney 1990; Kordikova 2002).

Postorbital Forming the posterodorsal margin of the orbital fossa, the postorbital contacts the jugal ventrally and supratemporal posteriorly. Posteroventrally, there is a long contact with the quadratojugal. A postorbital-quadratojugal contact has been identified in Proganochelys (Kordikova 2002), and is present in Palaeochersis, Kayentachelys, meiolaniids, baenids and pelomedusoids.

Posteromedial extent of the postorbital is difficult to establish in Spoochelys and two interpretations are possible. The postorbital may be fan-shaped, expanded posteromedially, reducing the size of the parietals, although not reaching the rear temporal margin, and forming the entire anterior edge of the supratemporal. Conversely, the postorbital may be narrower, with a smaller contact with the supratemporal. In this case, the parietal contacts the supratemporal. This latter condition would resemble Proganochelys (Kordikova 2002) and Palaeochersis. Either way, among turtles the postorbital-supratemporal contact is unique to Spoochelys.

Parietal

20 As in Proganochelys (after Kordikova 2002: 207: 2A), parietals are subdivided at the rear by the postparietal. The parietal contacts the postorbital anterolaterally and laterally and may contact the supratemporal posterolaterally. The parietals extend forward slightly between the frontals. The processus inferior parietalis is short, contacting epipterygoid, prootic and supraoccipital. Spoochelys resembles Meiolania and Kayentachelys (Sterli and Joyce 2007) in absence of bony cavum epiptericum and exclusion of the parietal from the trigeminal foramen. In more advanced turtles, the parietal contacts the crista pterygoidea.

Postparietal In LRFR450, the arrow-shaped postparietal is sutured along the top of the rear braincase wall. This suture is also evident in LRFR451 in which the postparietal is missing, apparently due to post-excavation damage. LRFR450 shows a pronounced indentation, perhaps exaggerated by post-mortem compaction, at the front of the postparietal on the midline, in the position of the primitive pineal foramen. Paired postparietals are identified with hesitation in Proganochelys (Kordikova 2002), the only previous report of this element among turtles. Presumably the element in Spoochelys is paired. The temporal rim is fractured and abraded, so presence of tabulars cannot be determined with certainty.

Supratemporal The supratemporal is subcircular, separated from the temporal margin by the squamosal, contacting quadratojugal posteroventrally, postorbital anterolaterally and perhaps laterally, and possibly the parietal medially. The condition differs from Proganochelys (Gaffney 1990; Kordikova 2002) and Palaeochersis (Sterli et al. 2007) because the supratemporal is located forward of the squamosal. Supratemporal contact with the quadratojugal and postorbital are otherwise unknown among turtles, however supratemporal-postorbital contact is seen in captorhinomorphs and eosuchians (Romer 1956). The supratemporal is lost in turtles above Palaeochersis and Australochelys.

Squamosal

21 The squamosal contacts the parietal medially, supratemporal and quadratojugal anteriorly and enters the rear rim of the cavum tympani. Position of contact with the opisthotic is unclear, however the squamosal descends posteriorly, contributing to the heavy buttress of bone behind the incisura columellae auris.

Supraoccipital The supraoccipital forms the dorsal rim of the foramen magnum and a very short crista supraoccipitalis but is not exposed on the dermal roof. This is confirmed by LRFR451 and AMF121646, an isolated supraoccipital. Meiolania supposedly has a large exposure of the supraoccipital on the skull roof, however Gaffney’s (1983) reconstruction is tentative. There is a small supraoccipital exposure in Mongolochelys but none in Kayentachelys. In Spoochelys, the supraoccipital flares ventrally across the otic chamber as in Notoemys, reaching the posterior edge of the foramen stapedio temporale as in Meiolania.

Quadrate The quadrate contacts the prootic on the anteroventral surface of the otic chamber, but the anteroventral contact with the pterygoid is not defined. The front of the otic chamber is narrow and unexpanded, the lower edge an abrupt angle: there is no evidence of the cryptodiran processus trochlearis oticum. Quadrate-quadratojugal contact forms most of the periphery of the cavum tympani, which is well developed, however the incisura columellae auris is above, not medial to, the mandibular condyle. The incisura is open posteroventrally, incorporating stapes and eustachian tube, as in meiolaniids, pleurodires and some primitive cryptodires. A wide hemispherical precolumellar fossa is divided from the inner chamber of the cavum tympani and as in many extant chelids, this anterolateral section of the cavum can be seen in occipital view (pers. obs.; Gaffney 1979). The quadrate curves behind and below the incisura. The mandibular condyle is a deep block with a concave articular surface that is located forward of the basisphenoid-basioccipital suture as in primitive pleurodires (Gaffney et al. 2006).

Opisthotic

22 The opisthotic forms the posterolateral section of the otic chamber, the paroccipital process contacts the exoccipitals ventrally and the opisthotic-supraoccipital suture runs anterolaterally across the roof of the otic chamber, apparently reaching the foramen stapedio-temporale. Ventrally, the opisthotic-exoccipital suture diagonally traverses the roof of the recessus scalae tympani. Visible from below, the base of the processus interfenestralis is free, contacting the basisphenoid-basioccipital suture. As in Meiolania, the opisthotic-quadrate suture crosses the roof of the cavum acustico- jugulare anteromedially, reaching the medial ceiling of the aditus canalis stapedio temporalis. This is apparently more primitive than the condition in Notoemys, in which the aditus is formed between quadrate and prootic. The condition is undocumented in Heckerochelys.

Exoccipital Forming the lateral margin of the foramen magnum, the exoccipital is widely separated from the occipital condyle. In both skull specimens, the foramen jugulare anterius is inaccessibly concealed in matrix, and the foramen jugulare posterius is unformed as in turtles below Kayentachelys (Rougier et al. 1995) including Heckerochelys (Sukhanov 2006). Although hidden in occipital view by the exoccipital, the recessus scalae tympani is open ventrally as in Notoemys laticentralis (Lapparent de Broin 2000) and Heckerochelys (Sukhanov 2006). The rear wall of the exoccipital is strongly indented and the foramina nervi hypoglossi pierce the exoccipital-basioccipital suture. A similar condition is seen in turtle cranial material from Inverloch, Victoria and in the meiolaniid cf. Warkalania from Riversleigh (although not in Sunflashemys). In Proganochelys and other turtles, the hypoglossal foramina pierce the exoccipital. The condition in the Australian taxa may be closer to that of primitive , in which the vagus nerve, of which the hypoglossal is a component, usually passes between opisthotic and exoccipital (Romer 1956).

Basioccipital The basioccipital is robust and blocky, forming the posteromedial lower margin of the cavum labyrinthicum. The basioccipital tubercles differ from Sunflashemys in being smaller and aligned anterolaterally (that is, more widely separated at the front)

23 and are linked posteriorly by a curved web of bone. The neck of the occipital condyle is short, the articular surface is subtriangular and flattish with a strong ventral lip.

Epipterygoid In Spoochelys, the epipterygoid is a prominent triangular element, rod-like dorsally, contacting the parietal dorsally and the prootic posterodorsally by a short vertical suture above the foramen nervi trigemini. Ventrally, the epipterygoid is laminate with a long straight contact with the pterygoid. The epipterygoid dips anteriorly, descending below the level of the basisphenoid rostrum and possibly contacting the anterolateral section of the basisphenoid as in Sunflashemys. In LRFR450 and LRF61, a posterolateral suture with the quadrate is discernible but the trigeminal foramen may be continuous with the large fossa cartilaginus epipterygoidei: the preservation is ambiguous. However in LRFR451 there is a well-developed suture and the fossa cartilaginous epipterygoidei is absent. In LRFR450, the epipterygoid forms most of the posteromedial margin of the infraorbital fossa and the entire anterior and ventral margin of the foramen nervi trigemini, and sends a pronounced semicircular flange forward of the processus inferior parietalis. Epipterygoid morphology of Spoochelys closely resembles that of Meiolania, particularly the triradiate cross-section of the dorsal section and anterolateral dorsal flange.

Ossifications of the front braincase wall in reptiles are problematic and the reptilian pleurosphenoid is often considered analogous to the laterosphenoid and epipterygoid (Rieppel 1992). In Proganochelys, the large R-shaped element projecting into the lower orbital fossa was identified by Gaffney (1990: 72) as a ‘pleurosphenoid’. It was argued that this element is not homologous with the pleurosphenoid of other reptiles but is an independent ossification of the planum supraseptale, on grounds of similarity to the persistent adult cartilage of the planum in Chelonia, Dermochelys and (Gaffney 1990: 58-59: 47, 48). The proganochelyid ‘pleurosphenoid’ was thus interpreted as autapomorphic (Rieppel 2000). With some hesitation, Sterli and Joyce (2007) identified a ‘laminar bone with rounded edges’ in one skull specimen of Kayentachelys as a pleurosphenoid. However the epipterygoid of Kayentachelys TMM43670-2 resembles both the proganochelyid ‘pleurosphenoid’

24 and the epipterygoid of Spoochelys. In Kayentachelys, the trigeminal foramen is open and the epipterygoid protrudes diagonally into the subtemporal fossa (Sterli and Joyce 2007). In Spoochelys, the epipterygoid is fixed to the parietal and prootic dorsally, closing the trigeminal foramen, and the flange into the fossa temporalis is rounded rather than acute. The dorsolateral extension of the epipterygoid of Spoochelys is thus an appropriate intermediate between the ‘pleurosphenoid’ of Proganochelys and the epipterygoid of Kayentachelys. In the context of other primitive elements shared by Proganochelys and Spoochelys, it seems reasonable to reidentify the ‘pleurosphenoid’ of Proganochelys as the epipterygoid.

Prootic On the front of the otic chamber, the prootic is a large subtriangular element contacting the epipterygoid dorsal and ventrolateral to the foramen nervi trigemini, thus forming the entire rear margin of that foramen, as in Meiolania. The prootic contacts the parietal dorsally and expands broadly across the front of the otic chamber, contributing to the anterior margin of the foramen stapedio temporale, which opens dorsally.

Ventrally, the exposed prootic forms the anterior wall of the cavum labyrinthicum and anteromedial margin of the cavum acustico-jugulare. Contact between the prootic and the processus interfenestralis of the opisthotic is limited and the fenestra ovalis is unfloored.

Pterygoid Both pterygoids are preserved in LRFR450, the right element partly concealed by the cornu branchiale. Post-mortem distortion may have severed pterygoid contact with the maxilla: if so, the foramen palatinum posterius was originally small and closed. Conversely, the condition may resemble Heckerochelys, which exhibits a small processus pterygoideus externus. The transverse pterygoid process on the left has a small spur. This is not a processus trochlearis pterygoidei, but a remnant of the poorly-preserved cornu branchiale which was removed during preparation to provide a view of the left pterygoid. Contact between pterygoid and epipterygoid runs along the lower edge of the otic chamber. Ventrally, the pterygoids contact on the midline

25 anterior to a bracket-shaped interpterygoid vacuity that is V-shaped at the front. The broad crescentic form of the vacuity is shared with meiolaniids, particularly Crossochelys. Possibly the depth of the gap has been reduced by post-mortem compaction, however the edge is unsutured and the pterygoid lamina is dorsoventrally separated from the basisphenoid.

The pterygoid abuts the basisphenoid to a point rear of the foramen basisphenoidale, then extends posterolaterally as a narrow vertical ribbon or strap along the medial section of the quadrate, reaching dorsal to the mandibular condyle. The pterygoid is very widely separated from the basioccipital, leaving the prootic strongly exposed. In Heckerochelys and Mongolochelys, the pterygoid reaches the cavum labyrinthicum and cavum acustico-jugulare.

It is likely that in Spoochelys, the canalis nervi facialis opens from the front wall of the cavum acustico-jugulare as in Sunflashemys, however the area is poorly preserved in both skull specimens.

Basisphenoid Basisphenoid details are clear in the holotype and in LRFR451. The basisphenoid is massive, and the flattish lower surface lacks the median crista seen in Sunflashemys. Well separated from the pterygoid, paired foramen caroticum basisphenoidale (= foramen posterius canalis carotici interni) are located level with the front of the otic chamber and the path of the external carotid artery is marked by grooves. At the rear of the basisphenoid, a faint transverse ridge sends triangular extensions onto the basioccipital tubercles so the contact with the basioccipital is weakly bilobial, and in LRFR451 these paired extensions form a W-shaped structure. Dorsal to this ventral basisphenoid surface, thick posterolateral shelves of the basisphenoid form the lower medial margin of the cavum labyrinthicum. The condition is very similar to Sunflashemys and Notoemys, differing starkly from Kayentachelys in which the cavum labyrinthicum is closed.

The anterodorsal section of the basisphenoid has not been prepared in the original skull specimen and the anterior part is missing in the paratype, however the latter

26 specimen preserves the dorsum sellae which is very high, angled anterodorsally and subdivided by a midline ridge that meets the rostrum basisphenoidale ventrally. It is possible that the paired carotid canals open in the ventral section of the dorsum sellae as in Kayentachelys, however this area is poorly preserved in both skull specimens. In Sunflashemys the internal carotid canals may extend forward with the rostrum basisphenoidale, and due to breakage, it is unclear if the canals open into the dorsum sellae.

Columella auris The stapes of Spoochelys is thick, aligned horizontally at right angles to the skull midline and was presumably supported by cartilage as there is no bone below the columella along its full length, apparently as in Notoemys. The footplate is expanded and the fenestra ovalis is perpendicular.

Hyoid The right cornu branchiale I is elongate and slender, cylindrical in cross section, tapering posteriorly. The rostrocaudal-posterolateral curvature seems unusual, resembling (Scumacher 1973) and cornu branchiale II of Meiolania (MMF13825a; Gaffney 1983: 424: 42).

Lower jaw The inner surface of the left mandible in the original skull shows a large splenial extending along the lower rim of the ramus and a long oblique splenial-prearticular contact. Dentary-splenial contact bridges the meckelian sulcus anterior to the foramen intermandibularis medius, a unique derivation also present in Meiolania and Opalania.

Carapace (Fig. 7) Only the front section of the carapace can be reconstructed. It is steeply vaulted and rounded anteriorly. The bones are thick with a fine linear surface texture and strongly vascular internal microstructure. The punctations and incised polygons of the cheek surfaces of the type skull are repeated on ventral carapace surfaces and plastron. This polygonal pattern is chelid-like, seen in Cretaceous chelids from

27 Patagonia (Lapparent de Broin and de la Fuente 2001) as well as modern forms (pers. obs.).

The cervical scute is barrel-shaped and wider than long and the first vertebral scute is semicircular. The first pleural sulcus is shallowly incised on the medial surface of the second peripheral, suggesting that vertebrals are wide and pleurals are elongated. The suture between the nuchal and first peripheral lies lateral to the cervical scute as in Notoemys zapatocaensis. The large posteroventral cavity in the second peripheral indicates that the axillary buttress extended far forward and was tightly curved.

The cervical scute abuts the first of a series of bulbous elliptical supramarginal scales on the carapace edge. These supramarginals alternate with marginals that are reduced to small triangular shelves between adjoining supramarginals. The medial supramarginal scale sulci are heavily incised and the supramarginals straddle peripheral sutures. Thus the first peripheral bears the front half of the first supramarginal, the second peripheral has the rear half of the first supramarginal and the anterior half of the second supramarginal, and the third peripheral carries the rear of the second supramarginal and the front section of the third supramarginal. The tiny marginals are contained within each peripheral, lateral to the supramarginal junctions.

Bridge peripherals are known for Sunflashemys, and isolated specimens AMF128022 and AMF127941 are referred to Spoochelys but cannot be positioned numerically. These bridge peripherals are narrow dorsally, very deep dorsoventrally and slightly guttered. Supramarginals appear to be retained as long tubercles or ridges. The carapace-plastron attachment was sutured and at least one of the more anterior bridge peripherals shows grooves for two costal rib ends, a distinctive derived feature that is shared with Sunflashemys, platychelyids (Notoemys laticentralis, N. zapatocaensis and probably Caribemys) and chelids. AMF128011, tentatively assigned to Spoochelys, is possibly a seventh or eighth peripheral. In this specimen, the dorsal surface is broadened with an edge that is slightly upturned. Low domes in the dorsal gutter may represent the anterior and posterior sections of two supramarginals. The medioventral edge has three small circular sockets for plastron attachment.

28 The carapace dome appears to be higher at the front and supramarginals may be less prominent in juvenile and immature individuals. There are at least three anterior supramarginals and possibly three supramarginals in the bridge region. Gaffney (1990) suggests that posterior marginals in Proterochersis may be supramarginals, and this may also be the case in Spoochelys, as supramarginals progressively impinge on the carapace edge, possibly obliterating the posterior marginals. Palaeochersis has three lanceolate supramarginals on the anterior carapace margin and paired tubercles at the rear of the carapace (Sterli et al. 2007) that are strikingly similar to the turret-shaped supramarginal that adjoins the eighth costal in Indochelys (pers. obs.; Chapter Six).

Structure of the visceral carapace surface is poorly known, however the first thoracic rib is fused to the costal bone, as in Sunflashemys, Chelycarapookus (Fig. 36, p. 140) and Notoemys laticentralis (Fernandez and de la Fuente 1994). In Meiolania, this attachment is apparently sutured in one specimen (Gaffney 1996) but fused in others. In Spoochelys, Sunflashemys and Chelycarapookus (Fig. 36), the first thoracic rib is very long, deep dorsoventrally and blade-like, strongly coalesced with the reduced second thoracic rib, and proximal sections of the rib shafts are cojoined, the condition again closely resembling Meiolania.

The tall neural spine of the eighth cervical vertebra terminates in a blunt subcircular facet for articulation with the carapace. No complete nuchal bone is known that is attributable to Spoochelys, however a nuchal nubbin for the spine of cervical eight is seen in NMVP208303, an anterior carapace from Inverloch (Victoria) that closely resembles NMVP199057. As in Spoochelys, these two Victorian specimens have distinctive elliptical supramarginal scales.

LRF407 (Fig. 9), an articulated pygal and suprapygal, shows that the suture between the two elements is V-shaped posteriorly as in Indochelys (pers. obs.; Fig. 33, p. 128) and Notoemys zapatocaensis (Rueda and Gaffney 2005), and that a low midline crest is developed in both elements, as in Notoemys.

Plastron (Fig. 8)

29 A partial plastron is attributed to Spoochelys on bone texture consisting of a reticulated network of fine polygons and small fossae. Details of the anterior plastral margin and entoplastron are indeterminate, and plastral scute sulci are absent. The hyoplastron is long and wide anteriorly, and is remarkably flat, axillary buttresses are unthickened, only slightly inflected above the ventral plastral surface as in Meiolania and extend far forward, almost level with the front of the plastron. Connection to the carapace was sutural along the mid-section of the bridge, supplemented by long peg- like processes anteriorly. Only the rear section of the epiplastron is preserved – it was large and acuminate, resembling that of Indochelys and Chelycarapookus. Mesoplastra appear to be absent, the suture with the hypoplastron is transverse and a small mid-plastral fontanelle may have been present, but this is not definite. The xiphiplastron is weakly bifid, with a thickened ischial base. In features such as the plastral ‘pegs’ and absence of mesoplastra, the plastron of Spoochelys resembles that of sinemydids, macrobaenids and other primitive Asian and North American eucryptodires, however in these northern hemisphere groups, the anterior plastral lobe is generally short and narrow at the front, and the entoplastron is comparatively small.

Cervical vertebrae (Figs. 10, 11) Cervical vertebrae of Spoochelys and Sunflashemys are very similar. Rear cervicals of Spoochelys have shorter, wider centra than those of Sunflashemys, and the posterior margin of the diapophysis is tilted dorsally (resembling Meiolania; pers. obs.; Gaffney 1985: 8-9: 5). As in pleurodires, centra are very strongly pinched (Fernandez and Fuente 1994) and the heavy diapophyses are triangular in dorsal view, occupying the middle of the centrum. Central articulations broaden slightly towards the rear of the series and anterior articulations are larger than rear articulations.

The third cervical (AMF127984, AMF127990) is opisthocoelous, and the circular central cotyle has paired intercentra at its base. The biconvex fourth cervical vertebra has a low, broad neural arch with zygapophyses widely separated. AMF68254, which was described by Lapparent de Broin and Molnar (2001) as resembling the fourth cervical of but with a lower neural spine, is here interpreted as the

30 fourth cervical of Spoochelys. The large postzygapophyses of AMF68254 are cojoined, and above them, a wide cavity is developed in the rear of the neural arch. Central condyles are rounded and dorsoventrally elongate; the anterior condyle has a notochordal dimple. Ventral keels of the fourth and fifth vertebrae are very deep, rounded in lateral view, with thick lower margins. The fifth vertebra LRF464 is procoelous, with small parapophyses on the lower edge of the anterior central cotyle.

The seventh cervical is biconcave (AMF127972, AMF127996 and LRFR465) with the anterior cotyle circular or squareish, and the posterior facet triangular, acute ventrally. The front facet bears very large parapophyses, which in LRFR465 for example, project forward of the centrum, buttressed by robust postparapophyseal laminae that extend back to the middle of the centrum. The neural arch is massive, elongated and broad and the ventral keel is reduced compared to that of preceding vertebrae. This biconcave seventh cervical, with its parapophyses projecting forward of the cotyle and triangular rear central facet is unique to Spoochelys.

In posterior cervicals of Spoochelys and Sunflashemys, bifurcation of the neural spine produces a triangular cavity that opens above the postzygapophyses. These cavities and the neural pedicle supporting the postzygapophyseal facets are another chelid-like feature.

The eighth cervical (AMF72276; LRFR466) is biconvex with a towering neural arch that is narrower than that of the seventh cervical. The rear condyle in AMF72276 is missing due to excavation damage, and the ventral keel is broken but was more strongly developed than in the seventh cervical. Postzygapophyseal facets are flat and not connected by a lamina, but are supported on a pedicle that extends well rear of the centrum.

A nuchal articulation is inferred for the eighth cervical of Otwayemys NMVP187261 (Gaffney et al. 1998; Hirayama et al. 2000). This cervical in Otwayemys is similar to that of Spoochelys, except that diapophyses are more strongly tilted, diapophysis and parapophysis are linked by a lamina, and a sharp midline crest extends along the neural arch (pers. obs.). In the eighth cervical of Otwayemys, structure of the ventral

31 keel, sloping dorsally in lateral view from a median projection below the centrum (as in AMF72276), strongly suggests that the seventh cervical of Otwayemys is biconcave, as in Spoochelys and Sunflashemys.

A paddle-like cervical rib is known for Opalania, but cervical ribs have not been recovered for Spoochelys. The parapophyses in Spoochelys are rather variable but are long and ossified in larger specimens, positioned further from the transverse processes than in Meiolania, extending below the centrum. Parapophyses are widely distributed among stem turtles and primitive cryptodires, actual cervical ribs are less common. Parapophyses and cervical ribs are unknown in pleurodires.

Cervical vertebrae of Ordosemys (Brinkman and Peng 1993), Dracochelys (Brinkman 2001) and Xinjiangchelys (Peng and Brinkman 1993) differ considerably from those of Spoochelys and Sunflashemys. In the Lightning Ridge specimens, the neural arch is set further back from the front of the centrum and is much taller; diapophyses are more robust, in the middle of the centrum and tilted; centra are more strongly pinched and more deeply keeled; parapophyses are much larger; and postzygapophyseal facets of the fourth and fifth cervicals face ventrally, not ventrolaterally as they do in Ordosemys. Moreover the central articulation pattern in Ordosemys appears to include an anterior biconcave centrum; and central articulations are very shallow in Xinjiangchelys.

It might be inferred from the fully roofed ‘armour-plated’ skull of Spoochelys that neck retraction was undeveloped, however all key features of the cervical series are chelid-like, indicating a predominantly lateral mode of neck movement. The articulation pattern is (2( (3( (4) )5) )6) )7( (8) and in Spoochelys the only variations from the chelid template are the biconvex fourth articulation and the presence of parapophyses. It is the fifth cervical that is biconvex in chelids. Small ‘inferolateral tuberosities’ in chelids from Early Cretaceous Patagonia (Lapparent de Broin and de la Fuente 2001) suggest that although parapophyses and cervical ribs are unknown in pleurodires, these structures were present in basal members.

Sacral and sacro-caudal vertebrae (Figs. 9, 12)

32 Articulated material is extremely limited and again, these elements in Spoochelys and Sunflashemys are so similar that separating the two taxa is difficult. Sacral centra of Spoochelys are short, flattened, wider and shallower than those of Sunflashemys. In sacrals and anterior caudals, the neural canal is broad and subtriangular, and the large transverse processes are flatter, more acuminate distally and set closer to the front of the centrum than in Sunflashemys. The processes are triangular in dorsal view and tilted at the diapophysis, so the transverse lamina is higher at the rear.

LRF407 is an articulated pygal and suprapygal. Two sacral vertebrae and one caudal vertebra are attached to the visceral surface, and the centrum of the last sacral is fused to the first caudal or sacro-caudal. The inconsistency of the sacro-caudal articulation is illustrated by a number of isolated specimens (AMF127978, LRF16, LRFR467, AMF6772, LRFR469, LRFR468 and AMF121638). This variable fusion is an important shared derived feature of Spoochelys, Sunflashemys and Meiolania. Morphological integration of sacral and caudal vertebrae is typical of pleurodires (Hoffstetter and Gasc 1969), seen also in Proterochersis and Notoemys zapatocaensis (Rueda and Gaffney 2003) in which transverse processes of the sacro- caudal contact the ilium. In the Lightning Ridge taxa, sacral and sacro-caudal transverse processes are also variably attached to the centrum, sometimes fused, sometimes apparently cartilaginous, sometimes very loosely sutured.

The anterior central facet of the sacro-caudal vertebra in Spoochelys is flat, very wide and aligned vertically. The posterior articulation is a well-developed circular cotyle, tilted anteroventrally as in Meiolania. Transverse processes are massive and were probably connected ligamentously to distal transverse processes of the last sacral vertebra, again as in Meiolania. Opisthocoely of the sacro-caudal or first caudal is another interesting similarity to Notoemys zapatocaensis (Rueda and Gaffney 2003).

The neural arch of the first ‘true’ caudal (or second caudal) of Spoochelys is wider than in the sacro-caudal vertebra (AMF121603 and LRFR470), and the centrum of this vertebra has a ventral midline crest and is opisthocoelous. The vast majority of turtle caudal vertebrae in the Lightning Ridge assemblages are opisthocoelous. Only

33 one biconvex specimen is known (LRF1229), from the rear of the series; and only one or two procoelous specimens have been cited (LRF733), from the distal end of the tail. It can therefore be stated with confidence that caudal vertebrae were opisthocoelous in both Spoochelys and Sunflashemys, and this is also the likely condition in Meiolania (contra Joyce 2007).

The Lightning Ridge assemblage includes numerous examples of ‘spoochelyid’ caudal vertebrae with strongly developed haemal keels and evidence of separate chevron bones. These were apparently prominent along the entire tail, probably from the second caudal back. Chevron bones are present in many specimens, resembling those of Meiolania rather than Proganochelys, being very broad in lateral view, elongate and curved posteroventrally, so the distal end is located posterior to the postzygapophyses.

While caudal ossifications are rather widely distributed among turtles, distal caudals of Proganochelys and Meiolania are uniquely enclosed in a bony tail club, and at least part of the caudal series is overlain by tail rings comprised of dermal ossicles (Gaffney 1985). Caudal osteoderms, rings or tail club attributable to the Lightning Ridge taxa have not been found, and until recently comparable structures were unknown in pleurodires. However, the extant Australian chelid Elusor macrurus Cann and Legler 1994 uniquely possesses a long, laterally compressed tail terminating in a ‘club’ comprised of shortened vertebrae capped by laterally expanded neural arches with a midline raphe or crest. The chevrons or haemal keels in Elusor (Cann 1998: 251) are broad in lateral view, very elongate and strongly curved posteroventrally, as in the Lightning Ridge taxa and Meiolania. In vertebrate groups that possess tail armour (such as stegosaurs), or that are tail swingers and tail scudders (sauropods, crocodylians), an opisthocoelous ball-and-socket joint occurs where strong axial movement opposes a fixed or rigid vertebra. In Spoochelys, the opisthocoelous articulation of the second caudal (or first ‘true’ caudal) vertebra, and massive transverse processes that indicate powerful dorsolateralis muscles, suggest a vigorous tail scudding or swinging function, if not caudal ossifications. In contrast, in Palaeochersis, despite the huge transverse processes, caudal osteoderms, rings or

34 sheaths are absent, and the chevrons are short elements, squareish in lateral view (Sterli et al. 2007: 33: 8D, E).

Pectoral girdle (Fig. 13) AMF66776, AMF66777, AMF127942 and AMF121587 are attributed to Spoochelys on similarities to Meiolania. This description is based on the latter specimen, with orientations following those for Proganochelys as proposed by Lee (1996). Missing the distal section, the scapular spine in AMF121587 is flexed medioventrally, as in Proganochelys and Palaeochersis (Sterli et al. 2007). The spine is rod-like, longer and narrower than the acromial process, and wide separation of the two processes, at about 120o as in Meiolania, indicates that the carapace was high-domed (Walker 1973). The glenoid is supported by a neck that is less developed than in Xinjiangchelys. The anterodorsal acromial margin forms a fine web of bone that is weakly sigmoidal in dorsal view and the acromial process is acuminate distally, as in Proganochelys. A less developed bony flange, rounded distally, extends ventrally along the acromial process, bifurcating near the glenoid. A third ridge of bone extends along the posterior surface of the acromial process, forming near the distal end, a sharp spur or prong directed posteriorly towards the coracoid. A similar acromial spike is present in Meiolania which has a huge semicircular or fan-shaped coracoid (pers. obs.). A photograph is published (Gaffney 1996: 22: 17) but these features have not been documented previously in Meiolania. Due to the three bony ridges, the acromial process of Spoochelys is markedly triradiate in section along its full length. The acromial process in Sunflashemys and Meiolania is subtriangular in section.

Humerus (Fig. 14) The humerus of Spoochelys (AMF68310, AMF(unreg.MH), AMF68321, AMF73508, AMF127956, LRF78 and AMF127940) is extremely robust as in Proganochelys, similar to Meiolania in the thickened but strongly reduced medial process of the proximal expansion. The humeral head is subspherical as in Meiolania, with a prominent shelf or shoulder, as in pleurodires (Gaffney et al. 2006). The lateral process extends proximally and the intertubercular fossa is shallow. The distal end of the humerus is blocky and the articular condyles are well-

35 formed, subspherical and directed ventrally. The ectepicondylar canal is closed and the ectepicondylar foramen opens just lateral to the capitellum (lateral condyle).

Ulna (Fig. 14) Two important features characterize the ulna of Spoochelys (AMF121621, AMF127944, AMF112769, LRF79, LRFR471 and LRFR472). The olecranon process rises high above the humeral articulation surface, creating a deeply curved sigmoid notch, unlike the flattish articular surface in advanced turtles (Gaffney 1990). This extended olecranon process is also present in Palaeochersis and Meiolania. The ulna is also notable for the heavy dorsal proximal ridge producing a deep dorsomedial trench on the shaft and a subtriangular proximal articular surface. This indicates tight cohesion with the radius, as in terrestrial turtles (Gaffney 1990), and strong development of this feature may be a meiolanoid synapomorphy.

Manus Turtle metacarpals in the Lightning Ridge assemblage are very short, with the proximal articular surfaces wider than total length of the element. Distal articulations are simple cylinders, and proximal acetabula of the phalanxes are deeply hemispherical with the ventral rim extending proximally so the articulation is strongly inclined. Overall morphology closely resembles Proganochelys and is consistent with a terrestrial lifestyle (Joyce 2004).

Pelvic girdle The acetabular section of the ilium of Spoochelys is extremely robust and blocky, and the dorsal section is perpendicular and may not expand laterally.

Femur (Fig. 15) Femora of Spoochelys and Sunflashemys are similar and specimens are assigned to Spoochelys on the basis of associated or semi-articulated material (LRFR452, LRF339). The proximal section of the femur in Spoochelys is notable because the trochanter major is laminate, merging continuously with the head into a broad flat surface. The head forms an arc greater than 180o in anterior and posterior views, and is strongly domed, curving dorsoventrally to the shaft. In Sunflashemys the head is

36 flatter, forms an arc of around 180o and is hooked or notched dorsoventrally. Projecting at an angle of around 60o from the rostrocaudal midline of the head, the trochanter minor is stout and robust. In Spoochelys, the trochanters are of equal height, situated more ventrally than in Proganochelys, connected by a weak crescent of bone. The intertrochanteric fossa is relatively shallow and unconstricted. There are similarities to primitive eucryptodires, but in all the above features, there are clear resemblances to chelid pleurodires (pers. obs.). In contrast however, the distal articular condyles are strongly differentiated. The distal view is rectangular, deeply notched at the intercondylar fossa. The fibular articulation is smaller than the tibial condyle which develops a slight flange that extends dorsally along the anterior surface of the shaft. A pronounced triangular facet of uncertain function is indented into the posterior surface of the fibular condyle, a feature also present in Sunflashemys.

Tibia (Fig. 15) This description is based on AMF1227958, a complete specimen resembling the tibia of Proganochelys in overall proportions. The massive proximal expansion comprises half the total length of the element and is three times wider than the narrowest width of the shaft. The proximal extreme is remarkable for the wide shallow concavity on the dorsal surface and the domed protuberance on the medial margin of the shaft – pleurodire-like features that are also present in Notoemys (Fernandez and de la Fuente 1994) and chelids (pers. obs.). In all tibiae specimens, the medial dome of the distal articulation is hypertrophied, suggesting tight cohesion with the astragalus. In distal view, the distal articulation is oval in Spoochelys, but it is subtriangular in Sunflashemys.

Tarsus and pes (Fig. 16) Manus and pes are very similar in Spoochelys and Sunflashemys and until further material comes to light, this description applies to both taxa and is based on small assemblages of tarsal material and isolated elements from several sites. In AMF127961, the astragalocalcaneum is fused indistinguishably as in most adult cryptodires and Meiolania, and tibial and fibular articulation surfaces join to form a ridge. The astragalus is expanded posteromedially and the ventromedial area is

37 hugely swollen and hemispherical, as in plantigrade turtles. Metatarsal V, preserved in AMF127961, is a large blocky unit resembling that element in Notoemys, Araripemys and . Metatarsals are similar to Proganochelys, broadening proximally. In metatarsals II, III and IV pronounced overlap facets are developed as ventrolaterally projecting tubercles, a distinctive feature also occurring in Meiolania (Gaffney: 63: 52; and pers. obs.) and Palaeochersis (Sterli et al. 2006), but not Proganochelys. Distal metatarsal articulations are cylindrical and undivided, a primitive feature, and proximal acetabula of phalanges are circular with the ventral rim extended. A small, weakly recurved generalized ungual resembling the unguals of chelids is included in holotype material for Sunflashemys, and unguals of Spoochelys are probably similar. Phalangeal formula is likely 2222?

Discussion The skull of Spoochelys was high, fully roofed and probably spiney along the temporal margin. The neck was short, flexion was predominantly lateral, and it is possible that the head could be concealed, at least partially, below the extended carapace front which was reinforced by bony domes. The tail was broad and long, and caudal osteology suggests a capacity for swinging or scudding movements and possibly small ossifications (Fig. 6).

Spoochelys shares numerous derived features with the meiolaniids. The heavy dermatocranial scutes, arranged in the synapomorphic meiolaniid pattern, may have developed into lumps and bosses in older animals. A wide bracket-shaped step, the interpterygoid vacuity (‘intrapterygoid slit’ in Tertiary meiolaniids), separates basisphenoid and pterygoid; and the epipterygoid is large and distinctive. Both groups share unique postcranial features – an acromial spike, a triangular proximal ulnar articulation, tubercular overlap facets of metacarpals and metarsals, among other derived features.

The high-domed carapace and podial structure indicate that Spoochelys was a terrestrial turtle, as were Meiolania, and Proterochersis (Gaffney et al. 2006). In cranial progressions Spoochelys resembles Notoemys laticentralis, the only pre- Cretaceous pleurodire preserving skull features. As in Notoemys, Spoochelys has a

38 massively broad basisphenoid and full ventral exposure of the prootic. Inner and middle ear regions and recessus scalae tympani are unfloored, and the facial nerve is separated from the canalis cavernosus, opening into the cavum acustico-jugulare.

The unique mix of archaic and apomorphic states suggests phylogenetic affinity with australochelyids and Proterochersis – and some workers contend that Palaeochersis is a pre- or proto- pleurodiran (Lapparent de Broin 2000; Lapparent de Broin et al. 2004), although this is contested (Joyce 2007; Sterli and Joyce 2007; Sterli et al. 2007; Sterli 2008; Gaffney et al. 2006; Gaffney et al. 2007).

Despite the fact that 25:125 derived character states are shared by the Lightning Ridge taxa and platychelyids, results of a PAUP analysis (Chapter Nine) imply that a number of key ‘pleurodire-like’ features in the meiolanoids are independently developed in the Pleurodira. This outcome, probably skewed by the large amount of missing data, is similar to results obtained by Dryden (1988), Joyce (2007) and others, which infer that pleurodiran features are reversals of cryptodiran derivations. Oddly enough, the situation recalls the century-old argument concerning the pleurodiran versus cryptodiran status of the Meiolaniidae (Boulenger 1887, 1889; Woodward 1901; Baur 1889). Debate on meiolaniid relationships is ongoing and is unlikely to be resolved by this present study.

Essentially, Spoochelys is a primitive terrestrial turtle retaining the postparietal, supratemporal and anterior supramarginal scales, features otherwise identified only in Triassic groups. The skull is ‘armour-plated’ with ossified dermal scutes arranged in the pattern that is synapomorphic for meiolaniids, and the basicranium exhibits a wide bracket-shaped interpterygoid vacuity. Features diagnosing the family Meiolaniidae as defined by Gaffney (1996) are absent, nonetheless, a sister-group relationship with the meiolaniids is soundly substantiated by a suite of shared derivations of the temporal roof, epipterygoid, basicranium, lower jaw and axial, appendicular and podial skeleton. A limited quota of derivations suggests that Spoochelys and by inference the meiolaniids share a more recent common ancestry with basal pleurodires than with cryptodires.

39

CHAPTER THREE

SUNFLASHEMYS BARTONDRACKETTII N. GEN., N. SP. (MEIOLANOIDEA: SPOOCHELYIDAE), A PRIMITIVE SWAMP TURTLE FROM THE OPAL FIELDS OF LIGHTNING RIDGE, NEW SOUTH WALES, AUSTRALIA

Sunflashemys bartondrackettii, n. gen., n. sp., a primitive semi-aquatic turtle from Lightning Ridge, New South Wales, is sister taxon to Spoochelys, from the same location. Sunflashemys is distinguished by derived features and a unique combination of archaic structures otherwise lost, reduced or transformed in other turtles.

The holotype of Sunflashemys was discovered in 2001 by opal miner Peter Barton and his son Brett at Tyrone’s Field on the Coocoran, west of Lightning Ridge. At a depth of about 12 metres in the Finch Claystone horizon, the Bartons encountered opalised bone representing a single small turtle. The skeleton was apparently scattered over several square metres of the biofacies, and many bones were processed through mining machinery. Fortunately, the Bartons managed to collect the braincase, a humerus and carapace fragments direct from the mine face. The biofacies was then partly excavated and searched by the author. No further bone material was found in situ, however opal-dirt from the floor of the drive was brought to the surface, washed and sieved, resulting in retrieval of smaller bones and multiple broken shards.

Many vertebrate locations at Lightning Ridge, particularly the fossil-rich Coocoran fields, carry a diversity of forms, more than one turtle taxon, and more than one individual turtle. Serendipitously, Sunflashemys was the only vertebrate represented in this section of biofacies at the Tyrone’s site. However, carapace, plastron, pelvis, femora, distal podials and caudal vertebrae were scrappy or missing, presumably excavated and lost during the mining process. This has created problems with assessment and identification of isolated examples of these elements from other locations. Material referred to Sunflashemys is that which is closely comparable, or is extrapolated to be closely comparable, to material collected at the Tyrone’s site.

55 Some assignments are based on deduction and inference rather than direct evidence. It is highly likely that certain attributions will be revised in future, given the fragmentary nature of the specimens and apparent subtlety of differences between Spoochelys and Sunflashemys, particularly in axial and podial elements.

Type material of Sunflashemys is preserved as glass-like transparent opal. Sutures and foramina of the ventral basicranium are recorded in great precision (Fig. 17), and intricacies of the middle and inner ear are microscopically detailed. A minute stapedial foramen and canal are preserved inside the columella. This veracity of replication suggests that the turtle was aestivating in soft mud when it died; or slow burial in very fine silica-rich sediments and calm conditions after deposition. The site also produced a few scraps of unworn plant detritus, pine twigs and small crayfish gastroliths, but there was a peculiar absence of larger plant fragments and molluscs. Peter Barton also recovered the sacral vertebra of a mammal (Fig. 68) and a turtle caudal vertebra assigned to Spoochelys from the ‘second level’ at about 25 metres, a deeper opal-bearing horizon at the same site.

The paratype braincase of Sunflashemys (Fig. 18) was discovered in 2007 at Emu’s Field on the Coocoran, by opal miners Peter Drackett and Stefan Benaud. Significant features of the ventral basicranium that are missing in the type are beautifully preserved in this second specimen, providing important information on structure of the facial nerve and anterior section of the basisphenoid.

In the following description and discussion, comparisons are made across many Mesozoic forms and references are essentially as for the previous chapter. Again, texts on cranial and postcranial features of primitive pleurodires are crucial (Burbridge et al. 1975; Fernandez and Fuente 1994; Meylan 1996; Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001; de la Fuente 2003; Rueda and Gaffney 2005; Gaffney et al. 2006).

56 SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996 Family SPOOCHELYIDAE n.

Sunflashemys n. gen. Diagnosis. As for only known species. Etymology. ‘Sunflash’ - opal-miners’ term for the type of opal in which the Tyrone’s material is preserved; ‘’ - turtle.

Sunflashemys bartondrackettii n. gen., n. sp. Type specimen. Australian Museum, Sydney, AMF116217, a partial skeleton. Includes braincase and fragments of lower jaw and hyoid; carapace (first costals, first neural, peripherals three to ?seven, pygal fragment and plastron shards); partial cervical and thoracic vertebrae; fragments of appendicular girdles, humerus, podials, manus and pes.

Locality and horizon. Tyrone’s Field on the Coocoran opal fields west of Lightning Ridge (Appendix 2.0.4).

Paratype specimen. A partial skull from Olga’s Field, Coocoran, held at the Australian Opal Centre, Lightning Ridge, pending donation to that institution under the Australian Commonwealth Government’s Cultural Gifts Program.

Formation and age: Finch Claystone facies of the Wallangulla Sandstone Member, Griman Creek Formation. Early - middle Albian (Exon and Senior 1976; Morgan 1984; Burger 1986, 1995); middle-late Albian (Dettman et al. 1992).

Etymology. ‘bartondrackettii’ for Peter and Brett Barton; and Peter and Vicki Drackett. The type material was generously donated to the Australian Museum, Sydney, under the Cultural Gifts Program.

Diagnosis: A primitive turtle distinguished by: posteroventral surface of basisphenoid and ventromedial section of prootic cartilaginous; basisphenoid very large with

57 posterior median tubercle or crista; foramen caroticum basisphenoidale = foramen posterius canalis carotici interni and external carotid artery unfloored; indented posterolateral ‘wings’ of pterygoid; foramen nervi facialis in basisphenoid-pterygoid suture; canalis nervi facialis elongate, floored by pterygoid and roofed by prootic, separated from canalis cavernosus; canalis cavernosus large and bean-shaped in section, lying ventral to fenestra ovalis; cavum labyrinthicum, cavum acustico- jugulare and recessus scalae tympani without bony floor as in Spoochelys and Notoemys; basioccipital hypertrophied and elongate, prominent basioccipital tubercles ventrally curved, aligned rostrocaudally and projecting rear of foramen magnum, with posterolateral buttresses; very large stapes, stapedial footplate and fenestra ovalis. Sulcus between first and second vertebral on rear portion of first costal, first costal narrow rostrocaudally, shallow carapace scute sulci; neural plates sutured neuro-centrally to anterior thoracic vertebrae; first and second thoracic vertebrae retain postzygapophyseal section of neural arch; large Rathke’s gland cavities and medial musk duct openings in bridge peripherals.

Referred specimens. Cranial elements: quadrate AMF121643; cervical vertebrae: three AMF105649; four AMF112750, LRF15; five AMF121639; six AMF68301, AMF127971; seven AMF68245, AMF127982, AMF127990, AMF68306, AMF121637, AMF127982, AMF127999; AMF127999; cervical fragments AMF121630, AMF121631, AMF121632, AMF121633, AMF121608; thoracic vertebrae: AMF121604, AMF121593; sacrum, sacrals and sacro-caudal: LRF274, AMF68276, AMF127994, AMF127973, LRF473; caudal vertebrae: AMF127999, AMF121606, AMF127993, AMF121605, AMF121644, AMF121635, AMF121636, AMF127997, AMF127995, AMF121645, AMF127989, AMF127974; peripherals: AMF128011; femur: LRF46, AMF112754; ungual: AMF127968.

Description and comparison Skull (Figs. 17, 18, 19) The type skull AMF116217 consists only of the braincase, with cavum cranii, basicranium, otic capsules and occiput, and fragments of hyoid and lower jaw. Apart from a midline section of the parietal, the temporal roof is missing. Preservation varies from indecipherable (dorsal section, and front part of basisphenoid) to extremely fine (ventral structures). Post-mortem compaction has distorted the dorsal

58 surfaces of the otic chambers, and extremities were severely flaked and chipped during excavation. Incomplete bone contacts around the large foramen stapedio temporale suggest that this specimen represents a juvenile or immature adult - estimated total length ~ 400 mms.

The paratype braincase is 50% larger than the type specimen, comprising basicranium, braincase and partial otic chambers. Claystone matrix fills the cavum crania, and dorsal sutures are obscured by dessication cracks that were secondarily cemented with silica during diagenesis. The specimen was severely abraded by mining machinery and is broken transversely at the front of the basisphenoid rostrum. Epipterygoids, outer ear structures and margins of the foramen magnum are lost, however basicranial bones are precisely preserved in translucent common opal. The specimen is additionally interesting because the basisphenoid and basioccipital are slightly twisted around the axial midline. This apparently pathological condition has caused asymmetric development of primary neurocranial elements, so that on the left side, the basisphenoid and basioccipital tubercle are enlarged and the pterygoid- basisphenoid contact is compacted. This left pterygoid section closely resembles the area of posterolateral contact between the pterygoid and basisphenoid in the basicranium of Spoochelys.

In both skull specimens of Sunflashemys, the basisphenoid and prootic exhibit an irregular, deeply ‘wrinkled’ surface texture, a peculiar effect indicating that these elements remained unossified for an extended period during the life of these turtles. In this regard, Sunflashemys resembles the meiolaniid cf. Warkalania from Riversleigh which exhibits a number of cartilaginous and unsutured contacts (Chapter Five). A cartilaginous inner ear region is considered to be typical of pleurodires. General dimensions, topology and morphology of the canalis cavernosus and inner and middle ear in Sunflashemys conform very closely with Meiolania.

Parietal In AMF116217, only the medial part of the parietal remains, however the thickness of broken edges indicates that temporal emargination was minimal or undeveloped. The surface is decorated with small rippled grooves that are aligned rostrocaudally,

59 but it is unclear if this is scute or bone texture. A short suture with the epipterygoid above the foramen nervi trigemini is discernible.

Quadrate This description is based on type and paratype specimens, and AMF121643, an isolated partial quadrate. In the skull specimens, most of the quadrate on both sides is missing and sutures are fused or imprecise. Quadrate margins on the front of the otic chamber are obscure, but presumably the quadrate reaches laterally and dorsally to contact prootic and opisthotic respectively. The quadrate forms the posterolateral roof, and the posteroventral floor, of the canalis cavernosus which is a wide horizontal channel, bean-shaped in section, lying level with the base of stapes, suggesting that the lateral head vein was positioned ventrally. In the paratype, as a result of premortem distortion, the left canalis cavernosus is situated more dorsally, but is still below the level of the floor of the cavum labyrinthicum. The quadrate forms the lateral margin of the aditus canalis stapedio-temporale. As in Proganochelys, the incisura columellae auris is lateral to the suture with the pterygoid and judging by the size of the canals, stapedial artery and lateral head vein were very large. The cavum tympani is only moderately developed and the antrum postoticum was probably small. Enclosing both stapes and eustachian tube, the incisura columellar auris is open posteroventrally, and the quadrate curves posteroventrally around the incisura.

Epipterygoid The right epipterygoid is preserved in the type skull, a supersize triangular element, broad at the base, closely resembling that of Spoochelys and Meiolania. It reaches a short contact with the parietal dorsally, forms the anterior and lower margin of the foramen nervi trigemini, the rear margin of the fossa infraorbitale and extends below the level of the basisphenoid anteriorly. A short posterodorsal contact with the prootic is partly obscured by compaction damage. The very long suture with the quadrate at the front of the otic chamber runs posteroventrally from the lateral margin of the trigeminal foramen, with no evidence in either specimen of a fossa cartilaginous epipterygoidei.

60 Ventrally the epipterygoid-pterygoid suture is horizontal, very low on the front of the braincase, so the epipterygoid forms most of the lateral wall of the canalis cavernosus. Contact between the basisphenoid rostrum and the anterior tip of the epipterygoid is discernible in type and paratype specimens, and also in Spoochelys. Not previously reported in turtles, epipterygoid-basisphenoid contact is reminiscent of the condition in primitive reptiles, in which the epipterygoid contributes to the palatobasal articulation, carrying the basipterygoid process from the braincase (Romer 1956). The condition in Sunflashemys differs from that of parieasaurs, in which the epipterygoid has a narrow ascending process and cartilaginous ventral attachments; and from captorhinids, in which a deep ventral process of the epipterygoid sits ‘in a pocket of the pterygoid’ forming the primary basicranial articulation (Gaffney 1983).

Pterygoid The front section of the basicranium and palatal sections of the pterygoid are not preserved in either skull specimen, hence presence or otherwise of a processus trochlearis pterygoidei cannot be determined. Ventrally, the pterygoids extend posterolaterally as ‘wings’ with trough-like concavities, widely separated from the basioccipital. The basipterygoid contact is unfused, the suture deeply convoluted and short, leaving the posterolateral edge of the basisphenoid free, as in Spoochelys and Notoemys.

The primitive state of the basicranium, resembling Heckerochelys and Condorchelys, indicates that an interpterygoid vacuity was present. In the paratype specimen, the ventral pterygoid lamina that forms the floor of the interpterygoid opening has sheared away, and the pterygoid margins of the vacuity are indicated by deep blocks of bone at the edge of the basipterygoid articulation on each side.

Asymmetry of the pterygoids in the paratype skull is pathological and the left pterygoid is similar to the pterygoids in Spoochelys. This description relies on the incomplete pterygoids in the type skull and the more complete right pterygoid in the paratype. As in Notoemys and Spoochelys, the external carotid artery was unenclosed and traversed the lower surface of the basisphenoid in broad grooves extending back from the foramen caroticum basisphenoidale. A second possible scenario is that a

61 small section of the carotid artery was floored by the pterygoid and roofed by the basisphenoid and prootic, with the foramen posterius canalis carotici interni entering between the pterygoid and prootic. This seems very unlikely however, given the strong development of the posterior basisphenoid grooves.

In Sunflashemys, the pterygoid forms the anteromedial floor of the canalis cavernosus below the level of the basisphenoid and is widely separated from the rear section of the basisphenoid, the cavum labyrinthicum and basioccipital. The foramen nervi facialis is a small opening in the pterygoid-basisphenoid suture. The paratype specimen shows unequivocally that posterolateral to the foramen nervi facialis, the pterygoid floors an elongated posterior section of the facial nerve, carrying the nerve into the medial roof of the canalis cavernosus, separating it from that chamber. The canalis nervi facialis is roofed by the prootic and opens from the lower surface of the prootic into the cavum acustico-jugulare. The condition resembles not only the chelid pleurodires and (Gaffney 1979: 131: 40) but also Notoemys, in which ‘the foramen of the hyomandibular branch of the facial nerve (VII) [is] located in the prootic wall between the canalis cavernosum and cavum labyrinthicum’ (Marcelo de la Fuente persn. commun.). Subdivision of the facial nerve within its own canal, separate from the canalis cavernosus, is a key pleurodiran synapomorphy (Gaffney 1975, 1979; Gaffney et al. 1991; Gaffney and Meylan 1998; Gaffney et al. 2006). In Heckerochelys (Sukhanov 2006) and Kayentachelys (Gaffney et al. 1978; Sterli and Joyce 2007), the foramen nervi facialis opens from the anteroventral face of the prootic and there is no posterior bony enclosure.

In Sunflashemys, the right pterygoid sheet that underlies the canalis nervi facialis is not sutured to the overlying basisphenoid and prootic. This morphology is consistent with that of Tertiary meiolaniids, including the meiolaniid cf Warkalania from Riversleigh (Chapter Five), in which the posteromedial extension of the pterygoid is separated from adjacent elements by an open fissure that was probably cartilaginous in life (Gaffney 1983).

Exoccipital The exoccipital contributes to the lower margin of the foramen magnum, but is undeveloped, widely separated from the processus interfenestralis and does not

62 contribute to the occipital condyle. Position of the exoccipital-opisthotic suture on the outer braincase wall is indeterminate. The suture with the basioccipital runs dorsal to the basioccipital tubercles and the exoccipital forms the posterior wall of the foramen jugulare anterius, as a heavy ventromedial process bracing the rear section of the basioccipital, bounding the dorsomedial part of the cavum acustico-jugulare. There is no foramen jugulare posterius.

The posterior walls of the exoccipitals form a concave vertical surface. In the paratype, a large single hypoglossal foramina opens on each side, high above the basioccipital tubercles, and a second smaller foramen pierces the lower margin of the buttress of bone that forms the posterodorsal wall of the recessus scalae tympani. These foramina open downwards and are visible only from below, as in the meiolaniid cf. Warkalania, in contrast to Meiolania, in which the foramina open rearwards. In the type specimen, there are two hypoglossal foramina on each side, also opening ventrally; and a lamina of dessicated skin is preserved over the left exoccipital, concealing the hypoglossal nerve foramina on that side.

Basioccipital The basioccipital is blocky and massively thick, the smooth surface in both specimens indicating that it was fully ossified, unlike the basisphenoid and prootic. Basioccipital contacts are with the basisphenoid anteroventrally, the opisthotic anterodorsally and exoccipital posterodorsally. The rear section of the ventral wall of the cavum labyrinthicum and the medial wall of the recessus scalae tympani are formed by the basioccipital. As in Spoochelys and primitive pleurodires such as Notoemys and Araripemys, the recessus is conspicuously unfloored.

The basioccipital tubera are strongly developed and aligned parasagittally, larger and longer than in Spoochelys, Meiolania and Notoemys, with lateral projections or buttresses that extend dorsally, creating the posterior wall of the recessus scalae tympani. Posteriorly the tubera are constricted into crests that are connected by a web of bone, curved anteriorly, across the base of the basioccipital condyle. The crests continue as fine laminae onto the neck of the condyle. The condyle is large and hemispherical, indicating that the atlantal centrum may have been concave anteriorly, although the rounded form may be the result of post-excavation abrasion. The

63 paratype specimen has a subsidiary basioccipital tubercle in the same anteromedial position as the small tubercle in the meiolaniid cf. Warkalania from Riversleigh (Chapter Five); this tubercle is not duplicated on the right side, perhaps due to pathology, and is absent in the type skull.

In the floor of the cavum cranii, the type specimen has a stepped ventral separation of the basioccipital from the posterior margin of the basisphenoid, similar to the structure in Proganochelys and Meiolania.

Prootic In ventral view, the prootic is strongly exposed, finishing dorsal to the basisphenoid. In the type skull, the prootic is globular and the basisphenoid-prootic contact does not appear to be sutured. This dorsal position of the prootic, also present in the paratype, is more primitive than Notoemys, in which the prootic is apparently on the same ventral plane as the base of the basisphenoid and is grooved to accommodate the carotid artery.

In the paratype, both prootics are strangely contracted and shrivelled in appearance. Clearly though, the prootic is heavily expanded ventrolateral to the fenestra ovalis as in Notoemys, with an extensive contact with the quadrate in the roof of the canalis cavernosus, a feature shared with Notoemys (Marcelo de la Fuente persn. commun.), Meiolania and Crossochelys (Simpson 1938: 225: 3B). The prootic-quadrate contact dorsal to the canalis cavernosus is small in cryptodires (Gaffney 1979; Gaffney: 1990: 57: 46C).

Although the cavum labyrinthicum is unfloored, the prootic contacts and partly underlies the lateral edge of the base of the processus interfenestralis of the opisthotic. The prootic forms the medial margin of the aditus canalis stapedio- temporale, and probably the anterior edge of the foramen stapedio-temporale. As in Spoochelys and Meiolania, the prootic makes up the entire posterior margin of the foramen nervi trigemini; and there is no anterior prominence or projection that might be construed as a processus trochlearis oticum.

64 Opisthotic Dorsally, the opisthotic forms the rear half of the otic chamber, approaches the rear of the cavum tympani and probably contributes to the dorsal section of the foramen magnum. In the type skull, sutures are squamous and complex around the large foramen stapedio-temporale and partly overlain by the supraocccipital, but it appears that the opisthotic reaches the posterior margin of that foramen, as in Meiolania.

Ventrally the opisthotic-quadrate suture crosses the inflated ceiling of the cavum acustico-jugulare and the opisthotic reaches the prootic at the dorsomedial wall of the aditus canalis stapedio-temporalis. The opisthotic-exoccipital contact is a straight suture diagonally traversing the roof of the recessus scalae tympani, continuing into the foramen jugulare anterius. A brief opisthotic-basioccipital contact closes the large fenestra perilymphatica, between the hiatus acusticus and foramen jugulare anterius. The processus interfenestralis is proportionally larger than in the Tertiary meiolaniids, and the swollen distal end is fully visible from below, contacting the prootic and basioccipital.

The opisthotic-prootic suture lies in the roof of the cavum acustico-jugulare and the opisthotic reaches the margin of the aditus canalis stapedio-temporale but does not appear to form the lower section of the canalis stapedio-temporale, as it does in Meiolania.

Basisphenoid The basisphenoid is a massive element, broadly exposed on the basicranium, extending well posterior to the pterygoid. There is a median tubercle or crest, and posterior to this the basisphenoid divides into two uneven ridges that partly underlie the basioccipital. Spoochelys, Notoemys and chelids also have this weakly W-shaped basisphenoid-basioccipital junction. As in Spoochelys, the long posterolateral margin of the basisphenoid forms the medial edge of the open cavum labyrinthicum. Partly concealing the inner ear in ventral view, the margin is formed by curved cantilevers or shelves dorsal to the ventral surface of the basicranium.

65 The basipterygoid suture is unfused and heavily convoluted. The paired foramen caroticum basisphenoidale are positioned at the posterior limit of the rostrum basisphenoidale, just rear of the basipterygoid processes. The internal carotid canals are tiny, running anterodorsally within the basisphenoid, lateral to the rostrum basisphenodale on each side. The transverse break at the front of the paratype specimen reveals that the bone is very shallow above the paired carotid canals, which lie close together in the floor of the sella turcica (Fig. 18C). The foramen anterius canalis caroticus interni (facci) would therefore open from above the rostrum basisphenoidale and the trabeculae as in Meiolania.

Grooves extending posterolaterally from the foramen caroticum basisphenoidale represent the roof of the external carotid artery. A small section of that roof may be formed by the pterygoid but essentially, the external carotid artery was unfloored. The unenclosed division between carotid and palatine arteries was posterior to the basipterygoid processes, which diverted the forward passage of both vessels – the canalis caroticus internus inside the basisphenoid passed dorsal to the basipterygoid processes and the basisphenoid rostrum. The foramen posterius canalis carotici laterale appears to be located adjacent to the basisphenoid processes, so the palatine artery was partly enclosed in bone lateral to the basisphenoid rostrum. In Sunflashemys (and in Chubutemys; Fig. 40) the forward path of these soft tissue structures is deflected at the posterolateral limit of the basisphenoid rostrum. This is rather different from the condition in Heckerochelys (Sukhanov 2006) and Mesochelys (Evans and Kemp 1975) in which the carotid artery enters the basisphenoid and the palatine artery enters the basipterygoid articulation anterior to the basipterygoid process. A basipterygoid process is widely distributed among primitive cryptodires and considered plesiomorphic (Rieppel 1980; Brinkman and Wu 1999). Details are undocumented and presumably unknown for Kayentachelys (Sterli and Joyce 2007). Palatine artery structure in Sunflashemys is not homologous with that of Mongolochelys, Kallokibotion and basal eucryptodires, in which the interpterygoid vacuity is lost and the fpccl pierces the suture between basisphenoid and pterygoid, forward of the basipterygoid processes near the front of the rostrum basisphenoidale.

66 As shown in the paratype (Fig. 18C), the dorsum sellae is very high and wide and the foramina nervi abducentis are located ventrolaterally. The dorsum sellae is subdivided into two deeply concave chambers by a thin sagittal crest of bone that meets the sella turcica above the rostrum basisphenoidale. In Meiolania this division is parasagittal, producing a concavity on the midline above the paired foramen anterius canalis carotici interni which open just dorsal to the front of the rostrum basisphenoidale.

Columella auris In the type skull, post-mortem distortion has dislodged the right stapes, so the footplate is resting inside the cavum labyrinthicum against the hiatus acusticus. The left stapes is preserved in place, the shaft bridging the ventral portion of the cavum acustico-jugulare. The relative distance between the neurocranim and the incisura columellae auris is greater than in Meiolania and resembles Notoemys. The stapes is comparable in size to that of Palaeochersis (Rougier et al. 1995) although proportionally smaller in the paratype skull. Fully exposed in ventral view, the footplate is strongly expanded and the fenestra ovalis is correspondingly large. The footplate contacts the prootic anteriorly and the base of the processus interfenestralis posteriorly. In lateral view the footplate cone is faintly subtriangular, longer rostrocaudally than dorsoventrally, wider at the front. The cone base is aligned vertically and the posterior cone margin turns outwards slightly. The columellar shaft is faintly curved dorsally, lies horizontally and is inflected posteriorly at an angle of about 100o to the midline axis of the skull. Under high magnification, internal microstructure is visible. The stapedial foramen is in the anterior surface of the shaft, about one third of the distance between footplate and incisura and the stapedial canal leads medially. A cone-shaped webbed structure can be seen inside the footplate. These features, not observed previously in fossil turtles, may provide information on evolution of the hearing mechanism.

Lower jaw Partial articular condyles from the left and right jaw rami were retrieved with the type material. The dentary reaches ventral to the prominent foramen nervi auriculotemporalis, but the surangular is large, the primitive condition. Presence or absence of a splenial cannot be ascertained due to breakage and the bones making up

67 the area articularis mandibularis are fused indistinguishably. The area articularis mandibularis is faintly dished and weakly saddle-shaped or divided. The overall similarity to chelid morphology (Elseya, for example) is very striking.

Hyoid Oval to circular in cross section and rather slender, the proximal sections of two cornu branchiales (hyoid horns) resemble the anterior section of the branchiale element preserved in Spoochelys. These are presumably the ceratobranchialia anteriora (after Schumacher 1973).

Carapace (Fig. 20) Scutes Broad vertebral scutes are indicated by sulci on the first costal. The first vertebral appears to be bowl- or mushroom- shaped and the posterior margin seen on the first neural is curved anteriorly. The sulcus between the first and second vertebral is close to the posterior margin of the first costals.

On the peripherals, scute sulci are wide, shallow and poorly defined. As in Notoemys, dorsal surfaces of peripherals four to eight show the junction of two pleural sulci meeting the marginal sulcus which is apparently confined to the peripherals and does not extend onto the costals. On the lateral face of the peripherals, the marginal sulcus is wide and shallow.

Costals, neurals and anterior thoracic vertebrae (Figs. 20, 21) Sparse and badly broken carapace elements from Tyrone’s suggest a relatively high- domed shell, with narrow bridge peripherals widening posteriorly into a shelf that is slightly upturned at the edges. Anterior neurals, costals and thoracic vertebrae from Tyrone’s allow reconstruction of a portion of the anterior carapace. Plastron fragments from the type location are indecipherably smashed.

First costals are rather small and short rostrocaudally, laterally acuminate, with curved anterior margins. The bone is thick at the front (thicker than in the first costals of Spoochelys) but is very thin posteriorly. The first thoracic rib is very long, extending to the adjacent peripheral. The rib does not form a deep blade-like arc as in

68 Spoochelys, Chelycarapookus and Meiolania but as in these forms, strong transverse sutures anteromedially represent the contact surface for the scapula process.

As preserved, the first neural is a large subrectangular element that may have been more drum-shaped originally. The front section is robust and curved convex anteriorly, but the posterolateral edges are strangely thin and broken. A rounded midline crest is developed and is continued in a narrow fragment that perhaps represents part of the second neural. This second element is also extremely thin laterally. Together these two neurals indicate an irregular neural series.

A badly damaged first thoracic vertebra and fragmentary second thoracic were retrieved from the Tyrone’s site. AMF121604 and AMF121593 are second thoracic vertebrae from other locations. Compared to the cervical vertebrae, anterior thoracic vertebrae in Sunflashemys are very large and elongated. In the type material, the centrum of the first thoracic is twice the length of the sixth cervical. Thoracic centra are hour-glass shaped in ventral view, with a slightly-rounded V-shape ventrally, the angle becoming shallower in the posterior series, and the ventral margin is straight as in Pleurodira (Hoffstetter and Gasc 1969; pers. obs.). The form is distinctive, differing from Proganochelys in which the keel widens between central articulations; from platychelyids in which the ventral surface is flattened; and from Meiolania in which the thoracics are roughly U-shaped in section (Gaffney 1996). The closest similarity appears to be with Proterochersis (Fraas 1913).

In the fragmentary first thoracic (AMF116217), most of the neural arch is missing, so structure of the prezygapophyses is unclear. Facing anteriorly, the front central facet is triangular and platycoelus or weakly concave. As in Proganochelys, the morphology suggests limited mobility between the eighth cervical vertebra and the first thoracic vertebra. Ribheads were very loosely attached, not sutured to the thoracic vertebrae. In the second thoracic vertebra (AMF116217), the centrum and neural arch extend posterior to the second ribhead articulation and a large postzygapophyseal arch is retained, with oval tubercles that appear to be reduced postzygapophyses. Postzygapophyses are also present in referred specimens AMF121604 and AMF121593. AMF121593 is a partial neural with the top sections of neural canal and ribhead facets. AMF121604 is a complete vertebra with neural

69 plate and a postzygapophyseal arch but without the postzygapophyseal nodules that are present in the first thoracic. This condition seems to be unprecedented - no record can be found in the literature of persistence of the neural postzygapophyseal arch in the thoracic vertebrae of turtles.

In the anterior thoracics at least, neural bones are sutured to the vertebrae midway between the neural arch and the centrum, the suture dividing the large ribhead facets in half. The costo-vertebral tunnel is very constricted in Sunflashemys, because the neural plate is very close to the neural canal and the diapophysis. In both AMF121604 and AMF121593, the neural ‘bone’ is indistinguishably fused to the spinal arch. AMF121604 in particular seems to demonstrate that the neural ‘bone’ is not a separate ossification but is formed by expansion and fusion of the prezygapophyses and the neural spine. The prezygapophyseal section slightly overlaps the spinal shield section and the two flattish plates are delineated by a transverse sulcus with a midline ‘spike’ suggesting the posterior midline division between each prezygapophysis. At present it is unclear if this morphology persists throughout the thoracic series in Sunflashemys and perhaps the condition is ontogenic. An alternative explanation might be that the transverse dorsal sulcus is the suture between two neural bones that are arranged in the usual manner, that is, the suture between the rear section of the preceding neural and the front section of the following. However, AMF121604 is a transparent specimen, internal histology is visible and the transverse incision is definitely not a suture. In fact, it also appears to represent the sulcus between first and second vertebral scutes.

Usually in turtles, the neural-thoracic correlation is disjunct because two neural bones ‘overlap’ each vertebra, the ribheads attach between the vertebrae, the postzygapophyseal sections of the neural arch are obliterated and the neural blade is a deep continuous sheet along the carapace roof. This may well be the structure towards the rear of the carapace in Sunflashemys, but morphology of the anterior section seems unique and extremely archaic.

Peripherals (Fig. 20) Left peripherals ?three to ?seven are partially preserved and lack the bulging supramarginal scales seen in Spoochelys. In Sunflashemys, bridge peripherals are

70 narrow dorsally and elongated, however the shape of the lateral surfaces indicate that the carapace was high-domed even though a marginal gutter was developed. Ventrolateral surfaces show lines of minute striae that radiate from central areas of tiny punctations. Costals, neurals and plastron are smooth, as in Otwayemys but the outer carapace edge has a reticulated network of faint polygonal incisions as in Meiolania and the Australian chelids.

Sockets in peripherals four, five and six, each confined within the lower internal surface, indicate that axillary and inguinal buttresses were undeveloped. The inguinal process contacts peripheral five in Platychelys (Lapparent de Broin 2000) and peripheral seven in Notoemys (Fernandez and de la Fuente 1994). In Sunflashemys, the peripherals are faintly spinous, rough and microvermiculate, showing a cancellous striated histology resembling that of Cretaceous chelids from Patagonia (Lapparent de Broin and de la Fuente 2001), but the texture is weaker than in the isolated peripheral LRF459 identified as indeterminate chelid (Chapter Eight; Fig. 37).

In Notoemys, bridge peripherals carry two costal rib ends, an unusual feature. In Sunflashemys, one bridge peripheral (perhaps the third) seemd to show two costal rib end sockets. The ventral edge of peripherals three and four tapers sharply, and a sutured carapace-plastron connection is indicated. The dorsomedial section of the peripherals may be only weakly sutured to the adjacent distal costals, another feature resembling platychelyids (Notoemys) and chelids.

The fourth peripheral of Sunflashemys contains an inflated hollow cavity, a musk gland chamber, which apparently opened from a sinus on the ventromedial surface. Musk glands are widely distributed among turtles and the bony canals and gland ducts in fossil groups echo the patterns in living representatives (Weldon and Gaffney 1998). The pores or openings are in the mesoplastral mid-region of the bridge in Kayentachelys, in bridge buttresses in Xinjiangchelys (Peng and Brinkman 1993) and macrobaenids (Brinkman and Peng 1993), but are absent in . Musk duct glands are apparently unknown in fossil pleurodires from South America (Marcelo de la Fuente persn. commun.), however the axillary position of the duct in Sunflashemys is the same as in Platychelys and Australian chelids, which have two

71 inframarginal musk glands on each side, in the peripheral-plastral suture close to inguinal and axillary openings (Cann 1998; and pers. obs.). The gland cavities in Sunflashemys are very large.

Pygal (Fig. 20) Type material includes the posterior section of a thick robust pygal plate, showing a curved recess medially to accommodate the ilium. The similarity to Elseya is interesting (pers. obs.), indicating that the ilium was distally expanded, contacted the eighth costal and was sutured but probably not fused to the carapace.

Axial skeleton Cervical vertebrae (Fig. 22) Vertebral elements at the Tyrone’s site were mostly broken into minute pieces that cannot be reassembled. A neural arch fragment, interpreted as that of the first or axial vertebra, and three cervical vertebrae, interpreted as the fourth, fifth and sixth, plus referred specimens from other locations, permit a partial reconstruction.

The axial neural arch specimen includes the dorsal part of the neural canal, the spine and postzygapophyses. The spine is tall and sail-like, directed anteriorly, divided at the rear into two fine blades forming small tubercles above the postzygapophyses, which are positioned close to the neural canal.

AMF105649, an opisthocoelous specimen with huge apophyses and small intercentral bumps on the rear cotyle is assigned to Sunflashemys as a third cervical. The fourth cervical (type specimen and LRF15) is biconvex with oval central facets that are taller than wide, tapering ventrally and a shallow ventral keel. The low neural arch has paired midline tubercles at the highest point. Zygapophyses are widely splayed, the postzygapophyseal facets are horizontal, separated from each other and oriented laterally.

The fifth cervical is procoelous with small parapophyseal bumps (intercentral articulations) located on the oval anterior cotyle. Postzygapophyses are spread but directed more posteriorly than in the preceding vertebra.

72 The sixth cervical has a circular anterior cotyle and tall subtriangular posterior condyle. Widely separated from the transverse processes, there are very large parapophyses with articulation facets forward of and below the central cotyle. Thick buttress-like laminae extend from these processes onto the middle of the ventral surface of the centrum. The robust neural arch is a broad columnar pedicle with a distinctive rear-opening cavity above the postzygapophyses as in modern chelids such as Elseya (pers. obs.). In the sixth cervical from the type location, the rear section of the neural tower is missing but the structure is demonstrated in specimens from other locations.

AMF68245, an isolated biconcave vertebra from an unknown location at Lightning Ridge, qualifies as a seventh of Sunflashemys on the basis of the oval tapered cotyle, huge neural pedicle and triangular pocket above the postzygapophyses. In this specimen, the parapophyses are small, like those of the fifth rather than the sixth cervical. However there are other biconcave centra (for example, LRFR465) with circular anterior cotyle and large parapophyseal processes resembling those of the sixth cervical. LRFR465 is one of a number of unusual biconcave centra from various locations that might be assigned to either Spoochelys or Sunflashemys, a dilemma that will only be resolved with discovery of further material.

The eighth cervical vertebra is assumed to be weakly opisthocoelous or biconvex, given the biconcave seventh and flattish anterior facet of the first thoracic. However given the degree of oddity in the anterior thoracic vertebrae, it is impossible to identify isolated specimens as possible eighth cervicals for Sunflashemys. AMF127999 may be a plausible neural arch of an eighth cervical, corresponding with the anterior thoracics because the top of the ribhead facet is level with the zygapophyses. In AMF127999, the huge ribhead facets cover the whole neurocentral suture, showing that the ribs were massive and weakly attached to the centrum. There is also resemblance to the eighth cervical of Caribemys (de la Fuente and Iturralde- Vinent 2001) in the long low pedicle with small poszygapophyses close to each other and facing ventrally.

As with the seventh cervical, details of the eighth cervical centrum are unclear. LRFR466, a biconvex centrum with strong parapophyses like those of the sixth

73 cervical may be assignable to Sunflashemys, as the posterior condyle and placement and structure of the transverse processes are identical to the fourth from Tyrone’s. Nonetheless, although the specimen is similar to the purported eighth of Otwayemys (Gaffney et al. 1998), neither the transverse processes nor the posterior central condyle ‘match’ the neural arch of the eighth described above (AMF127999).

Sunflashemys is obviously a short-necked turtle and the central articulation formula is (2( (3( (4) )5) )6) )7( (8I or (8). While this is similar to the pattern in many cryptodires (Vaillant 1880; Williams 1950), pleurodire-like features predominate in the cervical series. Transverse processes are large and triangular in dorsal view, located in the middle of the centra, which are sharply pinched with low rounded keels in anterior and posterior cervicals. Central condyles form cylinders for lateral rotation; the tendency for ventral keels to develop a small articular facet below and slightly behind the anterior condyle is a feature of extant chelids such as Elseya (pers. obs.); and it may be significant that anterior central facets are smaller and narrower than rear facets, again as in Elseya.

Central condyles and cotyles are progressively larger and the neural arch is progressively taller and thicker along the series. Postzygapophyses do not form a continuous articulation surface, but this is also the case in Notoemys. Facets of the zygapophyses are flat. At the rear of the series, the neural pedicle isolates the postzygapophyses from the centrum, and prezygapophyses are held in infra- postzygapophyseal fossae that permit lateral flexion. The deep pocket above the postzygapophyses is another chelid-like feature.

Cervical ribs are plesiomorphic for turtles, widely distributed among basal cryptodires, and lost below Pleurodira. The size of the parapophyses in the Lightning Ridge taxa may differ between individuals and possibly the cervical ribs were variably ossified, perhaps due to ontogeny or sexual dimorphism. No cervical ribs were found at the Sunflashemys type locality, even though cartilaginous skull material was preserved. The parapophyses of Sunflashemys resemble those of Meiolania in size, but the projections on the sixth cervical are apomorphically large, placing the parapophyseal facets forward of and ventral to the centrum where they do not impede the lateral hinge function of the articulation between fifth and sixth

74 cervicals. There is no reason to assume that cervical ribs prevented lateral neck movement. By providing extensive attachment surfaces for muscles and ligaments, cervical ribs may even have strengthened lateral flexion. Large transverse processes in pleurodires are correlated with the lateral predatory strike (Pritchard 1984), and perhaps loss of cervical ribs in side-necked turtles was related to the need for attack speed, rather than power during defensive neck retraction. In cervical structure, apart from the double rib articulations, the primary difference between Sunflashemys and forms such as Platychelys, Dortoka and the short-necked chelids is the biconvex fourth: in these latter groups, it is the fifth cervical that is biconvex (Lapparent de Broin 2000).

Sacrals and sacro-caudal (Fig. 23) Sacral centra of Sunflashemys are more generalized than those of Spooche,lys, being deeper and less flattened. In Sunflashemys, the tenth thoracic vertebra is centrally fused with the first sacral - a pleurodiran synapomorphy. In the Lightning Ridge taxa, attachments of the transverse process to the sacral vertebrae are variable - sometimes fused, sometimes apparently cartilaginous or very loosely sutured. Sunflashemys has a sacro-caudal vertebra variably fused to the second sacral, another derivation shared with Spoochelys and Meiolania. This feature is also typical of pleurodires (Hoffstetter and Gass 1969), seen in Proterochersis and Notoemys zapatocaensis (Rueda and Gaffney 2003).

Caudal vertebrae (Fig. 23) Unfortunately, no caudal vertebrae were recovered at Tyrone’s, but turtle caudal vertebrae from Lightning Ridge comprise an exceptionally uniform assemblage and Sunflashemys is well represented among numerous specimens from other locations. Anterior caudals for Sunflashemys are separated from those of Spoochelys by the larger transverse processes, circular in section. Caudal series for both taxa are completely opisthocoelous, with strongly developed haemal keels posteriorly. Fully opisthocoelous caudals are shared with Platychelys (Gaffney and Meylan 1988) and Meiolania.

75 Pectoral girdle Type material includes a fragment of glenoid, a pair of scapula processes and distal sections of the acromial processes. There is no glenoid neck, the primitive condition. The scapula has a surface texture of irregular suture spines at the distal (dorsal) apex, coinciding with the ridged articular surface of the first thoracic rib. The acromion is more derived than that of Spoochelys, subtriangular rather than triradiate in section, tapering to a blunt end distally where there is a rounded protuberance, rather than the acromial spike of Spoochelys and Meiolania.

Humerus (Fig. 24) The humerus from the Tyrone’s site is near-complete. As in Meiolania, the medial process is longer than the lateral process. The humerus of Sunflashemys is more gracile than that of Spoochelys and the medial process is markedly finer and more elongate. In dorsal view, the head is twisted diagonally, that is, inclined laterally, with a sharp jutting edge along the ventral margin. A well-developed lateral shoulder or shelf is present on the humeral head, a pleurodire synapomorphy (Gaffney et al. 2006). The intertubercular fossa is a broad convexity without the web between medial and lateral expansions seen in Proganochelys and Meiolania.

As in Meiolania and , distal articular condyles are globular, exposed distally as well as ventrally, unlike most turtles in which the articular surfaces are poorly differentiated. The entepicondyle is thicker dorsoventrally than the ectepicondyle, as in Meiolania. The ectepicondylar groove is closed, opening on the ventral surface proximal to the lateral condyle. In Proganochelys and Meiolania, the foramen opens lateral to the condyle. Lateral to the ectepicondylar foramen, a bony rim or shelf curves distally, finishing on the ventral surface of the capitellum (radial articulation). This suggests enlarged areas of attachment for heavy extensor muscles of the forearm; the feature seems more strongly developed than in Proganochelys.

Ulna A well-preserved proximal section of a left ulna and the distal portion of the right ulna were retrieved from Tyrone’s. Although less robust than that of Spoochelys, the ulna has the same very high olecranon process and is subtriangular in proximal view. The bicipital tendon attachment is prominent and continuous with a low flange

76 curving medially and proximally on the shaft. The bicipital tubercle is also continuous dorsally with a heavy ridge extending distally from the proximal articular surface along the shaft, a diagnostic meiolaniid feature also seen in Spoochelys. The ulna shaft is very slender mediolaterally.

Radius Radial morphology in turtles is conservative, with little variation across many groups. In Sunflashemys, the proximal articulation is flat and hemispherical, with a small subsidiary articular surface or facet dropping towards the radio-ulnare ligament attachment on the dorsal side.

Femur In Sunflashemys the head of the femur is flatter than in Spoochelys, forming an arc of around 180o that is hooked or notched dorsoventrally.

Manus and pes (Fig. 24) A number of manual and pedal elements were recovered from the Tyrone’s site and several specimens are referred. Identifications are made with great hesitation as the material is disarticulated and incomplete. The medial centrale appears similar to that of Meiolania, a relatively large element, convex proximally and flat distally. The small distal carpals or tarsals are subspherical, oval or elliptical. Metacarpals (or metatarsals) have strongly developed overlap facets and cylindrical undivided distal articulations. Proximal acetabula of the manual phalanges are circular convexities with the ventral rim enlarged and occupying up to half the phalanx, as in Proganochelys. Distal articulations of some of the manual and pedal phalanges are subdivided but proximal acetabula of the unguals are simple circular cotyles, or faintly saddle- shaped. The ungual shaft is constricted at the claw base and weakly recurved, but the unguals are broader and more spatulate than those of Elseya, for example. Sunflashemys is a short-handed turtle with only two phalanges in each digit, the archaic terrestrial pattern for turtles.

77 Pelvic girdle The only pelvic fragment retrieved from the Tyrone’s location was the acetabulam, which was recovered after being vigorously processed through mining machinery. A chunky, robust element, it shows the typical triradiate pelvic sutures but little else.

Tibia The tibia distal fragment from Tyrone’s is suboval in distal view, subtriangular in section at the broken shaft, with the flatter surface on the dorsal side.

Discussion It must be emphasized that many aspects of the Sunflashemys skeleton are uncertain - the dermal roof and anterior section of the skull is missing, the carapace is fragmentary and plastron unknown. Recovery of further articulated material may lead to modification of the description and interpretation presented here.

In the interim, it appears that Sunflashemys and Spoochelys are united by the extended basisphenoid edge of the open cavum labyrinthicum, narrow costo-vertebral tunnel, tall central facets and posterior position of the postzygapophyses in rear cervicals, and central fusion of the tenth thoracic vertebra with the sacrum. Generic distinction from Spoochelys is well supported. Differences include the pterygoid indentations, larger basioccipital tubercles, finer scute texture and shallow scute sulci, carapace morphology and generally less blocky appendicular skeleton. A clade consisting of Sunflashemys, Spoochelys, Opalania and Meiolania is supported by epipterygoid structure, and postcranial synapomorphies such as the proximodorsal ridge of the ulna and opisthocoelous caudals.

Sunflashemys differs from Otwayemys in the shallow scale sulci, larger first neural, absence of bridge-peripheral fontanelle, structure of cervical vertebrae and first thoracic vertebrae; and from Chelycarapookus in the less prominent first thoracic rib and longer first thoracic vertebra.

The basicranium of Sunflashemys, like that of Spoochelys, closely resembles Notoemys. Bony separation of the canalis nervi facialis from the canalis cavernosus is a primary pleurodiran synapomorphy, which in combination with strong prootic

78 exposure, unfloored cavum labyrinthicum and open recessus scalae tympani suggests closer phylogenetic affinity to pleurodiromorph stem taxa than to cryptodires.

Simpson (1938: 232: 7C) in his description of the pterygoid of Crossochelys (AMNH31610) incorrectly labeled the rear section of the canalis nervi facialis as the ‘S. C. I.’ (‘sulcus caroticus internus’), the internal carotid canal. Gaffney (1983: 443: 60A) used the Crossochelys pterygoid (AMNH31610) to reconstruct the basicranium of primitive meiolaniids, following Simpson’s interpretation. In the Lightning Ridge turtles, the foramen caroticum basisphenoidale is in the anterior section of the basisphenoid, widely separated from the pterygoid, and it is likely that the same condition pertains in Crossochelys and Niolamia, with the carotid artery traversing the ventral surface of the basisphenoid unhindered by bone.

In Sunflashemys, the small pterygoid sheet underlying the canalis nervi facialis is not sutured to the overlying basisphenoid and is not homologous with the pterygoid floor of the carotid canal in cryptodires, which is strongly sutured to adjoining elements. This accords with morphology in Tertiary meiolaniids in which the posteromedial pterygoid extension is separated from adjacent elements by an open fissure. The caudomedial extension of the pterygoid that engulfs the carotid artery in Tertiary meiolaniids is an independent acquisition.

Although the pterygoid is separated from the basioccipital in Condorchelys and Heckerochelys, these forms lack the pleurodiran condition of the canalis nervi facialis. Inner and middle ear structures of Kayentachelys are apparently more advanced, in the strong sutural contact between prootic, basisphenoid and opisthotic, complex cavum-acustico jugulare, development of the foramen jugulare posterius and medial position of the incisura columellae auris. In cryptodiromorphs and basal cryptodires (Mongolochelys, Kallokibotion, paracryptodires and primitive eucryptodires), the interpterygoid vacuity is lost, the pterygoid conceals part of the cavum labyrinthicum or contacts basioccipital and/or exoccipital, and the recessus scalae tympani is closed.

Given lack of comparative cranial data for ancestral pleurodires, it is impossible to assess if layout of the palatine and carotid arteries in Sunflashemys, and their

79 topological relationship to the interpterygoid vacuity and basipterygoid processes is typical of pleurodiromorphs. Plainly though, the interpterygoid vacuity and foramen caroticum basisphenoidale in Sunflashemys is more primitive than in Euraxemys and Dirqadim; these structures are described in detail by Gaffney et al. (2006).

No known pleurodire has an epipterygoid and absence of this element is a robust synapomorphy for the crown group (Gaffney et al. 1991; Shaffer et al. 1997; Gaffney et al. 2006). Structure and contacts of the epipterygoid in Sunflashemys and Spoochelys resemble Meiolania. Epipterygoid morphology in the Lightning Ridge turtles suggests that loss of this element occurred in pleurodiromorph stem taxa below Platychelyidae, by fusion with the pterygoid. The typical chelid-like structure in which parietal and pterygoid form the anterior margin of the foramen nervi trigemini and the posterior edge of the foramen interorbitale can be viewed as the result of this relatively simple modification.

Anterior thoracic vertebrae of Sunflashemys exhibit features consistent with a basal phylogenetic level. In the absence of comparable material, systematic, functional and developmental implications are uncertain, however the peculiarities must be interpreted as primitive. The loose attachment of ribheads, thin neural bones, persistence of the postzygapophyseal arch, and undeveloped neural blade, at least in anterior thoracics, present a unique blend of structures that might be construed as more primitive than in Proganochelys and Palaeochersis. Osteogenetic relations of dermal bones in the turtle carapace are controversial (Zangerl 1969; Lee 1997; Rieppel 2002; Joyce et al. 2008; Li et al. 2008). Morphology of the neural plate in Sunflashemys suggests that in at least one basal turtle group, anterior neural bones may have developed by expansion and fusion of prezygapophyses and neural spine, not from fusion of dermal armour with the endoskeleton (Fig. 21).

Bridge peripherals in Sunflashemys are elongated with a narrow dorsal gutter, suggesting some aquatic adaptation, correlating with podial morphology that is more derived than in Spoochelys. Nonetheless, Sunflashemys is a short-handed turtle with a domed carapace, as in primitive land turtles such as Proterochersis, Palaeochersis (Joyce and Gauthier 2003) and meiolaniids.

80 Sunflashemys offers interesting opportunities for additional comparative investigation and documentation of: i) micro-histology of the inner ear and columella stapes; ii) morphology of the anterior carapace and anterior thoracic vertebrae; and iii) contact between epipterygoid and basisphenoid rostrum at the front of the braincase, an unusual feature that is also present in Spoochelys.

In summary, Sunflashemys exhibits primitive conditions of the basicranium, inner and middle ear, resembling Jurassic forms such as Heckerochelys and Notoemys. Sunflashemys is sister-taxon to Spoochelys, also from Lightning Ridge, and a close phylogenetic relationship with the meiolaniids is strongly supported by synapomorphies of the epipterygoid, facial nerve, axial and appendicular skeleton. The basicranium of Sunflashemys agrees closely with Notoemys in middle and inner ear transformations, and postcrania exhibit platychelyid derivations - cervical vertebrae display a range of derived features consistent with lateral neck movement and the ilium was weakly sutured to the carapace. Presence in Early Cretaceous Australia of diverse groups of meiolanoid turtles displaying a limited array of pleurodiran synapomorphies suggests complex and very ancient radiations of pleurodiromorph stem turtles across Pangea.

81

CHAPTER FOUR

OPALANIA BAAGIIWAYAMBA N. GEN. ET SP. (MEIOLANOIDEA: SPOOCHELYIDAE) - A NEAR-POLAR LAND TURTLE FROM THE EARLY CRETACEOUS OF LIGHTNING RIDGE, NEW SOUTH WALES, AUSTRALIA

Opalania baagiiwayamba n. gen. et sp., a primitive terrestrial turtle from Lightning Ridge, New South Wales, is represented by sparse type material that clearly evinces a third meiolaniid-like taxon from the opal fields. Opalania exhibits a suite of transitional states and apomorphies otherwise restricted to the Meiolaniidae, and was originally proposed as the oldest meiolaniid (Smith 2006). Diagnostic features for the family as defined by Gaffney (1996) are not discernible in the type material, and in the phylogenetic analysis undertaken in the course of this study, Opalania is resolved as member of a clade containing Spoochelys and Sunflashemys, also from Lightning Ridge. These three taxa in the new family Spoochelyidae, are sister group to Meiolaniidae in the superfamily Meiolanoidea.

Opalania is characterized by large paddle-like cervical ribs and spongiform bone histology as in Tertiary meiolaniids. Curvature of the lower jaw and a lateral dentary shelf as in Niolamia and Meiolania indicate that the face was short and broad, with deep cheek flanges. The carapace is high-domed and unguals are hoof- like. Along the anterior carapace edge, triangular projections are formed by overfolded or ‘pleated’ marginal or possibly supramarginal scutes. With an extimated carapace length of ~700mm, Opalania is smaller than Meiolania platyceps, similar in size to Crossochelys and Chubutemys from Patagonia.

Opalania is rare in the opalised assemblages at Lightning Ridge, meagrely represented by bone elements from widely separated areas. Even so, if found in any

90 Cainozoic Australian locality, these specimens would be interpreted without hesitation as evidence of a meiolaniid-like form.

Opalania material consists of a lower jaw, cervical rib, articulated and associated carapace elements (peripheral, neural and costal, and a thoracic vertebra) and an ungual. The jaw from ‘Mr. K. Barlow of Grafton, New South Wales’ has been in the Australian Museum, Sydney, for many decades. Gaffney (1981: 28) did not examine the original specimen, but compared a cast of the specimen AMNH16239 to Plesiochelys and , identifying it as ‘Testudines indeterminant’ with ‘[no] features necessarily barring it from the Pleurodira, although it is most likely a cryptodire’. The carapace pieces are from T-Bone Extension, excavated by opal miners Rob and Debbie Brogan; the ungual is from Jag Hill; and the cervical rib was found by the author in a tailing heap from Emu’s Field on the Coocoran, west of Lightning Ridge.

SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996 Family SPOOCHELYIDAE n.

Opalania n. gen. Diagnosis. As for only known species. Etymology. ‘Opal’ for the glorious substance; ‘ - lania’ for the group.

Opalania baagiiwayamba n. gen., n. sp. Type specimen. Australian Museum, Sydney, AMF72274, right lower jaw ramus.

Locality and horizon. Finch Claystone Facies of the Wallangulla Sandstone Member of the Griman Creek Formation. Early - middle Albian (Exon and Senior 1976; Morgan 1984; Burger 1986, 1995); middle - late Albian (Dettman et al. 1992).

91 Etymology. ‘baagii’ - mother’s mother; ‘wayamba’ - short-necked turtle in the language of the Yuwaalaraay (Dodd et al. 2003), traditional owners and custodians of black opal country at Lightning Ridge.

Diagnosis. As for monotypic genus and species. Lower jaw with narrow triturating surface lacking ridges and denticulation, broadest at very large fossa meckelii; long splenial-dentary contact on ventral rim of ramus; contour of ramus indicating short broad face. Sharing with Tertiary meiolaniids – dentary deep with rounded constriction of jaw ramus posterior to granular rhamphothecal surface (as in Niolamia); lateral shelf of dentary indicating low cheek flanges; splenial-dentary contact restricts angular exposure; contact of splenial and dentary in meckelian sulcus anterior to foramen intermandibularis medius (also in Spoochelys); coronoid forms posterior margin of foramen intermandibularis medius but does not contribute to triturating surface; supernumerary element - ?postsplenial. Cervical ribs large, free, deep dorsoventrally and curved concave posteromedially, sigmoidal in proximal view with large tuberculum facet facing proximally; overfolded or pleated scutes producing triangular projections on anterior carapace edge; bones with surface texture of small vermiculate grooves, punctations and strongly-defined curvilinear internal vascularisation. Low median ridge on carapace; and low dorsal ridge on short stocky hoof-like unguals.

Referred specimens. Cervical rib AMF127976; peripheral and costal fragment LRF69; thoracic vertebra with attached neural LRF73; manus or pes ungual LRF17.

Description and comparison Lower jaw (Figs. 25, 26) AMF72274 is complete, missing only the symphysis. It is much deeper dorsoventrally with a higher coronoid process than the lower jaw of Proganochelys. Jaw curvature indicates that Opalania had a short broad face similar to Niolamia. In dorsal view, the resemblance to Proganochelys is striking because the triturating section is slender and the ramus broadens lateral to the fossa meckelii. Opening predominantly inwards, the fossa meckelii comprises almost one third of the length of the ramus. In Meiolania, the lateral wall of the fossa meckelii

92 is lower than the medial wall, an apparent autapomorphy. The lower jaw of Opalania is slightly longer than that of Spoochelys but twice as deep.

Dentary The dentary has the usual contacts with surangular, coronoid, splenial and angular. The triturating surface is narrow, flat and ribbon-like. Gaffney (1996) considered the narrow triturating surface as diagnostic for meiolaniids, but the unexpanded surface is primitive, even narrower in Glyptops and Dracochelys. In Opalania, triturating margins are very low, without denticulations. A well-developed labial ridge is also given as a meiolaniid character (Gaffney 1996), but the labial ridge is unexpanded in Opalania and Niolamia, indicating that the high labial ridge in Meiolania is autapomorphic for that taxon.

In most turtles the front of the ramus is pitted and grooved (Gaffney 1979). In Opalania, as in Niolamia, the rhamphothecal surface has a granular texture, delimited by a ‘distinct constriction … [extending] obliquely downwards and forwards’ (Woodward 1901: 173) from the rear triturating margin.

Triturating ridges are equal in height except posteriorly, where the labial ridge forms a slight posterolateral spur as in Meiolania, higher than the lingual ridge. The spur is continuous with a shallow shelf indicating the position of the maxilla during occlusion, which suggests deep cheek flanges, a meiolaniid feature. Also as in Meiolania, the dentary extends far back on the lower rim of the ramus, ventral to the foramen intermandibularis caudalis.

The sulcus cartilaginis meckelii is unroofed and shallow. The shallow sulcus is a primitive feature also seen in Glyptops, but the condition in Opalania resembles Proganochelys because rather than sloping ventrolaterally from the lingual triturating ridge as in other turtles, the dentary slopes strongly ventromedially. In Meiolania, the sulcus is a large channel, oval in section. In Opalania as in Proganochelys and Meiolania, the dentary is narrow in section below the meckelian sulcus.

93 In most turtles, the foramen dentofaciale majus in the dorsolateral surface of the dentary connects to the canalis alveolaris inferior, a nutrient canal starting at the foramen alveolare inferius in the fossa meckelii and travelling above the meckelian sulcus along the jaw ramus (Gaffney 1979). The foramen dentofaciale majus is absent in Opalania and Meiolania (Gaffney 1983). (Specimens AMF58099 and AMF69366 from Lord Howe Island have a small foramen in the appropriate position that is not connected to the canalis alveolaris inferior; pers. obs.). It is unclear whether this foramen is present in Proganochelys (Gaffney 1990). If not, absence of the foramen dentofaciale majus may be a meiolaniid synapomorphy.

Splenial A splenial is present in Palaeochersis, paracryptodires (baenids), plesiochelyids, Solnhofia, lindholmemydids, indeterminate in Kallokibotion and may be present in Dracochelys. Romer (1956) reported the splenial in Platysternon and emydines, but among living turtles the splenial is present only in chelids, a feature separating them from pelomedusoids.

The splenial in Opalania contacts the prearticular posterodorsally, the coronoid anterodorsally, the dentary anteriorly and ventrally, and the angular posteriorly. The lower margin of the sulcus cartilaginis meckelii is formed by the splenial, but the anterior extent is uncertain due to breakage. There is a small foramen intermandibularis oralis.

Among turtles, only Proganochelys has a splenial as large as that of Opalania, covering most of the inner jaw and extending along the lower rim of the ramus. The splenial is large in Kayentachelys, apparently dropping ventrally at the symphysis (Sterli and Joyce 2007). In Proganochelys, the splenial covers a large posterior section of the meckelian sulcus. Opalania exhibits an important derivation otherwise known only in Meiolania: the wall of the foramen intermandibularis medius on the lateral side (that is, the labial side) is formed by slender contact between dentary and splenial spanning the meckelian sulcus. In Meiolania, the foramen intermandibularis medius was identified as the anterior opening between dentary and splenial (Gaffney 1983). AMF72274 demonstrates that the foramen intermandibularis medius in Meiolania is actually the foramen

94 marked ‘?’ by Gaffney (ibid.: 451: 62c). The dentary-splenial contact anterior to the foramen that is seen in Opalania has lengthened in Meiolania, and the foramen intermandibularis medius has moved backwards along the meckelian sulcus.

In Opalania, the splenial forms the front margin of the foramen intermandibularis caudalis and may also form part of the ventral rim of that foramen, as in some specimens of Meiolania (pers. obs.).

Angular The angular is very small, restricted to the rear lower surface of the jaw, contacting the articular posteriorly, the prearticular dorsally, the splenial and dentary anteriorly and the surangular laterally. The angular apparently forms part of the ventral margin of the foramen intermandibularis caudalis.

In Meiolania, exposure of the angular on the inner jaw surface is reduced by dentary-splenial contact. In AMF58099 from Lord Howe Island, splenial and dentary are missing, revealing that the angular projects forward below the coronoid process but finishes short of the meckelian sulcus. It is unclear whether this is also the case in Opalania, and the structure in Niolamia and Otwayemys is unknown. The short angular, overlain lingually by long dentary-splenial contact may be a meiolaniid synapomorphy. The condition is derived over Proganochelys but differs markedly from crown group turtles in which the ventral jaw surface is formed by the angular, which projects forward below the meckelian sulcus (Gaffney 1990).

In Opalania, an extra suture is developed on the rear ventral rim of the ramus, suggesting a narrow rectangular supernumerary element interposed between prearticular and angular. I am reluctant to identify a postsplenial, previously unreported in turtles, although two splenial elements are known in some primitive reptiles (Romer 1956). Nonetheless well-preserved specimens of Meiolania (AMF58099 for example) show a similar formed suture in this position. This may be a retained primitive feature, and it is apparently absent in Proganochelys.

95 Surangular The surangular forms most of the outer rear surface of the ramus and most of the lateral wall of the fossa meckelii and as in Proganochelys, does not contribute to the coronoid process. The contact with the dentary extends back below the area articularis mandibularis.

The surangular forms the lateral surface of the area articularis mandibularis as in Meiolania; and the surangular-articular suture on the articular surface is shallowly indented. The foramen nervi auriculotemporalis is very large in Opalania and other meiolaniids, as in Araripemys and chelid pleurodires. It is also large in pleurosternids (Glyptops), possibly secondarily in that group, but is absent in plesiochelyids. Presence/absence of the foramen in Proganochelys is indeterminate, perhaps due to poor preservation.

Coronoid The coronoid has the usual contacts but is very small and laterally compressed. It forms the posterior margin of the foramen intermandibularis medius, as in Meiolania.

The dentary conceals the coronoid in Opalania to a greater degree than in Proganochelys, closely resembling Meiolania in which the coronoid does not extend onto the triturating surface (pers. obs.; contra Gaffney 1983). It is doubtful if the small coronoid of Proganochelys and Meiolania is ‘independently autapomorphic for both taxa’ (Gaffney 1990: 97). The coronoid in meiolaniids is derived over Proganochelys as it extends further anteroventrally on the inner jaw surface, but is primitive compared to other turtles.

In Opalania, the coronoid appears to extend posteriorly to a slender contact with the articular, thus forming most of the inner medial wall of the fossa meckelii. I can find no reference to a coronoid-articular contact among turtles (or primitive reptiles) so the condition is either unique to Opalania, or aberrant in AMF72274, or a preservational artifact. The coronoid finishes near the front of the fossa meckelii in other turtles. However in Solnhofia (TM4023) the coronoid extends along the edge of the fossa meckelii, reducing prearticular contribution to the margin of the

96 fossa (Parsons and Williams 1961: 85: 10, 11; Gaffney 1975: 9: lower stereophotograph). Gaffney (1990: 100) suggested that ‘dorsal expansion of [the prearticular] is involved in the change from a lateral-facing to a dorsal-facing opening’ of the fossa meckelii. If so, it might be surmised that rear development of the coronoid along the fossa meckelii occurred prior to dorsal expansion of the prearticular, hence this feature in Opalania would be a derivation from archaic morphology. The posterior coronoid extension is not apparent in Meiolania.

Articular The articular forms the posteromedial margin of the fossa meckelii and the medial two-thirds of the area articularis mandibularis, a squareish flat surface that slopes posteromedioventrally. Opalania resembles Proganochelys in poor development of the area articularis mandibularis and the slight dorsal projection of the posterior rim. A dorsal projection is also present in Proganochelys and Palaeochersis in which the retroarticular process is more strongly developed. The smaller process in Opalania is directed posteromedially, as in Meiolania. In Opalania, the foramen posterius chorda tympani is in the articular component of the retroarticular process, exposed in dorsal view. The retroarticular process appears to be absent primitively in both pleurodires and cryptodires (Brinkman and Nicholls 1991; Meylan 1996).

Prearticular The prearticular is a sheet-like rhomboidal element forming the dorsal and posterior margin of the foramen intermandibularis caudalis. It may be excluded from the fossa meckelii. The prearticular-articular suture runs along the medial edge of the area articularis mandibularis, an unusual feature. The prearticular forms the dorsal and posterior margin of the foramen intermandibularis caudalis.

Postcrania Cervical rib (Fig. 28) Proganochelys has cervical ribs 2 - 5 free and 6 - 8 fused; in Meiolania, 2 - 6 are free, 7 - 8 are fused. Only in these two forms are the free ribs large, transversely flattened, blade-like and dorsoventrally deep (Gaffney 1983; 1990; 1996; Joyce 2007). Cervical ribs of Meiolania are larger, longer and more tapered distally than those of Proganochelys. In both forms, there is a tuberculum facet for attachment

97 with the transverse process of the neural arch, and capitulum facet for attachment with the intercentrum or parapophysis. AMF127976, the cervical rib of Opalania, is broken distally but in general shape resembles cervical rib 5 or 6 of Meiolania. The rib is curved concave posteromedially, with the larger tuberculum facet facing proximally and it is sigmoidal in proximal view, features that are also present in cervical ribs of Meiolania. In Proganochelys, the articulation facets are equal in size and oriented medially and the ribs are flat, not curved.

Cervical ribs are rare among turtles, despite the prevalence of parapophyseal facets on the centra in primitive taxa. According to Joyce (2007) cervical ribs must be inferred for Mongolochelys and Hangaiemys; and small ribs are known for Ordosemys. Further groups, for example Kayentachelys, Mesochelys and Xinjiangchelys have parapophyseal facets or projections but associated cervical ribs have not been found. Cervical ribs are absent in Palaeochersis (Sterli and Joyce 2007), however cervical centra of some fossil and extant chelids bear small ‘inferolateral tuberosities’ (de Lapparent de Broin and de la Fuente 2001) and parapophysis-like facets (pers. obs.), suggesting that cervical ribs may have been present among basal members.

Peripheral (Fig. 27) LRF69 consists of two fragments from the left side, being part of the second peripheral and the anterolateral section of the first costal. The suture between these two elements is strongly interdigitated. The bone is thick, the surface patterned with grooves, punctations and small channels, and internal texture shows curvilinear vermiculate cancelli, the typical histology as described in meiolaniid material from Rio Negro, Argentina (de Broin and de la Fuente 1993) and Meiolania (Scheyer 2007).

The dorsal surface has broad, heavily-incised scute sulci, delineating the lateral section of marginal two, the medial part of marginal three and the anterolateral section of the first pleural. The medial edge of the specimen was broken during excavation along the deep first vertebral scute sulcus. Opalania resembles Proganochelys in the depth of these sulci.

98 In the same peculiar manner as the front of the carapace in Meiolania, the outer peripheral margin in Opalania is overfolded, producing an angular, slightly scalloped outline. AMF57984, a second peripheral of Meiolania has small triangular stepped scales on the outer edges, described by Gaffney (1996: 13) as components of the marginals. Configuration of the front carapace margin in Meiolania is highly variable, but the same ‘pleated’ structure in Opalania and the similarity to Spoochelys, in which anterior marginals are constricted into tiny triangular shelves between supramarginals, strongly suggests that supramarginals are present in meiolaniids primitively. In LRF69, the fold is formed at the sulcus between marginals two and three, with marginal two partly overlying marginal three.

On the visceral surface, part of the long first thoracic rib is preserved, broken distally but doubtless extending to the adjacent peripheral. The rib is broad, flattened and tilted so its anterior edge is more ventral. The axillary buttress would impinge slightly onto the costal. Restriction of the buttress to the peripherals is given as diagnostic for meiolaniids (Gaffney 1996) but this is primitive for turtles. A small circular foramen in the peripheral resembles those seen in Meiolania AMF57984. In Proganochelys there is an overhanging rim at the front, less prominent in Meiolania. This rim is absent in Opalania and ventral peripheral contours are smooth and gradual.

Thoracic vertebra and neural (Fig. 27) LRF73, an anterior thoracic vertebra (possibly the second) with a rib-head, partial neural and costal fragment attached, is from the same individual as LRF69. Vermiculate internal structure is evident and the dorsal surface is microtuberculate. The vertebra is hourglass-shaped, elongate and the shallow centrum is V-shaped, slightly rounded ventrally, and straight in lateral view. The rib neck is subtriangular in section, the ribhead is enlarged and sutured, not fused to the vertebra. At the front of the vertebra, the costo-vertebral tunnel is low because the midline neural blade is undeveloped, but more posteriorly the blade is longer and the tunnel is higher. The neural canal is oval, taller than wide anteriorly, but circular posteriorly. There is no evidence of a suture between the neural plate and the vertebra. The neural is rather narrow with a straight lateral margin, sutured to a small section of

99 costal bone. The suture between this and the following neural crosses the midsection of the vertebra. There is a low midline peak along the dorsal carapace surface, at least anteriorly, unlike the flat condition in Meiolania.

In LRF73, the neural and proximal section of the attached costal are extraordinarily thin compared to the thickness of bone in LRF69, the associated peripheral and costal. Bone on the carapace midline is only about 1 mm thick, an interesting similarity to Sunflashemys and Chinlechelys tenertesta from the Late Triassic of New Mexico (Joyce et al. 2008). Extreme thinness and fragility of costal bones in Meiolania accounts for much of the difficulty in reconstruction of the carapace.

Manus or pes ungual (Fig. 28) Weathered and broken distally, LRF17 resembles meiolaniid unguals from Lake Pitikanta (Etadunna Formation) in South Australia (Gaffney 1996) and Lord Howe Island. The distinctive meiolaniid bone texture is evident and the hoof-like morphology shows no aquatic adaptation. The articular surface is flat, undivided and subcircular, slightly wider than tall, and the surface slopes anteroventrally so the dorsal edge is proximal to the ventral margin, as in Meiolania. The specimen shows the faint lateral constriction ventrally near the articular facet that is present in unguals of the Lake Pitikanta meiolaniid, but there is a low midline ridge on the dorsal surface that is absent in Tertiary meiolaniids. The specimen is unlike unguals of the smaller Lightning Ridge turtles, which are more slender and curved.

Discussion Despite its limitations, the Opalania material presents a unique blend of archaic structures and apomorphies otherwise encountered only Tertiary meiolaniids. The only diagnostic characters available in Opalania that overlap those defined for Meiolania by Gaffney (1996) are the unexpanded triturating surface (which is primitive for turtles), high labial ridge (absent in Opalania and Niolamia) and free ribs on posterior cervicals (one cervical rib specimen is known for Opalania, but its serial placement is uncertain).

Diagnosis of Opalania as a meiolanoid is substantiated by features such as dentary/splenial contact spanning the meckelian sulcus anterior to the foramen

100 intermandibularis medius (shared with Spoochelys and Meiolania), paddle-shaped cervical rib, bone histology, and the scalloped carapace edge formed by overfolded scute margins (marginals reduced to small shelves).

Spoochelys and Sunflashemys are more gracile, with differences in carapace, scute texture and ungual morphology. The smaller Lightning Ridge taxa are represented by abundant material, in contrast to the sparse remains of Opalania, which are blockier and larger, implying greater resistance to pre-burial and post-excavation wear. The implication is that Opalania preferred habitats distant from the swamp forest and stream-bank settings favoured by the smaller forms.

The Victorian turtles are smaller than Opalania and differ in scute and bone texture. Unlike Opalania, Chelycarapookus has an expanded costo-vertebral tunnel, and Otwayemys is separated by the narrower triturating surface angled ventromedially, high labial ridge, absence of the dentary shelf accommodating the overlapping maxilla, and in morphology of the carapace margin and thoracic vertebrae.

In summary, Opalania is referred to the Meiolanoidea on apomorphies of the lower jaw, cervical ribs, unguals and bone histology. Opalania and the two smaller Lightning Ridge taxa are assigned to the family Spoochelyidae, sister-group to the Tertiary meiolaniids. Spoochelyids provide evidence of diverse and previously undocumented radiations of meiolaniid-like taxa in the southern hemisphere, pre- dating the break-up of Pangea. Primitive features suggest affinities with the most basal turtles and the possibility of a Triassic origin. A biochron from early Mesozoic to Holocene is indicated for the Meiolanoidea, the greatest evolutionary longevity for any turtle group.

101

CHAPTER FIVE

NEW CRANIAL MATERIAL OF A MEIOLANIID CF. WARKALANIA FROM THE MIOCENE OF RIVERSLEIGH, NORTH QUEENSLAND

Alex Ritchie of the Australian Museum, Sydney, was the first to recognise meiolaniid tail ring sections at Pancake site, Riversleigh (Oligo-Miocene), in far north Queensland. Discovery of further elements and a partial skull, the oldest cranial material for Australian meiolaniids, permitted description of Warkalania carinaminor Gaffney et al. 1992. The holotype, a right squamosal and referred specimens from the type locality (Gaffney et al. 1992), apparently consisted of ‘more than one individual and more than one species’ (Gaffney 1996: 86). Subsequently several sites at Riversleigh have produced meiolaniid material. Vertebral fragments, conical horn cores and carapace shards suggest largeish forms and despite the low abundance, at least four taxa (four species in two genera) are identified (White 1997).

Unfortunately the type material of Warkalania is missing, but in 2001 an excellent meiolaniid basicranium AR18672 was recovered from Cadbury’s Kingdom at Riversleigh. AR18672 is the best-preserved meiolaniid basicranium older than the Pleistocene Lord Howe Island material, recording details of middle and inner ear, otic chamber, primary neurocranium and sutures. The type material did not preserve sutures or details of major soft tissue canals (Gaffney et al. 1992).

AR18762 provides important information on meiolaniid evolutionary history. Analysed here in conjunction with the new meiolaniid-like turtles from Lightning Ridge, the meiolaniid cf Warkalania from Riversleigh illustrates a range of transitions between Early Cretaceous and Tertiary meiolanoids.

106 SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996 Family MEIOLANIIDAE Gaffney 1996 Genus Warkalania Gaffney, Archer and White 1992

Warkalania sp. (Fig. 29) Material. AR18672, an articulated partial braincase, consisting of parts of the basisphenoid, basioccipital, pterygoid, exoccipital, opisthotic, prootic and quadrate; preserving the cavum acistico-jugulare, some of the canalis cavernosus, otic chamber, cavum tympani and incisura stapes.

Locality and horizon. Cadbury’s Kingdom, Carl Creek Limestone, Riversleigh Station, north west Queensland. Early Miocene (Archer et al. 1989; Archer et al. 1997).

Description and comparison Where corresponding elements are known, on the basis of comparison with previously described material (Gaffney et al. 1992; Gaffney 1996), this new material is very similar to W. carinaminor and is identified as the meiolaniid cf Warkalania pending recovery of more informative material.

Quadrate The quadrate appears to form most of the cavum tympani (which is intermediate in size between that of Niolamia and Meiolania) and the bony block behind the incisura columellae auris. The quadrate is overlain posterodorsally by a thin sheet of the opisthotic, a contact that is at least partially unsutured, the primitive condition (Fig. 29). There is no distinct processus trochlearis oticum, despite the barreled shape of the otic chamber. AR18672 preserves only the dorsal arch of the incisura columellae auris, so it is unclear whether the incisura was closed ventrally by the heavy contact of squamosal and quadratojugal that is seen in Meiolania.

107 As in Meiolania and Sunflashemys, the canalis cavernosus is a large chamber, bean- shaped in section, opening below and lateral to the fenestra ovalis. This morphology appears to be synapomorphic for meiolanoids. In AR18672, the lateral wall of the rear section is formed by the quadrate dorsally and the prootic ventrally. This contact is sutured, unlike the condition in Sunflashemys. AMF18668, a skilfully sectioned braincase (Gaffney 1996) has sutures showing the canalis cavernosus floored by the quadrate posteriorly and the prootic anteriorly (pers. obs.), but in Sunflashemys and some specimens of Meiolania (e.g. AMF57984) the pterygoid floors an anterior section of the canalis cavernosus. In AR18672, the quadrate reaches the pterygoid below the lateral margin of the basisphenoid, approaching the interpterygoid vacuity as in Sunflashemys and Spoochelys from Lightning Ridge. Sutures are fused or unclear in the Lord Howe Island specimens, but bone trabeculae and texture strongly suggest that the ventromedial quadrate extension in meiolaniids may be greater than previously indicated (pers. obs.).

Prootic Ventromedial limits of the prootic are concealed from below by the quadrate and posteromedial process of the pterygoid. The prootic is strongly fused with the processus interfenestralis of the opisthotic and is heavily expanded ventrolaterally, forming the roof of the canalis caroticus internus and of the foramen posterius canalis carotici interni, and providing a thick floor to the cavum labyrinthicum.

The prootic deeply encloses the canalis nervi facialis, and forms the upper half of the posteromedial wall of the canalis cavernosus, in which there is no opening that might be construed as the foramen pro ramo nervi vidiani and no transverse constriction signifying the sinus cavernosus. A probe placed through the fossa acustico-facialis into the canalis nervi facialis emerges posteriorly into the cavum acustico-jugulare.

Basisphenoid The basisphenoid is deep and tilted anterodorsally. The basisphenoid crista bisects the interpterygoid vacuity and is fused to the underlying pterygoid lamina. As in Meiolania, the ‘foramen caroticum basisphenoidale’ is hidden in ventral view by the pterygoid lamina. From this opening, a small sulcus extends forward, incised into the wall of the basisphenoid crista within the interpterygoid vacuity. The carotid canal travels inside the

108 basisphenoid, opening from the sella turcica (rostrum basisphenoidale) above the interpterygoid vacuity. The steeply inclined anterodorsal pathway of the internal carotid artery is typical of meiolaniids and is a feature of Sunflashemys. The foramen nervi abducentis opens from the lateral section of the dorsum sellae, as in Sunflashemys.

Pterygoid The pterygoid forms the floor of the interpterygoid vacuity, the floor of the canalis caroticus internus (rear of the foramen caroticum basisphenoidale) and the floor of the foramen posterius canalis carotici internii. There appears to be a ventral contact between quadrate and pterygoid close to the lateral extremity of the interpterygoid vacuity. In Spoochelys, Sunflashemys and the meiolaniid cf. Warkalania from Riversleigh, the interpterygoid vacuity extends laterally into the medial surface of the pterygoids. In one or two of the Lord Howe Island skulls, there is midline contact of the pterygoids with the basisphenoid crista. Although the contact is fused in the meiolaniid cf. Warkalania, this contact is neither sutured nor fused in Meiolania and the contact is hidden in ventral view in all meiolaniids. In AR18672 and Meiolania, the sagittal passage of the interpterygoid vacuity is floored by pterygoid laminae that join on the midline along the basisphenoid crista but are separated dorsoventrally from the rostrum basisphenoidale. The structure differs significantly from the cryptodiran and eucryptodiran state in which the rear margins of the pterygoid laminae are sutured transversely across the rostrum basisphenoidale.

In the meiolaniid cf Warkalania, the pterygoid merges inextricably with the ventral surface of the basioccipital tubercle and with the exoccipital below the recessus scalae tympani. The sheet-like pterygoid extension across the floor of the basisphenoid is unsutured and the pterygoid wraps around but does not contact the anteroventrolateral surface of the basioccipital: these bone surfaces are separated by an open cavity (the basipterygoid fissure), as in Meiolania.

Basioccipital Basioccipital-pterygoid contact is less devloped than in Meiolania, leaving more of the basioccipital tubercle exposed. A small ventral tubercle is located parasagittally on the basioccipital near the basisphenoid suture. Presumably this is one of a pair, homologous

109 with the subsidiary basioccipital tubercle of the paratype skull of Sunflashemys, in which the tubercle is present on the left side only. The basioccipital condyle is short and massive, with a broad convex articular surface, unlike Meiolania in which the articular surface is weakly concave.

Exoccipital The exoccipital forms the lateral margin of the foramen magnum and as in Sunflashemys, the exoccipital is widely separated from the neck and articular surface of the occipital condyle. The rear wall of the foramen magnum slopes anteroventrally as in Spoochelys, Sunflashemys and Meiolania. In Proganochelys, two foramen nervi hypoglossi open from each exoccipital and are partly confluent with the foramen jugulare anterius, which is very large. The foramen jugulare anterius in the meiolaniid cf. Warkalania is huge, almost the same size as the fenestra ovalis and is concealed in occipital view. The two foramina nervi hypoglossi are located in the suture between exoccipital and basioccipital as in Spoochelys (but unlike Sunflashemys). The foramen jugulare posterius is unformed.

Opisthotic As in Meiolania, the aditus canalis stapedio-temporale is formed in part by the opisthotic, and the foramen stapedio-temporale appears to be formed by opisthotic, quadrate and prootic. Opisthotic contribution to the stapedial canal and foramen is otherwise known only in Proganochelys. Meiolaniids are more derived than Proganochelys but primitive compared to all other turtles in these structures.

In the meiolaniid cf. Warkalania, the stapedial canal is very large and runs perpendicularly, dorsal to the aditus canalis stapedio temporale, opening in the midsection of the otic chamber. This places the foramen stapedio temporale dorsolateral to the fenestra ovalis, unlike the condition in Meiolania in which the foramen has moved anteroventrally on the otic chamber, apparently as a result of the inner inflation of the cavum tympani. In pleurodires, the mandibular artery branches from the stapedial ‘after the latter exits from the skull and enters the fossa temporalis superior’ (Gaffney 1979: 205). In the meiolaniid cf. Warkalania, the margin of the foramen stapedio temporale is divided into two channels, the larger one directed dorsally, and a shallower one anteromedially, evidence of two soft tissue structures diverging outside the otic chamber.

110 Unfortunately, due to poor preservation, it is not possible to determine whether this same condition pertains in the Lightning Ridge taxa.

As in Meiolania, the opisthotic-exoccipital suture runs diagonally across the roof of the cavum acustico-jugulare to the base of the processus interfenestralis, and the fenestra perilymphatica is large.

Canalis nervi facialis While the compendium of information on soft tissue arterial structures in turtles is considerable (McDowell 1961; Albrecht 1967; Schumacher 1973; Gaffney 1975, 1979; Reippel 1980; Brinkman and Nicholls 1991, 1993; Meylan 1996; Jamniczky and Russell 2004; Jamniczky et al. 2006), morphology of the facial nerve is sparsely documented (Gaffney 1979). Separation of the hyomandibular branch (VII) of the facial nerve from the cranioquadrate space (canalis cavernosus) is an important pleurodiran synapomorphy. The facial nerve is separated from the cranioquadrate space in Meiolania, but the condition has been regarded as non-homologous with that of pleurodires because a foramen pro ramo nervi vidiani opening into the canalis cavernosus is reported (Gaffney 1983: 447-448; 1996: 67, 73). Certainly an opening through the medial wall of the canalis cavernosus occurs in five of the nine braincase specimens from Lord Howe Island that have been examined in the course of this study. However, in some of these, the opening is on one side only and when present, the opening is an artefact of breakage, formed in the suture between the basisphenoid and crista pterygoidea (pers. obs.).

In the meiolaniid cf. Warkalania, the structure is unequivocal - the facial nerve is contained in the prootic, separated from the cranioquadrate space by a greater thickness of bone than in Meiolania. There is no opening into the canalis cavernosus and the hyomandibular branch exits into the cavum acustico-jugulare. The condition resembles that of the Australian chelids Emydura macquarii and E. kreffti, in which the ‘hyomandibular branch of the facial nerve (VII) … emerges beside the canalis cavernosus into the cavum acustico-jugulare’ (Gaffney 1979: 123, 131: 40). This is also the condition in Notoemys (Marcelo de la Fuente persn. commun.).

111 The canalis nervi facialis is connected to the sinus cavernosus (cranioquadrate space) in Kayentachelys (Rougier et al. 1995), presumably via the cryptodiran foramen pro ramo nervi vidiani. The facial nerve is separated from the cranioquadrate space in Palaeochersis according to Rougier et al. (1995), but this is subsequently contradicted by Sterli et al. (2007). In Heckerochelys the foramen nervi facialis opens from the ventral surface of the prootic (Sukhanov 2006), separated from the cranioquadrate space and the cavum acustico-jugulare.

Discussion AR18762 represents the best-preserved cranial material for the family Meiolaniidae, apart from specimens of Meiolania from Lord Howe Island, with more of the crucial basicranial features preserved than in the missing type material for Warkalania. The large canalis cavernosus opening well ventral to the fenestra ovalis in AR18762 is a distinctive meiolaniid feature also seen in the new taxa from Lightning Ridge. The quadrate partially floors the canalis cavernosus and appears to reach the basisphenoid, and the prootic forms the roof of the canalis caroticus internus and of the foramen posterius canalis caroticus interni. The canalis nervi facialis is entirely enclosed in the prootic, deeply separated from the canalis cavernosus, and opens into the cavum acustico-jugulare as in Meiolania, Notoemys and certain chelids.

The external carotid canal is floored by the pterygoid in cryptodires, a feature that developed subsequent to pterygoid extension across the inner ear (Gaffney 1979a; Rieppel 1980, 1992; Brinkman and Nicholls 1993). In Notoemys and the Lightning Ridge turtles, the inner ear is open ventrally. In cf Warkalania, the prootic provides a deep floor to the cavum labyrinthicum, as in certain pleurodires, and the pterygoid extends below this. Caudomedial expansion of the pterygoid in the horned turtles developed independently of the cryptodiran condition. In cryptodires (Gaffney et al. 1987), the pterygoid is sutured to the posterolateral section of the basisphenoid and the anterolateral section of the basioccipital. In meiolanoids, contacts are unsutured at precisely the positions where those initial connections formed in the Selmacryptodira (sensu Gaffney et al. 1987). AR18762 shows a number of unsutured contacts between major bone elements; the pterygoid covers less of the basioccipital than in Meiolania; and as in Sunflashemys, there is a small anteromedial subsidiary tubercle on the basioccipital.

112 The foramen jugulare posterius is undeveloped in the Lightning Ridge taxa and the meiolaniid cf Warkalania. In meiolanoids, this feature is developed only in Meiolania, an independent acquisition from the foramen jugulare posterius of turtles such as Araripemys and Kayentachelys, in which this foramen is formed by opisthotic and exoccipital. The meiolaniid cf. Warkalania exhibits a primitive structure of the rear wall of the recessus scalae tympani, with the foramina nervi hypoglossi in the suture between exoccipital and basioccipital.

In Tertiary meiolaniids, including the meiolaniid cf. Warkalania from Riversleigh, the posterolateral limit of the ‘intrapterygoid slit’ conceals a small foramen that may be associated with the facial nerve, perhaps the foramen nervi facialis. In Sunflashemys, this foramen opens in the ventral surface of the basisphenoid near the prootic suture. This is apparently the ‘pit in pterygoid’ in Crossochelys, noted by Simpson (1938: 232: 7A) and interpreted by Gaffney (1983: 443: 60A) as the ‘foramen caroticum basisphenoidale’. It seems more likely that the ‘foramen caroticum basiphenoidale’ of Crossochelys is within the interpterygoid vacuity, hidden in ventral view as in the meiolaniid cf. Warkalania. In Niolamia, as shown by the cast L.1418 at the Australian Museum, this foramen is rear of interpterygoid vacuity (pers. obs.; contra Gaffney 1983), resembling the more primitive condition in the Lightning Ridge taxa.

Crossochelys is reliably provenanced to the Eocene of Chubut. Differences between Crossochelys and Niolamia in basicranial structure and in the dermal skull roof infer taxonomic distinction (contra Gaffney 1996), adding credence to the original claim of Late Cretaceous provenance for Niolamia (Ameghino 1899: 10) and identification of meiolaniid material in the ‘Alamitian’ of Rio Negro (de Broin 1987; de Broin and de La Fuente 1993).

In summary, cranial material of a meiolaniid cf Warkalania from Riversleigh illustrates transitions between Mesozoic forms such as Spoochelys and Sunflashemys, and Tertiary meiolaniids. This new material helps to establish a number of synapomorphies for the meiolanoids - large canalis cavernosus ventral to the fenestra ovalis; pterygoid separated from posterolateral of basisphenoid and anterolateral of basioccipital; and hypoglossal

113 nerve XII between basioccipital and exoccipital. In cf. Warkalania, the cavum tympani is intermediate in size between that of Niolamia and Meiolania, and the cryptodiran processus trochlearis oticum is absent. Features such as prootic involvement in the canalis caroticus internus and foramen posterius canalis carotici interni, and enclosure within the prootic of the facial nerve, separate from the canalis cavernosus, are evidence that the superfamily Meiolanoidea may be more closely related to primitive pleurodiran taxa than to primitive cryptodires.

114

CHAPTER SIX

REDESCRIPTION AND REINTERPRETATION OF THE LIASSIC TURTLE INDOCHELYS SPATULATA DATTA ET AL. 2000 FROM MAHARASHTRA, INDIA

In this chapter, a new description and comparison is presented of Indochelys spatulata Datta et al.2000, an Early Jurassic turtle from the Deccan of India. This is based on direct examination of type material held at the Geological Survey of India in Kolkata. A number of striking features are reported, not previously recognised or documented, relating in particular to carapacial scutes and structure of the anterior plastron.

Indochelys was included in a cladistic analysis for the first time by Sterli (2008), using information gleaned from the descriptive paper (Datta et al. 2000), not from the actual specimen. That analysis placed Indochelys in an unresolved trichotomy with Kayentachelys and Condorchelys from Middle - Upper Jurassic Patagonia.

Indochelys is significant as a Mesozoic record that is closer in space and time to Early Cretaceous Australia than Palaeochersis of South America and Australochelys of South Africa. Indochelys occupied a section of the Pangean landmass that adjoined the ‘west Australian’ section of the supercontinent during the Liassic (about 208 mya; P. M. Datta pers. comm.; Veevers 2001). The Kota Formation that yielded Indochelys is characterized by argillaceous limestone beds producing charophytes, wood and fragmentary insects, ostracodes, teleost fish, lungfish, primitive sauropods and kuehnotheriid (Datta et al. 2000). These diverse assemblages, and the fluviatile and lacustrine freshwater depositions, are comparable in some respects (presence of charophytes, lungfish and primitive sauropods) to those of eastern Australia during the Early Cretaceous.

Indochelys is nearer stratigraphically and geographically to Triassic turtles of the southern hemisphere than to the middle and late Jurassic forms of Europe and North America with which it was initially compared. Indochelys was described as a ‘casichelydian’ cryptodire resembling Glyptops and pleurosternids, at a phyletic level

116 similar to Kayentachelys from (Datta et al. 2000). This diagnosis was based on morphology of the entoplastron, gular scute, presence of mesoplastra and presumed absence of supramarginal scales. More recently, Kayentachelys has been shown to possess cleithra (Joyce 2006), structures that are absent in all known cryptodires, and has been positioned outside the Cryptodira along the stem of the turtle crown (Parham and Hutchison 2003; Sukhanov 2006; Joyce 2007; Sterli and Joyce 2007; Sterli et al 2007; Sterli 2008).

SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Family INDOCHELYIDAE Datta et al. 2000 Genus Indochelys Datta et al. 2000

Indochelys spatulata Datta et al. 2000 Holotype. Geological Survey of India, Kolkata, GSI20380, a near-complete shell.

Locality and horizon. As per Datta et al. 2000.

Revised diagnosis. As for monotypic genus and species: A primitive stem turtle with sutured carapace-plastron connection, irregular neurals expanding posteriorly, large cleithra, long entoplastron with dorsal keel, razor-shaped mesoplastra and mid-plastral fontanelle. Distinguished by conical supramarginal scale adjoining the eighth costal; a very small first costal; diamond-shaped fifth vertebral exactly covering two suprapygals; and very large epiplastral extensions excluding hyoplastron from margin of anterior plastral lobe. Shares with Proterochersis the semicircular first vertebral, very broad vertebrals, elongated pleurals; and with Chelycarapookus very long epiplastra, large semicircular nuchal and small interneural between the eighth and very large ninth neural.

Redescription and comparison The type specimen consists only of articulated carapace and plastron (Figs. 30, 31, 32, 33). Bone surfaces are relatively smooth, finely granular and delicately reticulated. Major openings are reduced by dorsoventral compaction and originally the carapace vault was

117 probably higher than that of Proganochelys (pers. obs.; contra Datta et al. 2000). The carapace is broad anteriorly and narrower posteriorly, displaying the cordeiform shape that is typical of platychelyids. The amorphous mass on the left suggests large areas of bone, some of which may be upwardly displaced bridge material, however peripherals and marginals are problematic and not as described by Datta et al. (2000). The purported ‘hump’ in the carapace over the nuchal region is very slight and not pronounced as in Caribemys, for example. A midline ridge is more strongly developed at the rear of the carapace and is quite ‘peaky’ after neural six. Otherwise, the carapace is weakly depressed along the midline, except for the crista or ‘gable’ on neural three.

Carapace (Figs. 30, 33) Cervical scute The notch at the front of the carapace suggests that originally a large and prominent cervical scute was present.

Vertebrals Details of scute texture and sulci are shown by a scrap of scute material preserved on the front left section of the carapace. Scutes were weakly tuberculate and the margins form deep, regular interlocking ‘zig-zags’, remarkably similar to vertebral-pleural scute edges in Proganochelys (Gaffney 1990: 120: 73). The first vertebral is mushroom or bowl shaped with a curved anterior contour, resembling Proterochersis and NMVP199057 from Inverloch (Victoria). Vertebral scutes are very broad as in Proterochersis, the third is the widest. Unlike Proterochersis and Chelycarapookus, the sulcus between vertebrals III and IV is not confluent with the sulcus between pleurals III and IV. Vertebral V is small and distinctly diamond-shaped, neatly overlying the two suprapygals. In Mongolochelys, vertebral V includes the two rearmost neurals and the ninth costal.

Pleurals On the left side, the rear half of the first, second and third pleurals and the medial section of pleural four are preserved. These are long, narrow and lens- or diamond- shaped, attenuated at each end and rather elevated; there is a resemblance to the elongated pleurals of Proterochersis. Judging by its anterior position and length, the first pleural contacted the first marginal as in Meiolania and platychelyids.

118 Supramarginals Carapace margins are difficult to interpret, however sutures of the second, third and fourth costals extend lateral to the pleurals, suggesting that scutes adjoining the pleurals may be supramarginals, not marginals. Rear of the fourth pleural, abutting the eighth costal, a heavy conical tubercle represents a posterior supramarginal that contacts the lateral corner of the fifth vertebral scute. Sterli et al. (2007) report a similar prominent tubercle, possibly a supramarginal, on each side of the posterior carapace in Palaeochersis. Elevated carapace tubercles are also seen in Platychelys (Bram 1965: 190: 1). Presence of supramarginals in Indochelys has not been documented previously.

Nuchal Datta et al. (2000) describe the nuchal as large and semicircular with a posterior median notch. Nuchal shape is another strong resemblance to Chelycarapookus, however there is no sign of the inflated nuchal fossae that are seen in that taxon and Meiolania.

Neurals The nine neurals are irregular and markedly wider at the front and rear of the series, as in Chelycarapookus, suggesting that as in the Victorian steinkern, the underlying costo- vertebral tunnel was broader anteriorly and posteriorly. The first neural is very large and a small preneural may be present. The second neural is smaller and drum-shaped; the third neural is long and narrow with a rounded midline crest; neural four is narrow and oblong; neural five is wide and hexagonal, broader anteriorly; neural six is barrel shaped; seven is short and wide; eight short and very wide with median crest; nine is hexagonal, very large, wide and boxy. Contact between neurals eight and nine is restricted by a small lens-like element (?interneural), another remarkable resemblance to Chelycarapookus which also has this lens-shaped penultimate ?interneural.

Lateral edges of the neurals correspond with costal proximal margins: neural to costal alignment is primitive, ribs apparently meet the vertebrae in the normal position so that each costal attaches to one neural (as in Palaeochersis; Sterli et al 2007). The exception is costal seven which adjoins neurals seven and eight, as in platychelyids (Notoemys).

119 Costals There are eight costals. The posterior margin of the first costal curves anterolaterally, so the element is acuminate distally as in platychelyids, and this costal is very narrow rostrocaudally and short, only two-thirds as long as costal two and only half the width of costal three. Distal contacts are not as depicted by Datta et al. (2000). The seventh and eighth costals are distinctly shorter, another interesting derivation present in platychelyids. Costal eight is quite deep rostrocaudally.

Peripherals Peripheral structure is hard to interpret due to post-mortem compaction, however it appears that the third peripheral may accommodate rib ends of costals three and four, as in Sunflashemys.

Suprapygals There are two suprapygals, approximately equal in size. Suprapygal one is diamond- shaped with a median crest and paired anterior notches. Suprapygal two is boomerang- shaped and contacts costal eight anterolaterally and the last supramarginal laterally. The acute posterior pygal point is a feature also seen in Notoemys zapatocaensis (Rueda and Gaffney 2005). The pygal is missing, leaving no clues, however the peripheral notch was probably absent.

Plastron (Figs. 31, 32, 33) The plastron is slightly reduced compared to Proganochelys, with a single large central fontanelle (contra Datta et al. 2000; as in Heckerochelys, platychelyids, Otwayemys and Meiolania), the margin of which is formed by hyoplastron, mesoplastron and hypoplastron. The rear plastral lobe is slightly broader than the anterior section, and slightly elongated, and the plastral lobes curve dorsally at the front and rear, moreso than in Chelycarapookus.

Hyoplastron The axillary buttress is very long and tightly curved as in Palaeochersis, Proterochersis and Chelycarapookus. The axillary ‘outgrowths’ described by Datta et al. (2000) are perhaps the result of anterolateral breakage; or the apparent edge between this ‘outgrowth’ and the hyoplastron may represent a scale sulcus. Buttresses are unthickened 120 and undeveloped, however there is a weak but definite angle between the bridge area and the central section of the plastron: the pleurodiran ‘angled bridge’ (Lapparent de Broin 2000). Carapace and plastron may have been suturally connected as there is no evidence of plastral pegs, possibly due to poor preservation. Plastral scute sulci are absent, a similarity to Meiolania which has only gular and intergular scale sulci.

Entoplastron and epiplastron The anterior plastral lobe is complex and carries important information reported here for the first time. The anterior edge is missing, so the original contour is unclear: it is likely to have been transverse. Post-mortem weathering and erosion has stripped the outer surface, fortuitously exposing different densities of ossification within the bones.

The entoplastron is very large and elongate, extending back level with the axillary notch, as in Proganochelys and Kayentachelys, probably completely separating the hyoplastra and reaching the margin of the plastral fontanelle. There is no evidence of the lateral extensions seen in the isolated entoplastron NMVP186048 from Cape Otway, Victoria (described in Chapter Seven), at least not on the ventral surface. The entoplastron flares at the front, indicating that paired gular projections were probably present, completely separating the epiplastra. This is a distinct contrast to the entoplastron of Mongolochelys and more derived forms in which the entoplastron does not reach the anterior plastral margin.

Ridges of very dense bone form midline structures within the entoplastron. Presence of a dorsal entoplastral keel is indicated by a diamond-shaped structure within the main body of the entoplastron and strong parasagittal and sagittal struts within the posterior section. There is no trace of a gular scute on the entoplastron (contra Datta et al. 2000).

The epiplastra contain densely-ossified structures that may have been exposed on the ventral surface of the plastron prior to postmortem erosion. These are the bases of paired cleithra, elements that have not been identified or described previously in Indochelys. Histology of these cleithral bases provides an interesting contrast to those of Kayentachelys, the only other turtle for which such details are documented. In Kayentachelys, the bases overlap the contact between epiplastra and entoplastron, with at least half of the base positioned dorsal to the entoplastron (Joyce 2000: 96-97: 3). The

121 bases in Indochelys appear to be larger and more restricted to the epiplastron. In Kayentachelys, the ventral base is described as an acute triangle, its apex anterior, either fused or sutured to the plastron (Joyce 2006). Of course, the size, structure and contacts of the ascending portions of the cleithra cannot be deduced, however because the subcircular ventral sections are strongly delineated in cancellous and lamellar bone and appear to be larger and more deeply embedded in the epiplastron than those of Kayentachelys (Joyce 2006: 98: 4) and Heckerochelys (Sukhanov 2006: 115: 2), it would appear that cleithra in Indochelys were substantial.

Of further interest are the large paired bones contacting the posterior margins of the epiplastra and lateral edges of the entoplastron. These long acute elements, extending posterior to the axillary notch, prevent exposure of the hyoplastron on the edge of the anterior plastral lobe. The contact between epiplastra and these elements is transverse, corresponding with the gular scute sulcus of Meiolania, for example, but the bones are weakly disarticulated, exposing interdigitated sutures with both epiplastron and hyoplastron, demonstrating that these are supernumerary ‘post-epiplastral’ elements.

Similar smaller plastral elements in Mongolochelys have been interpreted, antithetically, as ‘gastralia’ (Khosatzky 1997) and ‘autapomorphies’ (Sukhanov 2000). The fact that in Mongolochelys, the bones are free and very loosely articulated with entoplastron and hyoplastron suggests may not be homologous with these larger sutured elements in Indochelys. In fact, in shape, position and length, the structures in Indochelys agree more closely with the posterior ‘epiplastral’ processes of Chelycarapookus.

Mesoplastra Mesoplastra are single and large, narrowing towards the midline as shown by Datta et al. (2000), reaching the margin of the plastral fontanelle.

Hyoplastron The hyoplastron is elongated in comparison to that of Proganochelys, resembling Proterochersis, flaring slightly near the inguinal notch, as in Chelycarapookus. The midline sulcus is straight, although slightly sinusoidal near the fontanelle. Bone in the area of the lateral hyoplastral-xiphiplastral suture is thickened, consistent with presence of an ischial attachment or early phase of pelvic fusion, as described in Palaeochersis.

122 Xiphiplastra Xiphiplastra are large; the midline sulcus is straight; and the anal scute is absent. There may be a slight bifurcation of the rear midline, a pleurodire-like condition. Anterolateral margins of the xiphiplastron project forward at the hyoplastral suture, so the suture is M- shaped, an apparently primitive feature also seen in Proganochelys, Kayentachelys and Chelycarapookus.

Discussion As might be expected in a turtle of this vintage, presence of very broad vertebrals, supramarginals, neurals wider anteriorly and posteriorly, cleithra, a long keeled entoplastron and mesoplastra signify a truly ‘Triassic’ type form. So-called cryptodiran features cited by Datta et al. (2000: 107) – ‘ischia articulating to the xiphiplastron, the presence of a cervical scute, the absence of mid-plastral fontanelles, the immovable anterior plastral lobe, the strongly ossified shell, and a possible buttress in the specimen’ are ambiguously preserved and are not cryptodiran synapomorphies.

Indochelys is rediagnosed on the special combination of primitive, transitional and autapomorphic states. Strong reduction of the first costal and the long attenuated pleurals are autapomorphies, peculiar to this taxon. The large ‘post-epiplastral’ bones are also unique. However, if these structures are homologues of the amniote gastralia, they are plesiomorphies, lost in Proganochelys and other turtles, with the possible exception of Mongolochelys. Further investigation seems warranted of homology and evolutionary significance: are they clavicles, gastralia or neomorphs?

Significantly, rather than resembling Kayentachelys and Jurassic pancryptodires or cryptodiromorphs, Indochelys shares derived features with Proterochersis - broad vertebrals, semicircular first vertebral and long pleurals. There are also similarities to platychelyids (including reduced number of supramarginals, two suprapygals, midplastral fontanelle), Chelycarapookus (neural pattern and shape) and Meiolania (absence of plastral scutes).

Indochelys is a Pangean turtle that lived in relative geographical proximity to eastern Australia. Distinctive derivations in Indochelys reinforce the likelihood of phylogenetic

123 affinity between Triassic turtles and terrestrial and freshwater forms of Early Cretaceous Australia.

124

CHAPTER SEVEN

REDESCRIPTION OF THE CASTERTON STEINKERN, CHELYCARAPOOKUS ARCUATUS WARREN 1969, FROM THE ALBIAN OF WESTERN VICTORIA

In March 1915, James S. Macpherson of Casterton presented to the National Museum of Victoria, Melbourne, the fossilized steinkern or internal mold of a small fluviatile turtle from Carapook in western Victoria. Preserved in limonite (bog-iron ore), the specimen was identified as Emydura cf macquariae, the ‘Murray Mud-’ (Chapman 1919: 12) and was thought to be Pleistocene in age.

Fifty years later, Warren (1969) provenanced the specimen to the Early Cretaceous Merino Group, described Chelycarapookus arcuatus, and erected the family Chelycarapookidae, of uncertain suborder. Although at the time meiolaniids were incompletely documented, it was contended that Chelycarapookus was excluded from the Meiolaniidae.

According to Tyler (1979), Chelycarapookus has features that suggest a ‘potential chelid ancestor’. Gaffney (1981, 1991) asserted that the pelvis was probably free, endorsed the unique combination of characters and classed Chelycarapookus as Cryptodira indeterminant. Molnar (1991) noted the unusual fossae in the carapace anterior to the first rib on each side and the longer rib necks at the rear due to the broadened neurals.

Manning and Kofron (1996) pronounced that the steinkern was pleurodiran, while Gaffney et al. (1998) saw affinities with the Asian eucryptodire groups Sinemydidae and . Lapparent de Broin and Molnar (2001)

129 reaffirmed Chelycarapookus as a primitive cryptodire and endorsed the separation from Otwayemys from Cape Otway in Victoria.

In part, this unstable scientific history reflects the fact that steinkerns are ‘notoriously difficult … for systematic comparisons’ (Gaffney et al. 1998: 6). However the holotype preserves carapace scute fragments and details of the anterior visceral surface and plastron that have not been identified or documented previously.

Review of Chelycarapookus is assisted by comparison with Early Cretaceous turtle material from New South Wales and other Victorian locations. Indochelys spatulata Datta et al. 2000 from Maharashtra, India, is of particular significance (Chapter Six). Represented only by carapace and plastron, Indochelys is a Pangean Early Liassic record (P. M. Datta, persn. comm.) in palaeogeographic proximity to eastern Australia. Although described as a primitive cryptodire at a phyletic level similar to Kayentachelys, Indochelys is a ‘Triassic-type’ turtle with no cryptodiran synapomorphies, showing strong similarities to Chelycarapookus in nuchal shape, posterior neurals and plastron. Furthermore, Indochelys shares derived features with Proterochersis, rather than Kayentachelys.

As in previous chapters, comparisons are with Mesozoic stem turtles, basal members of crown groups and Meiolania.

SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996 Family CHELYCARAPOOKIDAE Warren 1969 Genus Chelycarapookus Warren 1969

Chelycarapookus arcuatus Warren 1969 Holotype. NMVP 13160, a steinkern.

130 Locality and horizon. Early Cretaceous Merino Formation (Albian; Dettman 1963); from ‘an ironstone bed 3 ft from surface’ at Carapook near Casterton, western Victoria.

Revised diagnosis. A primitive freshwater turtle, known from a single steinkern preserving some scute and bone material. As in Proganochelys: paired inflated fossae in anterior roof of carapace; costo-vertebral tunnel wide anteriorly and very wide posteriorly. Shares with Proterochersis: very broad vertebrals; pleurals three and four long and elevated; III/IV vertebral scute sulcus confluent with III/IV pleural scute sulcus; long acuminate epiplastra; long entoplastron; axillary buttress tightly curved, reaching anterior of carapace. These latter three features, and the large semicircular nuchal and interneural between expanded neurals eight and nine are also shared with Indochelys. Shares with Platychelys the short first thoracic vertebra and transversely elongate tubercle on front margin of first thoracic rib. Shares with Meiolania: high neural spine of eighth cervical vertebra articulates with circular nubbin on carapace; first thoracic rib reaches peripherals; first and second thoracic ribs strongly coalesced and fused to first costal; second thoracic rib flattened and tilted anteroventrally; eighth and ninth thoracic ribs span broad costovertebral tunnel; tenth dorsal rib reduced; plastral buttresses undeveloped. III/IV scute sulcus lies along costal six; nine broad irregular neurals; eighth and ninth neurals large; wide posterior plastral lobe; plastron entire and midline sulcus straight.

Distinguished from Otwayemys by wider vertebrals, elevated pleurals, wide first neural, larger first thoracic rib, absence of plastral and bridge fontanelles, larger epiplastra and entoplastron; and from the Lightning Ridge taxa by the heavier scute and plastron texture.

Redescription and comparison This redescription is based on examination of the holotype, and a cast, P.13160. A second, more recent cast in brown resin (no curatorial information) shows

131 details of neural spine cavities and thoracic rib attachment points that are not recorded in the older cast.

The degree of doming resembles Proganochelys and the carapace may have been broad at the front and narrower posteriorly as in platychelyids. It is likely that, in contrast to pancryptodires and cryptodires in which the carapace is emarginated anteriorly, the front of the carapace was rounded, extending forward as in Palaeochersis and Proterochersis. Before lithification, the steinkern was slightly compacted and distorted asymmetrically, detaching the distal ends of the second, third and fourth costal ribs on the left side from the peripherals.

Carapace (Figs. 34, 36) Scutes On the right, rugose bony remnants of the third and fourth vertebral scutes, and the third and fourth pleural scutes are preserved. Vertebrals are very broad. Pleurals are elevated and rectangular. Scute sulci are wide and the shallow intervertebral sulcus meets the deep interpleural sulcus, and both pleurals carry a small central boss or nubbin. Not described previously, these scute features agree closely with Proterochersis, distinct from Proganochelys, Kayentachelys and platychelyids. The sulcus between vertebrals three and four traverses the sixth costal, a feature shared with Meiolania and Otwayemys that is also present in platychelyids.

Nuchal The large semicircular nuchal lacks an anterior notch, a similarity to Meiolania.

Costals The first costal is acuminate, with a convex anterior and transverse posterior margin. Costals three and four are the largest, slightly inflected anteromedially, the fifth is transverse and costal bones and rib ends rear of the fifth are inflected progressively posteromedially. There may be nine costals (as per Warren 1969; contra Gaffney 1981). The tenth rib attachment point and a short section of the suture between the eighth and ninth costals appear to be preserved on the rear

132 broken edge of the steinkern. Among primitive turtles, nine costals are known only in Proganochelys, Kayentachelys and Mongolochelys. Meiolania supposedly has eight costals (Gaffney 1996) but the Lord Howe Island material is problematic, sutures are fused and costal elements are fragmented and rare.

Neurals Neurals are irregular, wider than long. Neurals 1 and 2 are very short and broad; neurals 4 and 5 are unclear, but 3, 6 and 7 are square. Neural 8 is broad and somewhat V-shaped, followed by a small diamond-shaped element. Two vertebral neural spine cavities on the midline posterior to this small element confirm the presence of a very large ninth neural. Posterior neural structure is remarkably similar to that of Indochelys.

Visceral carapace surface (Figs. 34, 36) Chelycarapookus is characterized by unusual features of the anterior carapace roof. The nuchal bears a circular tubercle for articulation with the tall neural spine of the eighth cervical vertebra. The tubercle is between distended fossae formed in the nuchal that partly overly the first thoracic ribs heads. These fossae inflate the visceral surface higher than the remainder of the costo-vertebral tunnel. Although described by Warren (1969) and Molnar (1991) as unique, similar fossae are present in Proganochelys and are also present in reduced form in Meiolania (specimens AMF61402 and AMF57984).

In the carapace ceiling on the anterior margin of the first thoracic rib, a shallow transverse concavity widens laterally and suture ridges on the anteroproximal edge of this cavity are recorded on both sides. An anterior tubercle on the first thoracic rib in Meiolania is described as ‘for the articulation of the dorsal process of the scapula’ (Gaffney 1996: 30), and a similar elongated anterior tubercle, again suggested as an articular facet for the scapula unites Platychelys and Notoemys (Rueda and Gaffney 2005). However homology of these structures in all groups is open to question because in Chelycarapookus, in addition to the thoracic rib tubercle, there are weak convexities in the same position as the ‘pit for dorsal scapular process’ in Proganochelys (Gaffney 1990: 125: 77). It seems

133 possible that one of these articulation sites in Chelycarapookus may be for ligamentous attachment of cleithra. The anterior tubercle on the first thoracic rib is absent in Otwayemys but is present in Sunflashemys from Lightning Ridge.

Neural spines of the thoracic vertebrae are recorded in the steinkern as ten deep oval midline cavities, indicating that the sagittal neural blade was undeveloped as in Sunflashemys and Meiolania (see Gaffney 1996: 18: 14). The ‘crowded’ positions of the two anterior vertebral spines suggest that the first thoracic vertebra was very short, a platychelyid feature (Rueda and Gaffney 2005), but this is not definite.

At right-angle to the midline axis, the first thoracic rib is long, slender and blade- like and fully fused with the overlying costal, as in Notoemys. The first thoracic rib resembles Proterochersis (Lapparent de Broin 2000) in being more slender and elongate than the second rib, reaching the peripheral, well behind the tip of the plastral buttress. The first thoracic rib is strongly coalesced with the second thoracic rib which is broad, flattened and tilted anteroventrally. This fusion includes the rib heads, further evidence of the short first thoracic vertebra. Together the ribs form a wide sloping shelf, lying below the level of the other ribs. Spoochelys exhibits this same united rib structure, as does Meiolania. In Otwayemys, the two rib heads are more widely separated and the first thoracic vertebra is longer. In platychelyids, the first thoracic rib is much reduced, the second thoracic rib is horizontal and rib heads are broad and flat. In the steinkern, the ribs are narrower at their point of contact with the carapace roof than in platychelyids.

The specific name ‘arcuatus’ refers to the bowed arch of the costo-vertebral tunnel at the rear of the carapace. The costo-vertebral tunnel is inflated laterally and dorsally at each end of the thoracic series. Broadening of the entire costo- vertebral tunnel unites Platychelys and Notoemys, but Chelycarapookus exhibits the archaic condition seen in Proganochelys in which the tunnel is narrower in the center of the carapace.

134 Chelycarapookus shares with Meiolania the elongation and posteromedial inflection of the eighth and ninth thoracic rib heads, and reduced length of the tenth thoracic rib, which in Meiolania appears to be detached from the carapace (Gaffney 1996). Gaffney’s (1981) contention that a fused pelvis was absent in Chelycarapookus was based in part on a count of eight costal bones which may be incorrect. In fact, the steinkern does not record the section of carapace which would normally bear the iliac suture of a pleurodire, that is the area lateral to the tenth thoracic rib heads.

Plastron (Fig. 35, 36) As in Proganochelys and Meiolania, plastral lobes of Chelycarapookus are horizontal and weakly angled at the bridge. The plastron is unreduced and lacks the mid-line fontanelle seen in Indochelys and platychelyids. There is no evidence of plastral pegs: carapace-plastron connection was sutural. Both buttresses are limited to the peripherals, leaving no trace on the inner costal surface. The axillary buttress which extends far forward to the anterior margin of the carapace, probably finished on the second peripheral, as in macrobaenids such as Judithemys (Parham and Hutchison 2003) and primitive eucryptodires. However in the degree of elongation and tighter curvature of the buttress, Chelycarapookus is more similar to Palaeochersis and Proterochersis.

Entoplastron, epiplastra and hyoplastron Although the front of the anterior plastral lobe is missing, significant details are preserved. The axillary buttress is long and tightly curved, and the bone is only slightly thickened and contoured dorsoventrally (i.e. the buttress was undeveloped).

Lying partly above the hyoplastron as in Meiolania, the entoplastron divides the hyoplastron to a point almost level with the rear limit of the axillary notch. The steinkern records acuminate epiplastra extending along the lateral edge of the hyoplastron. These are similar although not as large as the epiplastral supernumerary elements of Indochelys (pers. obs.) strongly suggesting that cleithra were present.

135 While it cannot be referred with certainty to Chelycarapookus, NMVP186048, an isolated entoplastron from Cape Otway (Victoria) adds credence to this interpretation of plastral features in Chelycarapookus. Although a small entoplastron is figured for Otwayemys (Gaffney et al. 1988: 14: 10), NMVP186048 is assigned to Otwayemys by the same authors, perhaps erroneously. Morphology of NMVP186048 is archaic - an elongate cruciform entoplastron that probably extended to the front edge of the plastron, with strong posterolateral processes (pers. obs.). The rear section closely resembles that of Chelycarapookus and the dorsal keel is long as in Meiolania. The gular scute pattern resembles Proterochersis and intergulars cover more than one third of the surface. Moreover there are small paired anterior projections like the two gular points of Proterochersis and cavities in the anteromedial surface that may indicate cleithral bases.

Mesoplastra appear to be absent in Chelycarapookus and the midline hyo- hypoplastral suture is transverse.

Hypoplastron and xiphiplastron The manner of pelvic attachment (sutured, ligamentous or otherwise) is unclear but the anterolateral section of the xiphiplastron was thickened on the dorsal surface and the hypoplastron flares at this point, features also seen in Indochelys (pers. obs.). Based on curvature and continuation of broken surfaces, the posterior plastral lobe may have been broader than the anterior lobe. The inguinal buttress is short and apparently finishes level with the fifth costal as in Otwayemys and Meiolania. A remnant of xiphiplastral bone is preserved, showing a strong ornamentation of broad irregular ridges.

Discussion Chelycarapookus exhibits distinctive attributes that are variably developed in a number of primitive southern hemisphere turtles. Certain features are shared with Proterochersis – notably the long tightly-curved axillary buttress, large semicircular nuchal, nine neurals expanded at the front and rear of the series,

136 very wide vertebral scutes, narrow elongate pleurals and confluence of the III/IV vertebral sulcus with the III/IV pleural sulcus.

A sister-group relationship with the horned turtles is strongly supported. Chelycarapookus and Meiolania share the nuchal nubbin, coalition of first and second thoracic ribs and reduction of the tenth thoracic ribs. Significantly, both groups display the thoracic rib tubercle that is diagnostic for platychelyids. As a point of interest here, Meiolania also shares with platychelyids the wide first thoracic vertebra with a concave anterior articulation.

Differences between Chelycarapookus and Otwayemys are well documented (Gaffney et al. 1998; Lapparent de Broin and Molnar 2001) and further distinctions are evident in morphology of anterior neurals, epiplastra, entoplastron, xiphiplastron, scute form and texture. Basically a shell taxon with assigned associated elements, Otwayemys is tentatively aligned with the meiolaniids, currently positioned as a primitive cryptodire (Hirayama et al. 2000; Gaffney et al. 2007) but affinities remain unclear (see Chapter Nine).

Presence or otherwise of the fused pelvis in Chelycarapookus is not determinable, however the short tenth thoracic ribs (also in Meiolania) may represent initial stages of the pleurodiran pelvic condition. Chelycarapookus is united with the Lightning Ridge turtles by a number of derived features, but separated from them on differences in scute texture and plastron ornamentation.

Chelycarapookus is a primitive fluviatile turtle sharing attributes with Proterochersis, platychelyids, primitive land turtles from Lightning Ridge and the meiolaniids. The mosaic of distinctive features that is variably developed across these primitive taxa suggests broad radiations of meiolaniid-like pleurodiromorph turtles across southern Pangea.

137

CHAPTER EIGHT

AUSTRALIA’S OLDEST CHELID PLEURODIRES FROM LIGHTNING RIDGE, NEW SOUTH WALES - FIRST EVIDENCE OF CHELIDS FROM MESOZOIC NEAR-POLAR AUSTRALIA

A handful of opalised fossil specimens from Lightning Ridge, New South Wales, represents Australia’s oldest chelid pleurodires, first evidence of this group from Mesozoic Australia. Identified as Chelidae gen. et sp. indet., this record is around 50 my older than the previous oldest for Australian chelids and demonstrates that during the Albian, chelids inhabited high-latitude regions (~60-70oS). The Lightning Ridge material is near-contemporaneous with the oldest known chelids from Patagonia, suggesting that the evolutionary history of chelids in Australia is as prolonged and diverse as in South America.

Occurrence of chelids in the Albian of South America and Australia supports a monophyletic origin for the group in southern high-latitude Gondwana, long before separation of the South American and Antarctica/Australian sectors of the supercontinent. Chelids are sister-clade to Pelomedusoides in the nanorder Eupleurodira (Gaffney et al. 2006). The diversity of chelids and pelomedusoids in the earliest Cretaceous of South America suggests a basal eupleurodiran divergence in the Late Jurassic (Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001) and that ‘a significant amount of the earlier record is missing‘ (Gaffney et al. 2006: 652).

All Australian fossil chelids are assigned to recent taxa and the number of extant species is unclear - about 15 (Burbridge et al. 1974; Gaffney 1977, 1991); or up to 25 (Cogger 1975; Cann 1998). Small turtles of exceptional diversity, chelids dominate present-day Australian turtle faunas and nearly every major water catchment has its own endemic form (ibid., 1998). Living taxa are of particular interest for morphologic, biogeographic and phylogenetic reasons, as are fossil groups. Despite their

141 predominance, chelid evolutionary history in Australia is poorly understood and the fossil record is flimsy.

Chelids exhibit plesiomorphic cranial features with few derived characters to provide clues to systematic status. No known derived skull characters distinguish the short- necked forms Elseya and Emydura (White 1997). Chelid relies principally on skull features as the shell has been considered too variable within chelid lineages, and for the same reason, scute features which are used to identify modern taxa are of limited phylogenetic value for fossil groups (Gaffney 1979c). Nonetheless, shell features are used diagnostically by a number of workers (White and Archer 1994; Lapparent de Broin and de la Fuente 2001; Lapparent de Broin and Molnar 2001) and Thomson et al. (1997) give postcranial characters for diagnosing short-necked chelids to genus. Chelids are characterised by extensive lateral cheek emargination, absence of quadratojugal and mesoplastra, reduction or absence of neural bones and a cervical vertebral pattern of (2( (3( (4( (5) )6) )7( (8) (Gaffney 1991). The long-necked sp. (subfamily Chelinae Gray 1825) are diagnosed on fusion of the frontal bones, absence of temporal roofing and absence of parietal-squamosal contact (Gaffney 1977; White 1997).

Lack of good crania and articulated material in the fossil record is a critical factor (Gaffney 1981; Molnar 1991), as is lack of descriptive work for living forms. No skulls are available for Australian chelids until the Miocene (Riversleigh), or for South American taxa before the Upper Cretaceous. Yaminuechelys gasparinii Lapparent de Broin and de la Fuente 2001 of the sub-group, is the oldest chelid skull (Upper Campanian-Lower Maastrichtian, Patagonia). Fragments of small chelids cf. Prochelidella argentinae Lapparent de Broin and de la Fuente 2001 are known from the Lower and Late Albian of Patagonia. Multiple taxa in Late Cretaceous, Tertiary and sites in South America attest to extensive diversifications in southern Gondwana (de Broin 1971, 1987, 1991; de Broin and de la Fuente 1993; de la Fuente and de Broin 1997; de la Fuente 1999; Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001).

The previous earliest Australian record for chelids is the Eocene of Redbank Plains, Queensland (Lapparent de Broin and Molnar 2001), where chelids are represented by

142 good carapace material but no crania or other elements. About ten taxa are present, assigned to the extant genera Chelodina and Emydura. This high level of diversity by the Eocene attests to the great antiquity of the lineage in Australia.

References to Australian chelid records and phylogenetic studies of chelids and pleurodires include Burbridge et al. (1974), Gaffney (1977, 1979, 1988), Burke et al. (1983), Gaffney et al. (1989), White (1997) and Georges et al. (1998).

Most of the specimens described here were donated to the Australian Opal Centre, Lightning Ridge, under the Cultural Gifts Program. Donors were Marcel Miltenburg, Henk Godthelp, Graeme and Christine Thomson, Rob and Debbie Brogan. One specimen was purchased in 1985 by the Australian Museum, Sydney, as part of the Galman Collection; two were collected by the author from tailing heaps at the Coocoran.

SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Suborder CASICHELYDIA Gaffney 1975 Infraorder PLEURODIRA Cope 1864 Nanorder EUPLEURODIRA Gaffney and Meylan 1988 Hyperfamily CHELOIDES Gray 1825 Family CHELIDAE Gray 1825

Chelidae gen. et sp. indet. (Figs. 37A, E, F; 38A-I) Material. LRF1308 and LRF1312, carapace and plastron fragments, and AMF121611, left ilium, from Emu’s Field, Coocoran; AMF68268, cervical vertebra, from an unknown location at Lightning Ridge; LRF458, partial cervical centrum, from Steen’s Rush, Coocoran; LRF733, procoelous caudal vertebra from Holden’s Field.

Horizon and age. Finch Claystone Facies of the Wallangulla Sandstone Member of the Griman Creek Formation, Lightning Ridge. Early - middle Albian (Exon and Senior 1976; Morgan 1984; Burger 1986, 1995); middle - late Albian (Dettman et al. 1992).

143 Description Carapace and xiphiplastron fragments (Fig. 37) LRF1308 is an indeterminate carapace section, broken into several cojoining pieces, possibly elements of posterior costals and peripherals. Broad shallow scute sulci are evident. The dorsal surface exhibits a pattern of irregular wavey linear incisions, some forming small polygons enclosing groups of micro-fossae. Although it is neither uniformly distributed nor geometrically regular, the polygonal decoration is typical of chelids from South America (Lapparent de Broin and de la Fuente 2001; de la Fuente 2003) and Australia (Gafffney 1981; Lapparent de Broin and Molnar 2001). The partial left xiphiplastron (LRF1312) is markedly elongate, indicating that the rear plastral lobes were everted (bifid), and the ischial scar is large, triangular and extends into the horn-shaped xiphiplastral point. These are typical chelid features, seen also in Prochelidella portezuelae de la Fuente 2003, Bonapartemys bajobarrealis and Lomalatachelys neuquina Lapparent de Broin and de la Fuente 2001 from Late Cretaceous Patagonia. Ornamentation of the ventral xiphiplastral surface is poorly defined and extremely delicate, again consisting of incised reticulations enclosing pin- point sulci. In platychelyids, pelomedusoids and (Hirayama et al. 2000), the rear plastral lobe is bifid, but the xiphiplastra are not horn-shaped as in chelids.

Fourth cervical vertebra (Fig. 38) AMF68268, a fourth cervical vertebra, is poorly preserved and encased in a peculiar coating of ‘crockery’ potch which obscures surface details. The specimen is very elongate, and biconvex, with a low neural arch. Prezygapophyses are well separated with articulation facets oriented dorsomedially, and postzygapophyses are closely apposed but not cojoined. Transverse processes are robust and set midway along the centrum, which is strongly pinched ventrally. Central condyles are 0-shaped and continuous with a low, rounded ventral keel that is slightly deeper posteriorly. Neural arch structure resembles Elseya but the elongation and lateral compression suggest a long-necked chelid cf. Chelodina.

144 Cervical centrum (Fig.38) LRFR458 is a partial eighth cervical centrum, missing the anterior central condyle, which was triangular and continuous with the sharp ventral keel. LRF458 is notable for the pronounced lateral compression and tall, very narrow posterior facet. This specimen resembles the eighth cervical of Prochelidella from Late -Early Coniacian Neuquen Province, Argentina (de la Fuente 2003: 564: 7), and a partial eighth cervical centrum from Al Abra (Rio Negro; Cretaceous) that is assigned to the group (de Broin and de la Fuente 1993: 62: 6a, b). There is also clear similarity to Elseya.

Caudal vertebra (Fig. 38) LRF733, a small caudal vertebra with long robust chevron keel, is one of the very rare procoelous turtle caudals in the Lightning Ridge assemblage, and identification as chelid is tentative.

Ilium (Fig.38) AMF121611, an isolated right ilium, is weathered and eroded, almost identical in overall morphology with Elseya. The proximal attachment is broadly flared, concave, oval in outline and slightly acuminate anteromedially, and the basal section near the acetabular articulation is subtriangular.

Family CHELIDAE Gray 1825

Chelidae gen. et sp. indet. (Fig. 38B-D) Material. LRFR459, peripheral from Dooley’s Field, Coocoran.

Horizon and age. Finch Claystone Facies of the Wallangulla Sandstone Member of the Griman Creek Formation, Lightning Ridge. Early - middle Albian (Exon and Senior 1976; Morgan 1984; Burger 1986, 1995); middle - late Albian (Dettman et al. 1992).

145 Description Peripheral (Fig. 37) LRFR459 is a ?fourth peripheral with a sutured margin for connection with the plastron and two costal rib fossae. The dorsomedial section is a semicircular plate that was loosely attached to the adjacent costals. This basic morphology resembles bridge peripherals of Notoemys laticentralis and Bonapartemys from Argentina and Chelodina sp. from Redbank Plains (Lapparent de Broin and Molnar 2001). The dorsal gutter is narrow and a thin sheet of epidermal scute material with a weakly granular surface texture is preserved. The specimen resembles anterior bridge peripherals of Sunflashemys, but these do not have two rib attachment fossae or the semicircular dorsomedial flange. In LRF459, the bone exhibits a distinctive, heavily convoluted ‘ropey’ surface and internal histology (microvermiculation), suggesting a separate taxon from LRF1308 and LRF1312.

Discussion The Lightning Ridge material is pleurodiran and is referred to Chelidae on resemblance to forms such as Prochelidella, Chelus, Elseya and Chelodina. Structure of the sutured ilium/carapace attachment, shape of the ischial scar and xiphiplastral points are distinctively chelid-like, as is the ornamentation of polygons enclosing micro-fossae. The peripheral bone displays typical chelid features and cervical vertebrae agree closely with chelid specimens from South America and Australia. Given differences in bone microstructure, at least two taxa are represented, however because skull material (preferrably articulated) is needed for taxonomic distinctions, the material is diagnosed as Chelidae gen. et sp. indet., pending recovery of further specimens.

While AMF68268 represents a turtle of ~300 mm carapace length, the other material indicates much smaller individuals. Small size in chelids is not uncommon, seen in Pseudemydura umbrina Siebenrock 1901 (Burbridge 1984) and the Patagonian chelids (Prochelidella sp.). White (1997) speculates that the tiny chelids of Riversleigh, Queensland, may indicate shallow or still water habitats. Depositional details are unavailable other than for the Miltenburg specimens which were retrieved from a major palaeochannel accumulation, in association with plant debris, viviparid

146 gastropods (Albianopalin sp. and Melanoides sp.), and elements of crayfish, actinopterygians and plesiosaurs. The location also produced a diminutive hypsilophodontid dentary and articulated and associated hypsilophodontid material.

The Lightning Ridge chelids occur at higher palaeolatitude than any other record for the group. Temperatures effect incubation rates and growth of hatchlings in reptiles and duration period of the cold season is as critical as actual temperatures, not only for incubation but for hatchling attributes and survival of juveniles (Booth 1999). Modern chelids cannot tolerate temperatures below ~10oC (Lapparent de Broin and Molnar 2001) and their distribution is climatically restricted. For breeding, a yearly seasonal cycle with at least a short period of high temperatures (higher than for birds or mammals), or a longer period of more moderate temperatures is required. Pleurodires are not as well adapted to cold conditions as certain cryptodires, although chelids hibernate and aestivate in deep mud. It is unclear whether Early Cretaceous chelids were more cold-adapted than their extant descendents, which survive winters of 10oC minimum, or even colder (ibid., 2001) at their present southernmost distribution limit in southern Australia.

The previous disparity between Australian and South American records led to the suggestion that geographic barriers and the polar climate prevented east-west dispersal across Gondwana during the Early Cretaceous. The Lightning Ridge material is too fragmentary to determine whether ‘Occidental‘ and ‘Oriental‘ chelids (as per Lapparent de Broin and Molnar 2001) had emerged by the Albian. No Australian chelids are known in South America and at this stage it is unclear if the Lightning Ridge specimens represent new taxa or taxa that occur elsewhere. In this context, similarities to South American forms such as Prochelidella and Chelus are intriguing and invite more detailed comparison.

In summary, Lightning Ridge has produced the only pre-Eocene evidence of chelid pleurodires outside South America and the first record of the group from Mesozoic Australia. At higher palaeolatitude than chelid records from the Albian of Patagonia and representing the most southern known occurrence for the group, the Lightning Ridge material demonstrates that chelids were widely dispersed across the polar supercontinent by the Albian and that their evolutionary history in both Australia and

147 South America was protracted and multiform. Occurrence at 100-110 mya of at least two chelid taxa in Australia, and several taxa in South America supports the hypothesis of a monophyletic origin for chelids in southern Gondwana, possibly in the Late Jurassic or even earlier. It is unclear at present if the Lightning Ridge chelids represent new groups or South American clades previously unknown in Australia, and generic diagnosis of the material awaits discovery of further fossil specimens. The high degree of endemism and palaeogeographic isolation of Early Cretaceous Australian biotas strongly suggests that fossil data will confirm ancient and vicariant radiations of chelids in Australia and South America.

148

kCHAPTER NINE

PHYLOGENETIC ANALYSIS – NON-MARINE TURTLES OF EARLY CRETACEOUS AUSTRALIA, AND RELATIONSHIPS OF THE SUPERFAMILY MEIOLANOIDEA

In previous chapters, three new non-marine turtles and chelid pleurodire specimens from Lightning Ridge, New South Wales, were described, and new data was presented for fossil turtles from Victoria, Queensland, South America and India. A cladistic analysis incorporating these taxa, stem turtles, and basal pleurodires and cryptodires is discussed in this chapter.

It is generally thought that meiolaniids and Chelycarapookus and Otwayemys from Victoria are related to Jurassic and Cretaceous Laurasian eucryptodires from Asia and North America (Gaffney 1996, 1998; Lapparent de Broin and Molnar 2001; Gaffney et al. 2007). Phylogenetic investigations frequently locate the meiolaniids among primitive cryptodiran groups such as plesiochelyids, pleurosternids, Kallokibotion and Xinjiangchelys. Meiolaniids are usually compared with forms such as Dracochelys bicuspis Gaffney and Ye 1982, Ordosemys leios Brinkman and Peng 1993 and Hangaiemys hobdurensis Sukhanov and Narmandakh 1974, primitive eucryptodires that are loosely grouped as the ‘Sinemydidae/Macrobaenidae’ (Gaffney 1996; Gaffney et al. 1998; Brinkman and Wu 1999; Sukhanov 2000; Gaffney et al. 2007). In the original description and analysis of Otwayemys by Gaffney et al. (1998), this Victorian turtle was united with this predominantly Asian fraternity on features such as absence of mesoplastra, and the biconvex eighth and presumed biconcave ?fifth cervical. Otwayemys and meiolaniids were precariously linked in some of the trees in that analysis, although no unique synapomorphies common to these taxa were found.

In other analyses, meiolaniids and Otwayemys are postioned slightly lower on the cladogram, with Asian forms such as Mongolochelys and the Sinochelyidae.

151 Hirayama et al. (2000) suggest an origin for the group among primitive cryptodires originating in the Early or mid-Jurassic, pre-dating the breakup of Pangea. More recently, Meiolania is placed among diverse Early Mesozoic stem turtles from the northern hemisphere (Joyce et al. 2004; Joyce 2007; Sterli 2008).

The analysis by Gaffney et al. (2007) of relationships of Chubutemys (Fig. 40) from the Albian of Patagonia, reinstated a fragile connection between Otwayemys, meiolaniids and the Laurasian taxa, on the biconvex fourth and eighth cervicals. In the preferred tree, the meiolaniids in tandem with Chubutemys and Otwayemys were reunited with basal eucryptodires outside the living Cryptodira. It was found that the only character linking Otwayemys and the meiolaniids was position of the transverse processes of the cervicals in the middle of the centrum; and only one unequivocal character united Chubutemys and the meiolaniids: prefrontal- postorbital contact preventing orbital exposure of the frontal. Sterli et al. (2007) drew a similar result, placing meiolaniids as sister taxon to Cryptodira (Centrocryptodira sensu Gaffney and Meylan 1988).

According to conventional arguments, derived features of of the dermal roof and basicranium are homologous in meiolaniids and northern hemisphere eucryptodires. In relation to the dermal roof, it is suggested that the neck frill and skull horns of meiolaniids developed from the advanced condition in which deep emargination exposes most of the otic chamber in dorsal view (Brinkman and Wu 1999; Gaffney 1996; Gaffney et al. 2007). Apart from the fact that temporal bones are fused in Meiolania (Gaffney 1983), making interpretation of elements and contacts unreliable, this proposition is questionable simply in terms of parsimony. No turtle with an emarginated skull has heavy scales on the rear temporal margin. If meiolaniids redeveloped the skull roof subsequent to emargination, it might be assumed that bony scales on the temporal edge would be absent. From another perspective, meiolaniid horns and neck frill prevented retraction of the head below the carapace. Skull emargination develops after the carapace takes over the function of protecting the head. Skull roofing redevelops when neck retractibility is secondarily lost as in marine turtles (Simpson 1938; Gaffney 1979). If this was the sequence in meiolaniids, temporal emargination evolved along with neck

152 retractibility, then skull horns developed to protect the head, which prevented withdrawal of the head below the carapace - an implausible progression.

The extent to which the massive horns and neck frill are autapomorphic in Tertiary meiolaniids is unclear, but the meiolaniid dermatocranium is not secondarily developed from the emarginated eucryptodiran or daiocryptodiran condition. Supratemporal horns are a feature of parieasaurs, a likely turtle outgroup, and meiolaniids in the Late Cretaceous of Patagonia had horns, as did meiolaniids in the Miocene of Riversleigh, Queensland. Horns are not known in the Lightning Ridge taxa, maybe because turtle horns have not been found so far at Lightning Ridge, or perhaps because the horns developed ontogenically and the preserved skulls represent sub-adult individuals. The postcranial skeleton of Spoochelys is less sturdy and robust than that of Meiolania, and meiolaniid metatarsals from Lake Pitikanta (Miocene, Etadunna Formation) are more generalized and rather more ‘lightweight’ than in Meiolania (see Gaffney 1996: 102-103 : 81, 82). The Lake Pitikanta specimens are meager but there is an inference that the graviportal proportions of limb bones which typify Pleistocene meiolaniids is relatively recent, correlated with the heavy cranial outgrowths and cantilevered neck frill. Nonetheless, the box-like skull, supratemporal horns, cranial bosses and shelves are Triassic features, and the skull of Spoochelys is fully roofed and retains the postparietal and supratemporal.

Bony skull armour is not incompatible with a predominantly lateral mode of neck movement. Even if the head could not be withdrawn below the carapace, transverse orientation of the horns in Tertiary meiolaniids is one of many signals that neck movement was basically sideways. Atlantal fusion is rare in turtles, consistently associated with rapid and powerful lateral neck movement. Atlantal fusion in Meiolania in combination with the primitive atlantal ribs, narrow atlantal centrum and other ‘pleurodire-like’ derivations in the cervical series, suggests that atlantal fusion is a primitive modification correlated with lateral flexion.

As for the all-important basicranium, the Lightning Ridge taxa lack the processus trochlearis oticum and enclosed canalis caroticus internus of eucryptodires, while exhibiting a peculiar combination of basicranial apomorphies that are typical of

153 meiolaniids and pleurodires. The wide interpterygoid vacuity that is present in Spoochelys is the homologue of the meiolaniid ‘intrapterygoid slit’ (of Gaffney et al. 2007) and the basicranium resembles that of Notoemys - the prootic is exposed and cavum labyrinthicum, cavum acustico-jugulare and recessus scalae tympani are unfloored. The interpterygoid vacuity is not the foramen posterius canalis caroticus laterale of extinct eucryptodires [see below, characters 31 and 58].

The Lightning Ridge taxa span at least some of the structural territory that might be expected in stem turtles that are closer to pleurodiran forms than to cryptodires. Providing forceful evidence of a ‘pleurodiran’ capability, cervical morphology in Spoochelys, Sunflashemys and Meiolania displays a multiplicity of derived features associated with lateral neck movement. In the Lightning Ridge taxa, the deep ventral keel on central condyles and tapered lower margin of posterior cotyles promotes lateral flexure and prevents vertical movement between adjacent vertebrae. Shallow excavations in the neural arch below the postzygapophyses accommodate the prezygapophyses of the succeeding vertebra as the neck is flexed sideways. In cryptodires, because zygapophyseal articulations are hinged vertically, the neural fossae extend both above and below the level of the postzygapophyseal facets (pers. obs.). Apart from the biconvex fourth, the central articulation pattern is chelid-like and in posterior cervicals, central facets are tall and the elevated neural arches place the postzygapophyseal facets well behind the centrum. In these taxa and meiolaniids, transverse processes are located in the middle of centrum and are very wide, a pleurodiran feature associated with enlargement of the M. testo- cervicalis lateralis of the longissimus system (Hoffstetter and Gasc 1969), related to lateral movement. The large cervical ribs of Opalania and Meiolania did not hinder or prevent lateral movement. In Meiolania, the ribs were attached ligamentously and are concave posteriorly to accommodate the parapophyses of the following vertebra on the inside curve during lateral flexion (pers. obs.; Fig 41). The medial parapophyseal surfaces are continuous with the central facets, increasing the arc of lateral movement, and reduction of the seventh cervical ribs facilitates lateral movement close to the carapace, in conjunction with the horizontal pivot formed by the cervico-thoracic joint.

154 This derived cervical morphology is not necessarily an aquatic adaptation or an indication of predatory ‘strike’ capacity. The cervical vertebrae are very short in the Lightning Ridge taxa and the anterior extension of the carapace which is so pronounced in Proterochersis and certain southern hemisphere groups, including shell specimens from Early Cretaceous Victoria, strongly suggests that lateral neck flexure was initially a defensive (‘retractile’) rather than predatory (‘extensory’) specialization. Central articulations are concavo-convex in all known pleurodires and it may be that once the sub-carapacial thoracic and sacral vertebrae are immobilized, concavo-convex vertebral articulations are fundamental to fast lateral movement of the adjoining axial series. A central condyle commonly develops when a laterally-moving section of the vertebral column opposes a fixed vertebra. This may explain why the posterior articulation of the eighth cervical vertebra is consistently a condyle in pleurodires, as in Spoochelys, Meiolania and probably Opalania. The same morphometric principle seems to apply to first caudals of tail scudders or swingers (crocodiles and ankylosaurs), and to the opisthocoelous first caudal vertebra of the Lightning Ridge turtles and Meiolania.

The hypothesis that the horned turtles are a long-surviving relic group of ancestral proto-pleurodirans or pleurodiromorphs is based on a complex series of derived cranial and postcranial features common to the Lightning Ridge turtles, meiolaniids, Proterochersis, primitive southern hemisphere groups including the australochelyids, and pleurodires. In the datamatrix used in this analysis, almost one-fifth of derived character states are shared by the Australian taxa, meiolaniids and platychelyids; and many of these and other apomorphies are also shared with Proterochersis.

Although homology of the pelvis-shell connection in Palaeochersis is questioned (Marcelo de la Fuente pers. commun.), some workers maintain that Palaeochersis is proto-pleurodiran on the basis of partial pelvic fusion (Lapparent de Broin 2000; Lapparent de Broin et al. 2004; France de Lapparent de Broin pers. commun.). Others have argued that pelvic fusion in Palaeochersis infers homoplasic development of this condition in pleurodires, a scenario that expels Proterochersis from the Pleurodira (Rougier et al. 1995; Joyce 2007). Contending that Palaeochersis has no known skull or neck characters in common with

155 panpleurodires, Sterli et al. (2007) ran a cladistic analysis with Palaeochersis constrained within Panpleurodira, the result of which was 29 steps longer than their two most parsimonious trees. Even so, these authors readily acknowledge that new information on Palaeochersis, basal testudinates and panpleurodirans could alter phylogenetic scenarios. According to their favoured analysis, Proterochersis and Kayentachelys are basal-most pleurodire and cryptodire respectively, united in the Casichelyidia (of Gaffney 1975) and meiolaniids are sister group to Cryptodira. Gene Gaffney (pers. commun.) suggests that pelvic fusion in Palaeochersis is merely an artefact of poor preservation and in the latest comprehensive analysis, Proterochersis is firmly resolved as a pleurodire – sole known member of Parvorder Minipleurodira, sister taxon to Megapleurodira, comprising platychelyids and all other pleurodires (Gaffney et al. 2006).

The australochelyids are currently diagnosed on ‘wide transverse occipital plane with depressions for neck musculature, and temporal fossa partly occluded by overhanging process of the skull roof’ (Sterli et al. 2007). These same features are seen in Australian Early Cretaceous turtles and Tertiary meiolaniids, although not specifically, to date, in the Lightning Ridge taxa. Cranial specimens from Inverloch Victoria, exhibit large circular concavities in the rear otic chamber (pers. obs.), and the skull roof in Meiolania partly occludes the temporal fossa. The position of the nuchal nubbin of an anterior carapace (NMVP208303) from Inverloch indicates that the shell covered up to five or six cervical vertebrae. A similar extension concealing posterior cervicals is recorded for Palaeochersis (Rougier et al. 1995). Clearly, ‘australochelyid’ features are manifest in a range of southern hemisphere groups that are widely separated in time and space.

The view that most Early Mesozoic forms, including the meiolaniids, are stem turtles (Rougier et al. 1995; Sukhanov 2006; Joyce 2007) requires a late Jurassic origin for the turtle crown; and more recent investigations place the split early in the mid-Jurassic (Danilov and Parham 2008). The proposition that all fossil and extant turtles are crown group members except Proganochelys, Palaeochersis and Australochelys (Gaffney 1996; Gaffney et al. 1998; Gaffney et al. 2007) locates the ‘casichelyidian’ divergence in the late Triassic, prior to emergence of turtles in the

156 fossil record. If Palaeochersis is a proto-pleurodire, then the primary turtle dichotomy may have occurred very much earlier.

Methodology 34 terminal taxa were incorporated in this analysis, including Mesozoic, Tertiary and extant groups, many represented by monospecific taxa. A data set was developed of 125 characters, comprising 65 cranial characters, 24 shell characters and 34 axial, appendicular and podial characters. Primary sources for codings and morphological data for unmodified, modified and new characters are given in the following comparative discussion of morphology, distribution and homoplasy. To avoid polymorphism in the data set, character states for Cryptodira are plesiomorphic states seen in Chelonioidea (following Sterli et al. 2007; Williams 1950; Brinkman and Wu 1999; Joyce 2007). Using maximum parsimony as implemented by PAUP*4.Ob10 (Swofford 2002), all characters were unordered and unweighted. Of the 125 characters, 6 are parsimony uninformative, that is either constant across all taxa or signifying an autapomorphy in one taxon.

Character set Skull and lower jaw 1.Cranial scute sulci (New): 0 = undefined or poorly defined; 1 = strongly incised (Gaffney 1979, 1990, 1996; Sukhanov 2000; Sterli and Joyce 2007). Morphology, distribution and homoplasy: Data is missing for many basal taxa, nonetheless scute sulci are poorly defined primitively, and the deeply incised condition that is primitive for meiolaniids unites in Spoochelys, Niolamia and Crossochelys. Welt-like scute margins are autapomorphic for Meiolania. Deep scute sulci are homoplasic in Mongolochelys.

2. Relationship of cranial scutes and underlying bones (New; Fig. 39): 0 = scute and bone not histologically unified; 1 = scute and bone integrated (Gaffney 1979, 1990, 1996). Morphology, distribution and homoplasy: Cranial ossifications of Spoochelys are remarkable in that bones of the dermatocranium are fused with the skull scutes horizontally, and most of the lateral margins of bones and scutes coincide. Scute

157 and bone are integrated also in Crossochelys, prompting Simpson (1938: 240) to remark that ‘bosses and horns … are outgrowths of the normal cranial elements … [without] trace of any suture between a boss and the underlying bone … continuity of texture and fine bony structure is such that origin by fusion is practically out of the question’. In Meiolania, although lateral bone and scute margins are more loosely correlated than in Spoochelys, bone and scute merge horizontally and there are no specimens of cranial bone indicating that scales have been stripped (Gaffney 1983; pers. obs.). The ossified horn sheath of meiolaniids is not a scute (see below). Scute histology in Palaeochersis is unclear, but the relevant literature contains no report of bone and scute margin alignment in other basal taxa or Mongolochelys (Sukhanov 2000). Data is missing for panpleurodirans. The derived condition is confined to Spoochelys and the Meiolaniidae.

3. Layout of scute pattern (New): 0 = X small, G and D present; 1 = X small and G, D, B, C, H, F, E, J, K and I present; 2 = X large and G, D, B, C, H, E, J, K and I present; 3 = any other pattern or no pattern (Gaffney 1983, 1996; Gaffney et al. 1992; Sukhanov 2000; Sterli and Joyce 2007). Morphology, distribution and homoplasy: The ‘trident’ sulci at the front of scale X, producing paired quadrilateral scales G anteriorly and paired D scales posterolaterally appears to be plesiomorphic, occurring in outgroups such as lepidosaurs and Proganochelys. Character state 1 refers to the typical meiolaniid layout that occurs in Spoochelys, which has the small scale X and scutes B, C, D, E, F, G, H, J and K. The large X scale, large A scale, small Y and Z scales and separation of scales D in Niolamia and Crossochelys are apomorphic. Mongolochelys is differentiated by additional scutes rear of the D scales, uniform size and shape of the scutes and disjunction of scute and bone margins. Tight coordination of scute sulci and bone margins suggests direct development of the synapomorphic meiolaniid pattern (Gaffney et al. 1992; Gaffney 1996) from the primitive condition, not as a secondary acquisition. This pattern unites Spoochelys and the Meiolaniidae (Fig. 39).

4. Premaxilla, midline dorsal process: 0 = present; 1 = absent (Rougier et al. 1995; Hirayama et al. 2000; Joyce 2007; Gaffney et al. 2006; Sterli 2008).

158 Morphology, distribution and homoplasy: Nares are divided by premaxillae in Proganochelys and australochelyids. In meiolaniids, nares are variably divided by premaxillae and nasals. Data is missing for the Lightning Ridge and Victorian taxa. Nares are confluent in other turtles apart from Kallokibotion in which nares are divided by the nasals. This character recognises loss of the premaxilla contribution to the nareal division as a derived condition in turtles other than Proganochelys, australochelyids and meiolaniids.

5. Nasal bones: 0 = present; 1 = absent (Gaffney et al. 1991; Gaffney 1996; Brinkman and Wu 1999; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli 2008).

6. Nasal bones, dorsal exposure: 0 = small to large dorsal exposure; 1 = very large dorsal exposure (Gaffney 1996; Gaffney et al. 1998; Gaffney et al. 2006; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Large nasals as in Proganochelys is the primitive state, and the larger nasals of Meiolania were considered synapomorphic for that group by Gaffney (1996). In this analysis, the ‘very large’ condition in which the nasal extends posteriorly, dorsal to the orbit, is recognized as a unique condition shared by meiolaniids and Palaeochersis (Rougier et al 1995: 856: 1B; Sterli et al. 2007). Nasals are unknown in pleurodires other than chelids (Gaffney et al. 1991), although preserved facial material for primitive members is absent. Nasal bones in Spoochelys are probably reduced. Uniquely large nasals unite Palaeochersis and the meiolaniids.

7. Height of narial aperture: low = 0; level with top of orbit = 1 (Gaffney 1979; Rougier et al. 1995; Gaffney and Kitching 1995; Sterli 2008). Morphology, distribution and homoplasy: In rostral view, the nasal aperture in meiolaniids is higher than the orbit. This salient feature is interpreted here as homologous with the elongated nares of Australochelys (Gaffney and Kitching 1995; Rougier et al. 1995). In all other turtles including Proganochelys and apparently Palaeochersis (Sterli et al. 2007), the nasal aperture finishes ventral to the orbital margin. Condition of the nasal aperture is unknown in Indochelys,

159 Proterochersis and the Lightning Ridge and Victorian taxa. The high narial aperture unites Australochelys and the meiolaniids.

8. Fossa nasalis (internal choanae) (New): 0 = very large, open ventrally; 1 = reduced, open ventrally; 2 = reduced, closed ventrally (Gaffney 1979, 1990; Gaffney and Kitching 1995). Morphology, distribution and homoplasy: The fossal nasalis forms a large subtriangular unfloored cavity divided by the vomer in Proganochelys and australochelyids (Rougier et al. 1995; Sterli et al 2007). Although elements forming the division are unclear, the fossa nasalis in Spoochelys is large, subtriangular and without bony floor. Meiolania is similar, with the fossa nasalis divided by vomer and premaxilla. The fossa is reduced and open ventrally in chelids and pelomedusids including Araripemys. Among other groups covered in this analysis, including Kayentachelys (Sterli and Joyce 2007), the fossa nasalis is strongly reduced and closed ventrally. There appear to be no independent acquisitions in the focus taxa.

9.Narial platform or thickening: 0 = absent; 1 = present (Rougier et al. 1995). Morphology, distribution and homoplasy: The narial platform or bulge is absent in Proganochelys and Spoochelys but this feature of Palaeochersis (Rougier et al. 1995; Sterli et al. 2007: 10: 2C, D) is shared with meiolaniids, particularly Ninjemys. The nasal bulge is unknown in other turtles, but again, morphology in Indochelys, Proterochersis and the Victorian taxa is unclear.

10.Large prefrontal (interorbital) bosses and prominences: 0 = present; 1 = absent (Rougier et al. 1995; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Rougier et al. (1995) and Joyce (2007) score these heavy bony ridges as absent in turtles except Proganochelys, despite the fact that prefrontal bosses and tuberosities are a pronounced feature of meiolaniids (pers. obs.; Gaffney 1983: 405: 30) and a prefrontal swelling is shown in Palaeochersis (Sterli et al. 2007: 10: F). Large prefrontal bosses are primitive and are lost in turtles other than Proganochelys, Palaeochersis and meiolaniids. The bosses are absent in Spoochelys and cranial data is missing for Proterochersis and platychelyids.

160 11.Lacrimal bone: 0 = present; 1 = absent (Gaffney and Kitching 1995; Hirayama et al. 2000; Rougier et al. 1995; Gaffney et al. 2006; Sterli 2008).

12.Lacrimal duct (New): 0 = formed in lacrimal bone; 1 = formed in nasal and maxilla; 2 = lacrimal duct fully closed (Gaffney et al. 1991; Gaffney and Kitching 1995; Rougier et al. 1995; Shaffer et al. 1997; Hirayama et al. 2000; Gaffney et al. 2006; Sterli et al. 2007). Morphology, distribution and homoplasy: Proganochelys and Meiolania possess a trough-like cavity in the anterodorsal surface of the maxilla. In Proganochelys this extends into the lacrimal duct in the lacrimal bone (Gaffney 1990). The so-called ‘nasomaxillary sinus’ of Meiolania is blind, formed dorsally by the nasal (Gaffney 1983; pers. obs.), however unnamed foramina in the floor of the orbit between prefrontal and maxilla (Gaffney 1983: 429: 45) may be homologous with the posterior duct opening of Proganochelys and australochelyids. The inference is that the ‘nasomaxillary sinus’ of meiolaniids is actually a modified form of the lacrimal duct. Lacrimal bone and duct are absent in Kayentachelys (Sterli and Joyce 2007) and the condition is indeterminate in other key basal taxa, including the Lightning Ridge turtles. Absence of the lacrimal duct unites turtles apart from Proganochelys, australochelyids and meiolaniids.

13.Vomer: 0 = paired; 1 = single (Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Joyce 2007; Gaffney et al. 2006; Gaffney et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: The vomer is paired in Proganochelys and australochelyids, but is single in other turtles, including Spoochelys and Meiolania, although primitively very large in Meiolania. Woodward (1901: 177: XVI) reported that certain palatal sutures are preserved in Niolamia, describing a single unusually large vomer, however the ventral view of type skull before restoration shows that the vomers may be paired. Meiolaniids other than Meiolania are scored as ‘?’ for this character. Apart from Proganochelys and australochelyids, paired vomers are otherwise unknown in turtles.

161 14.Medial meeting of prefrontals: 0 = absent; 1 = present (Gaffney et al. 1991; Gaffney 1996; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007; Gaffney et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: In primitive turtles, prefrontals are separated from the midline by frontal-nasal contact, as may be the case in Spoochelys. Morphology is unclear in other Early Cretaceous Australian taxa and unknown in Indochelys, Proterochersis and platychelyids. Medial contact of the prefrontals occurs independently in crown group pleurodires (pelomedusoids) and eucryptodires ( and Ordosemys).

15. Prefrontal-vomer contact: 0 = absent; 1 = present (Gaffney et al. 1991; Rougier et al. 1995; Gaffney 1996, 1998; Brinkman and Wu 1999; Hirayama et al. 2000; Parham and Hutchinson 2003; Joyce 2007; Gaffney et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: Forming the anteromedial wall of the orbit, a descending prefrontal process contacts the palatine in Proganochelys and pleurodires (Gaffney 1975; 1979). Morphology is unclear in australochelyids and Proterochersis. In other turtles, including Heckerochelys and Kayentachelys, prefrontal-vomer contact forms the fissure ethmoidalis. The morphology in the Lightning Ridge taxa is indeterminate. There is prefrontal-vomer contact in Meiolania, but again the condition in Niolamia is equivocal. Posterior nares of Niolamia ‘face backwards rather than downwards, separated by a broad flattened bar which seems to be formed by the premaxillae in front and the vomer behind’ (Woodward 1901: 172). This odd transverse division in the floor of the nasal cavity is unconnected to the roof (pers. obs.) and strongly resembles the pleurodiran condition in which the fossa nasalis opens posteriorly and processes of the prefrontal are absent. Spoochelys and meiolaniids other than Meiolania are therefore scored ‘?’ for this character. Prefrontal-vomer contact unites Heckerochelys, Kayentachelys, Mongolochelys and Kallokibotion with crown group cryptodires.

16.Palatal surface: 0 = palatal teeth on vomer, palatine and pterygoid; 1 = palatal teeth on pterygoid; 2 = palate smooth (Gaffney et al. 1987; Gaffney et al. 1991; Rougier et al. 1995; Shaffer et al. 1997; Joyce 2007; Gaffney et al. 2007; Sterli 2008).

162 Morphology, distribution and homoplasy: Palatal teeth are present on vomer, palatine and pterygoid in Proganochelys and on the pterygoid in Kayentachelys (Gaffney et al. 1987: 290: 1C). Palatal teeth are absent in Palaeochersis and Heckerochelys (Sukhanov 2006). Palate morphology is unknown in Proterochersis and Indochelys, but the palate in Spoochelys and meiolaniids is smooth. Absence of palatal teeth unites turtles apart from Proganochelys and Kayentachelys. Loss of palatal teeth occurred below Panpleurodira.

17.Maxilla (New): 0 = deep below orbit; 1 = narrow below orbit (Gaffney 1979; Gaffney and Kitching 1995; Sukhanov 2000; Lapparent de Broin 2000; Sterli et al. 2007). Morphology, distribution and homoplasy: The maxilla is deep in Proganochelys, Kayentachelys, Mongolochelys and Kallokibotion, but in distinct contrast, the maxilla is very shallow below the orbit in australochelyids and Meiolania. Although not apparent in published figures of Niolamia, this is a striking feature in the cast (L1418). Spoochelys exhibits an intermediate condition and the shallow maxilla is shared by australochelyids and meiolaniids. In the absence of skull material for primitive pleurodires, it is presumed that the shallow maxilla of certain chelids is secondary, possibly correlated with development of cheek emargination; the maxilla is deep in pelomedusoids.

18. Deep cheek flanges formed by jugal and quadratojugal (New): 0 = absent; 1 = present (Gaffney 1979, 1983, 1996, 1998; Shaffer et al. 1997; Hirayama et al. 2000; Sukhanov 2000). Morphology, distribution and homoplasy: A large jugal and absence of cheek emargination is the primitive condition (Proganochelys). The enlarged jugal and quadratojugal form deep cheek flanges in australochelyids and meiolaniids (and parieasaurs; Kordikova 2002). Reduction of the jugal and quadratojugal produces the shallow cheek emargination typical of pleurodires, eucryptodires and cryptodires. Although Spoochelys exhibits a weak degree of cheek emargination, similar to that of Otwayemys, the jugal is very large as in Meiolania and the lower jaw of Opalania shows that cheek flanges were developed. The meiolaniid condition is not secondarily developed from the eucryptodiran state (contra Gaffney 1996; Gaffney et al. 1998; Gaffney et al. 2007). Deep cheek flanges

163 formed by ventral expansion of jugal and quadratojugal unites australochelyids and Meiolaniidae.

19.Frontal contribution to orbit: 0 = absent due to prefrontal-postorbital contact; 1 = present (Gaffney and Meylan 1988; Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Gaffney et al. 2007; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Prefrontal-postorbital contact prevents exposure of the frontal on the orbit in Proganochelys, Palaeochersis, Mongolochelys, certain cryptodires, Spoochelys and Meiolania. The frontal reaches the orbit, separating prefrontal and postorbital in other turtles, including Heckerochelys, Kayentachelys, pleurosternids and pleurodires. The condition is indeterminate in Proterochersis and platychelyids. Frontal contribution to the orbit unites Heckerochelys and Kayentachelys and prefrontal-postorbital contact is regained independently in some cryptodires.

20.Postparietal (New): 0 = present; 1 = absent (Gaffney 1979; Sukhanov 2000; Kordikova 2002; Sterli et al. 2007). Morphology, distribution and homoplasy: Paired postparietals were cautiously identified in Proganochelys (Kordikova 2002: 207: A), a reconstruction very similar to Spoochelys (Figs. 2, 4). Although Gaffney et al. (2006) argue that Kordikova (2003) has inadvertently mistaken cracks for sutures, the postparietal in Spoochelys is sharply delineated by its incised margins and the raised triangular postparietal scute. The postparietal seems to be absent in Palaeochersis, but presence of this element in Spoochelys suggests that the postparietal is primitive for meiolanoids and persists in meiolaniids. It should be emphasized that Gaffney’s (1983: 390: 21) reconstruction of the temporal roof in Meiolania is equivocal because meiolaniids are characterized by fusions of the postorbital area. This is frustrating but of intrinsic interest, for these bones fuse also in Australochelys, although not in more derived turtles (Gaffney and Kitching 1995). There is some evidence that a postparietal may be present in Crossochelys (see below).

21.Supratemporal: 0 = present; 1 = absent (Gaffney and Kitching 1995; Rougier et al. 1995; Hirayama et al. 2000; Sukhanov 2000; Joyce 2007; Sterli and Joyce 2007; Sterli et al. 2007; Sterli 2008).

164 Morphology, distribution and homoplasy: The supratemporal in Spoochelys (Figs. 2, 4) is a rounded element separated from the rear temporal fossa by the squamosal. Spoochelys permits identification of the supratemporal in meiolaniids, evidence supported by morphogenic unity of bone and scale, and conservatism of the scute pattern in these two sister-taxa. The B scale ossification of Meiolania, that is, the external bony sheath that encloses the B horn core, is here identified as the supratemporal. Additional evidence is provided by Proganochelys, in which the supratemporal is a ‘floating’ element that overlies the parietal-squamosal suture. Similarly, the B horn sheath in meiolaniids is a floating element, variably fused to underlying bones: it is fused in Crossochelys (Simpson 1938: 240) and Warkalania (Gaffney 1996), remaining as a separate ossification in Meiolania and some Tertiary meiolaniids. Moreover, as in Proganochelys and Palaeochersis, the supratemporal (horn sheath) of meiolaniids projects dorsally above the other skull bones. Previously, the supratemporal was identified only in Proganochelys and australochelyids (Gaffney and Kitching 1994, 1995; Rougier et al. 1995; Hirayama et al. 2000). The condition in Proterochersis and platychelyids is unknown, but loss of the supratemporal may be synapomorphic for pancryptodires or cryptodiromorphs. Supratemporal horns are a pronounced feature of parieasaurs, a putative turtle outgroup.

22.Supratemporal shape (New): 0 = wider than long; 1 = elongate; 2 = subcircular (Gaffney and Kitching 1995; Rougier et al. 1995). Morphology, distribution and homoplasy: In this analysis, Meiolania is scored as having a supratemporal (the B horn sheath) homologous with that of Spoochelys, subcircular in basal outline and separated from the temporal fossa by the squamosal. Meiolaniids with flattened or shelf-like projections rather than conical horns are scored ‘?’ but quite possibly the supratemporal retains its primitive wide shape in these taxa.

23.Contact of supratemporal with postorbital and quadratojugal (New): 0 = absent; 1 = present (Gaffney 1990; Gaffney and Kitching 1995; Rougier et al. 1995; Kordikova 2002). Morphology, distribution and homoplasy: Among turtles, contacts between the supratemporal and the postorbital and quadratojugal are unique to Spoochelys

165 (Figs. 2, 4). Due to cranial fusions, Gaffney’s (1983: 390: 21) reconstruction of Meiolania is conjectural, however the derived state for this character may be primitive for meiolanoids. Although this character is coded on the assumption that absence of these contacts in Proganochelys is primitive, and that Spoochelys is autapomorphic in this feature, it is noted that a supratemporal-postorbital contact is present in parieasaurs. There are no other occurrences among turtles.

24. Squamosal-parietal contact: 0 = present; 1 = absent (Gaffney 1996; Gaffney et al. 1998; Brinkman and Wu 1999; Joyce 2007; Sterli 2008).

25. Position of squamosal-parietal contact relative to supratemporal (New): 0 = mostly anterior to supratemporal; 1 = mostly posterior to supratemporal (Gaffney 1990; Gaffney and Kitching 1995; Rougier et al. 1995). Morphology, distribution and homoplasy: In primitive taxa, the parietal is briefly sutured to the squamosal anterior to the supratemporal. The parietal of meiolaniids is not unusually small when compared to other forms with a supratemporal but it is unclear whether there is squamosal-parietal contact forward of the supratemporal as in Proganochelys and Palaeochersis. In Spoochelys, the squamosal-parietal suture is apparently behind the supratemporal, which is located more anteriorly and this is the condition presumed here for Meiolania (contra Gaffney 1983). The expanded temporal roof in meiolaniids derives from Triassic morphology, not from an emarginated condition.

26. Squamosal-parietal contact in turtles lacking the supratemporal (New): 0 = extensive; 1 = short or absent (Gaffney 1979; Lapparent de Broin 2000; Sukhanov 2000; Joyce 2007). Morphology, distribution and homoplasy: The extensive parietal-squamosal contact in Kayentachelys, Mongolochelys and Kallokibotion, associated with enlargement of the parietal, is antecedent to disconnection of that contact in primitive Asian eucryptodires such as Dracochelys and Hangaiemys, and paracryptodires. Absence of parietal-squamosal contact occurs in chelids, but data is missing for Proterochersis and platychelyids.

166 27. Supraoccipital exposure on skull roof partly dividing parietals (New): 0 = no; 1 = yes (Gaffney 1979, 1990, 1996, 1998; Sukhanov 2000). Morphology, distribution and homoplasy: Primitively, the supraoccipital is not exposed in dorsal view, as in Spoochelys in which the supraoccipital crest projects anterodorsally but fails to reach the dermal roof. In Crossochelys there appears to be a triangular exposure of the supraoccipital on the skull roof, broadening posteriorly (Simpson 1938: 237: 9). The transverse division suggests this may be two elements – the supraoccipital anteriorly and postparietal at the rear, nevertheless Crossochelys appears to have the derived condition for this character. In Gaffney’s (1983) reconstruction of Meiolania, the supraoccipital does not divide the parietals, but is illustrated as flaring anteriorly, somewhat improbably. The supraoccipital in Mongolochelys is weakly exposed between expanded squamosals and does not intrude between the parietals. Dorsal exposure of the supraoccipital restricted to the midline and variably impinging between the parietals occurs in and primitive Asian eucryptodires. Data is missing for Proterochersis and platychelyids, but Araripemys and chelids have the derived condition, developed further presumably as an apomorphy in Pseudemydura.

28. Supraoccipital crest: 0 = absent; 1 = present (Rougier et al. 1995; Sukhanov 2000; Gaffney et al. 2006; Gaffney et al. 2007; Joyce 2007). Morphology, distribution and homoplasy: Primitive turtles lack the supraoccipital crest, a sagittal blade of bone posterodorsal to the foramen magnum that functions at least in part to lengthen the jaw muscle. The crest is absent in Spoochelys. The supraoccipital crest developed in combination with temporal emargination in some groups (Pleurodira, paracryptodires, primitive eucryptodires); and in combination with extension of the rear temporal roof in others (Tertiary meiolaniids, Mongolochelys, Kallokibotion and Pseudemydura).

29.Vertical curtain of bone partly closes rear temporal fossa: 0 = absent; 1 = present (Rougier et al. 1995; Sterli 2007; Sterli et al. 2007). Morphology, distribution and homoplasy: A bony wall overhanging the temporal fossa is a diagnostic feature for Australochelyidae (Sterli et al. 2007). In Australochelys this curtain of bone is smooth, that is, free of scutes and scute sulci, forming a ‘distinct recessed lower margin or shelf’ along the rear temporal edge

167 (Gaffney and Kitching 1995: 8). Secondary inner margins to the nasal aperture and cavum tympani are a peculiar feature of Niolamia, Ninjemys and Meiolania and the temporal fossa is partly occluded by a vertical bony arch. The derived state for this character occurs only in australochelyids and meiolaniids.

30. Interpterygoid vacuity: 0 = present; 1 = absent (Gaffney et al. 1991; Gaffney 1996, 1998; Rougier et al. 1995; Gaffney and Kitching 1995; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Sukhanov 2006; Joyce 2007; Gaffney et al. 2006; Sterli et al. 2007). Morphology, distribution and homoplasy: Spoochelys has a large bracket-shaped interpterygoid vacuity. This correlates with presence of postparietal and supratemporal, weak development of the inferior parietal process, deep bone in the primary neurocranium, ventral position and large size of the canalis cavernosus, broad ventral exposure of the basisphenoid, presence of the basisphenoid crista and absence of bony floor to the middle and inner ear. Presence of the interpterygoid vacuity in Spoochelys and Sunflashemys prompts reinterpretation of the ‘intrapterygoid slit’ of meiolaniids. The argument (Gaffney 1996: 119) that ‘posterior extension of the ventral plate of the pterygoid in Dracochelys would come very close to the condition in Niolamia’ infers complex reversals: unzipping of midline sutures, displacement and ‘further separation’ of horizontal alignment between pterygoid and basisphenoid, and posterior expansion of the pterygoid lamellae that form the floor of the opening. The interpterygoid opening in Niolamia is actually situated forward of the otic chamber (pers. obs.), a feature obscured by parallax error in the ventral view shown by Woodward (1901:177: XVI). The rear limit of the interpterygoid vacuity is maintained near the front of the otic chamber throughout meiolaniid evolutionary history. A primitive feature known only in basal groups, the interpterygoid vacuity has not been identified previously in meiolaniids, nor in Chubutemys (Fig. 40; pers. obs., contra Gaffney et al. 2007).

31. Shape of interpterygoid vacuity (New): 0 = rostrocaudal and dorsoventral opening between pterygoid and rostrum basisphenoidale; 1 = dorsoventral opening that is predominantly transverse between pterygoid and rostrum basisphenoidale (Gaffney 1983, 1990; Gaffney et al. 1987; Gaffney and Kitching 1995; Rougier et al. 1995; Sukhanov 2000, 2006; Sterli and Joyce 2007; Sterli et al. 2007).

168 Morphology, distribution and homoplasy: Primitively, the interpterygoid vacuity is predominantly sagittal (Proganochelys, australochelyids, Kayentachelys, Heckerochelys and Chubutemys). In previous analyses, meiolaniids were scored as lacking the interpterygoid vacuity on purported homology of the so-called ‘intrapterygoid slit’ with the foramen posterius canalis caroticus laterale (fpccl), the point of entry into the skull of the palatine artery (Gaffney 1983, 1996; Gaffney et al. 1998; Gaffney et al. 2007). When the interpterygoid vacuity is lost, pterygoids and basisphenoid are aligned horizontally and the anteromedial margins of the pterygoid are sutured to the basisphenoid rostrum, either parasagittally (Araripemys, ‘pleurosternids’, Sinemys), or on the midline (other pleurodires and cryptodiromorphs). The bracket-like shape of the opening in Spoochelys that is also present in Crossochelys (Simpson 1938: 232: 7) is ancestral to the condition in Tertiary meiolaniids in which pterygoid lamellae create a transverse cantilever or shelf below and separated from the basisphenoid. In meiolaniids, a sutured or fused connection may form between basisphenoid crista and pterygoids, but this is hidden in ventral view and the medial margins of the pterygoid lamina remain free and unsutured. Spoochelys illustrates basicranial states for primitive meiolaniids, and is united with Triassic and Jurassic forms on presence of the interpterygoid vacuity. The wide crescentic shape of the opening is an unambiguous synapomorphy uniting Spoochelys and the meiolaniids. The interpterygoid vacuity was lost independently in pleurodiromorphs and cryptodiromorphs.

32. Basisphenoid-basioccipital medial process: 0 = unpaired; 1 = paired (Gaffney 1979; Rougier et al. 1995; Sukhanov 2000; Sterli et al. 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: This character refers to the shape of the basisphenoid projection below the basioccipital. The basisphenoid tubercle is single in Proganochelys, although paired in australochelyids (Sterli et al. 2007). The bifurcation is prominent in Spoochelys, Sunflashemys and Notoemys but absent in other basal taxa and most turtles. The divided basisphenoid in Glyptops () and Dracochelys (Sinochelyidae) are reversals according to this analysis.

169 33. Condylaris mandibularis position: 0 = posterior to basisphenoid-basioccipital suture; 1 = near or in line with basisphenoid-basioccipital suture; 2 = anterior to basisphenoid-basioccipital suture (Gaffney et al. 2006). Morphology, distribution and homoplasy: This character, first used by Gaffney et al. (2006) to acknowledge variations in position of the mandibular condyle relative to the primary basicranium in pleurodires, is here applied to a range of stem taxa and crown cryptodires. As discussed by Gaffney et al. (2006) the character is a continuum, however meiolanoids resemble stem groups and pleurodires rather than cryptodires in the anterior position of the mandibular condyle.

34. Processus trochlearis pterygoidei: 0 = absent; 1 = present (Gaffney 1975; Gaffney and Meylan 1988; Gaffney et al. 1991; Rougier et al. 1995; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Lapparent de Broin 2000; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: Proganochelys and australochelyids show no evidence of a ‘pulley’ mechanism for redirection of the jaw adductor muscle. Pleurodires and cryptodires are separated by fundamental differences in the trochlear systems that evolved to lengthen and strengthen this musculature. The two current hypotheses concerning development of this structure are contradictory. Some analyses have shown that the processus trochlearis pterygoidei developed in Panpleurodira following loss of the processus trochlearis oticum (Joyce 2007; Sterli and Joyce 2007; Sterli et al. 2007; Sterli 2008). This is strongly disputed by Gaffney et al. (2006) and Gaffney et al. (2007). The pleurodiran structure consists of an upwardly-rolled, cylindrical edge producing a posteriorly-directed tubular cavity on the dorsal surface of the transverse pterygoid process. This pterygoid trochlear was probably acquired below Pleurodira (Lapparent de Broin 2000) and the processus was probably parallel to the skull axis in primitive groups (Meylan 1996). The pterygoid margin in Proganochelys and Palaeochersis is rolled ventrally; cranial data for Proterochersis is unavailable; and as the front section of the skull is missing, the condition in Notoemys is unclear. The pterygoid margin in Spoochelys is thickened but the condition is ambiguous. However in Meiolania the condition is unequivocal and surprising – in AMF43813 and MM13825a, specimens preserving the palate section, the edge of the transverse pterygoid

170 process is thickened and curved upwards, forming on the dorsal surface a trench- shaped cavity opening posteriorly, parallel to the skull axis (pers. obs). Although relatively small, this structure is a processus trochlearis pterygoidei and the chelid morphology for example would be obtained merely by posteroventral development of the lateral rim of the dorsal concavity. This key feature, a primary pleurodiran synapomorphy, has not been recognized previously in meiolaniids. The pterygoid trochlear in Meiolania is unlikely to be an independent acquisition and additional fossil evidence for pleurodiran stem taxa might see presence of the processus trochlearis pterygoidei uniting a more inclusive clade. In the absence of preserved palates for Proterochersis and platychelyids, the feature unites Meiolania and crown group pleurodires.

35. Processus trochlearis oticum: 0 = absent; 1 = present (Gaffney 1975; Gaffney et al. 1991; Rougier et al. 1995; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: In cryptodires, the otic chamber rather than the pterygoid functions to redirect the jaw adductor muscle. The cryptodiran processus trochlearis oticum is an anterior thickening or projection from the prootic and/or quadrate into the lower temporal fossa (Gaffney 1975), usually marked by roughened bone surface. Previous analyses scored the cryptodiran trochlear process as present in meiolaniids. However, the cavum tympani is weirdly small in Niolamia, and in Meiolania the cavum tympani is weirdly inflated, a huge balloon- like chamber that expands the otic chamber from behind. Remarkably smooth and thin, the front of the otic chamber in Meiolania is actually the anteromedial wall of the cavum tympani. The otic trochlear in cryptodires, formed by thickening and protrusion of the otic chamber, is unrelated to structure of the cavum tympani. Joyce (2007) argues that Meiolania and Mongolochelys exhibit an incipient cryptodiran trochlear because the jaw muscle is reoriented by the otic chamber which blocks the direct line between origin and insertion of the adductor musculature on the supraoccipital crest. This may be valid for Mongolochelys but in Spoochelys, Sunflashemys and Niolamia, the front of the otic chamber is narrow and perpendicular as in primitive turtles and pleurodires. Spoochelys demonstrates that the supraoccipital crest is undeveloped in basal meiolanoids. Moreover, in

171 Meiolania, the mandibular condyles are positioned further forward relative to the neurocranium than in Proganochelys, locating the coronoid process anteriorly below the orbit, allowing the adductor muscle direct posterodorsal passage to the rear braincase wall. In Meiolania, the only structures impinging on the jaw musculature are medial to the main body of muscle - the processus trochlearis pterygoidei and the epipterygoid. The trochlear process is absent in Chubutemys (pers. obs.; contra Gaffney et al. 2007). The processus trochlearis oticum is absent in basal turtles, Meiolania, meiolanoids and pleurodires.

36. Vertical parasagittal plate on transverse pterygoid process: 0 = absent; 1 = present (Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Phylogenetic significance of structure of the transverse pterygoid process is controversial. The analysis of Gaffney et al. (2007) implies that the vertical parasagittal plate is a pre-cryptodiran feature. Sterli and Joyce (2007) and Sterli et al. (2007) maintain that the upwardly-rolled edge (processus trochlearis pterygoidei) that is synapomorphic for Pleurodira developed from this vertical pterygoid flange, a scenario also suggested by the present analysis. The vertical parasagittal plate is apparently absent in Kayentachelys but a small vertical structure is present in Heckerochelys, and the plate is well developed in Asian eucryptodires such as Dracochelys. There may be a small lateral thickening in Spoochelys but when skull and lower jaw of Niolamia (L1418) are re- articulated, there is simply no space for such a structure. The feature is absent in Meiolania, Mongolochelys and Kallokibotion. According to this analysis, the vertical plate on the transverse pterygoid process unites a clade consisting of Heckerochelys and crown cryptodires (Paracryptodira and Eucryptodira).

37. Pterygoid, posteroventral flange along lateral edge, medial to transverse pterygoid process (Gaffney et al. 2006).

38. Epipterygoid: 0 = present; 1 = absent (Gaffney and Meylan 1988; Gaffney et al. 1991; Shaffer et al. 1999; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007; Sterli 2008).

172 Morphology, distribution and homoplasy: The turtle epipterygoid is highly variable, at times reduced to a flake of bone, or fused with surrounding elements (Gaffney 1979). The epipterygoid is present in basal taxa and variously in cryptodires, and its loss is considered diagnostic for Pleurodira. While Gaffney (1990) was uncertain as to placement and contacts of the epipterygoid in Proganochelys, in this analysis, the ‘pleurosphenoid’ of Proganochelys is identified as the epipterygoid, on close topological similarity to that element in Spoochelys (see Chapter Two; and below). Epipterygoid morphology in Spoochelys strongly suggests that the epipterygoid was lost along the panpleurodiran stem simply by fusion of the ventral suture with the pterygoid. Possession of the epipterygoid is one of several features in Spoochelys, Sunflashemys and meiolaniids excluding them from Pleurodira.

39. Epipterygoid structure (New): 0 = with dorsolateral flange into subtemporal fossa, foramen nervi trigemini unformed; 1 = with dorsolateral flange into subtemporal fossa, foramen nervi trigemini formed; 2 = without dorsolateral flange, foramen nervi trigemini closed (Gaffney 1979, 1985, 1990; Sterli and Joyce 2007; Sterli et al. 2007). Morphology, distribution and homoplasy: The epipterygoid is large and the trigeminal foramen is unformed in Proganochelys and Kayentachelys (Sterli and Joyce 2007). The epipterygoid is undescribed or unknown in many basal taxa (including Palaeochersis; Sterli et al. 2007) but is comparatively reduced in Mongolochelys, Kallokibotion, paracryptodires and Solnhofia (Gaffney 1975). In Spoochelys and Meiolania, the epipterygoid is hypertrophied, elongate and triradiate in section dorsally, contacting the parietal, and extends ventrally below the rostrum basisphenoidale. The trigeminal foramen is closed and the epipterygoid sends into the subtemporal fossa a lateral flange similar in some respects to that of Kayentachelys (Sterli and Joyce 2007). It is possible that in basal groups, this dorsolateral extension of the epipterygoid functioned to redirect the jaw adduction musculature. If so, the two primary adduction systems of turtles may have developed independently from a primitive condition in which a ‘processus trochlearis epipterygoidei’ reoriented the adductor muscle laterally around the front wall of the braincase. The pleurodiran and cryptodiran trochlears direct the muscle vertically. State ‘1’ of this character unites Spoochelys and Meiolania.

173 40. Foramen nervi trigemini formed by prootic and epipterygoid, which forms posterior margin of foramen interorbitale (New): 0 = no; 1 = yes (Gaffney 1979, 1985, 1990; Sterli and Joyce 2007; Sterli et al. 2007). Morphology, distribution and homoplasy: In Spoochelys, Sunflashemys and Meiolania, the trigeminal foramen is formed entirely by the prootic and epipterygoid, and the epipterygoid forms most of the posterior margin of the foramen interorbitale. No other turtles possess an epipterygoid of this size and configuration. The topmost part of the anterior braincase wall in Niolamia and Chubutemys is not visible, however the epipterygoid is triradiate in section dorsally and agrees well with Spoochelys.

41. Processus inferior parietalis: 0 = undeveloped; 1 = slightly developed; 2 = developed (Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2008). Morphology, distribution and homoplasy: This character concerns development of the cavum epiptericum, the anterior extension of the braincase, formed by the parietal descending process. In Proganochelys, the descending process is absent, ventral contacts of the parietal are limited to prootic and supraoccipital and the epipterygoid (‘pleurosphenoid’) extends well forward of the braincase. A similar condition pertains in Kayentachelys (Sterli and Joyce 2007). In Spoochelys and meiolaniids, although the parietal is very short, it contacts the epipterygoid and prootic above the trigeminal foramen. The processus inferior parietalis is developed in Kallokibotion: the parietal contacts prootic and epipterygoid, reaching further forward into the subtemporal fossa than the epipterygoid. While data is unavailable for most primitive turtles, Spoochelys and Meiolania appear to exhibit a unique intermediate condition and are united by the weakly developed state of the processus inferior parietalis. The descending process of the parietal is formed in all other turtles.

42. Acute quadrate margin: 0 = absent; 1 = present (Gaffney 1990; Rougier et al. 1995; Gaffney et al. 2006; Joyce 2007; Sterli 2008).

174 43. Cavum tympani: 0 = absent; 1 = small or moderately developed; 2 = deeply excavated (Gaffney et al. 1991; Gaffney and Kitching 1995; Rougier et al. 1995; Shaffer et al. 1997; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007). Morphology, distribution and homoplasy: Primitively, there is no lateral wall to the middle ear. The cavum tympani is ‘relatively shallow’ in Heckerochelys (Sukhanov 2006) but constricted to a funnel shape in Kayentachelys and other turtles. The cavum tympani is formed in Notoemys, the Lightning Ridge taxa and Tertiary meiolaniids. There are no reversals and the primitive condition in australochelyids may signal independent acquisition within the crown groups.

44. Precolumellar fossa: 0 = absent; 1 = present (Gaffney 1979; Meylan 1996; Shaffer et al. 1997; Gaffney et al. 2006; Joyce 2007). Morphology, distribution and homoplasy: A pleurodiran feature, the precolumellar fossa is a concavity formed in the anterolateral surface of the cavum tympani, below and lateral to the incisura, strongly developed in pelomedusoids (Shaffer et al. 1997). The precolumellar fossa in Spoochelys is similar to that of the chelid Elseya.

45. Eustachian tube within incisura columellae auris: 0 = absent; 1 = present (Shaffer et al. 1997; Gaffney 1990; Hirayama et al. 2000; Joyce 2004; Gaffney et al. 2007). Morphology, distribution and homoplasy: The derived condition in which stapes and eustachian tube are contained in a large opening is seen in Spoochelys, Sunflashemys, Meiolania and pleurodires and also in basal taxa such as Mongolochelys and Kallokibotion. The derived condition appears to have developed independently in pleurodiromorphs and cryptodiromorphs.

46. Antrum postoticum: 0 = unformed; 1 = formed (Gaffney et al. 1991; Gaffney and Kitching 1995; Rougier et al. 1995; Meylan 1996; Shaffer et al. 1997; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007; Sterli et al. 2007). Morphology, distribution and homoplasy: The posterodorsal chamber of the cavum tympani, the antrum postoticum, is undeveloped in Proganochelys and australochelyids, and the antrum is conspicuously absent in Niolamia and other

175 Tertiary meiolaniids. A large antrum postoticum is considered primitive for pleurodires and the antrum is moderately developed in Notoemys (Meylan 1996), apparently formed partly by the squamosal (Fernandez and de la Fuente 1994: 85: 2D) as in Spoochelys. Turtles other than Proganochelys, australochelyids and meiolaniids are united on presence of the antrum postoticum. The antrum postoticum is formed by quadrate alone in more derived pleurodires and primitive cryptodires.

47. Cranioquadrate space or canalis cavernosus (New): 0 = cranioquadrate space opens ventral to fenestra ovalis; 1 = canalis cavernosus large, opens ventral to fenestra ovalis; 2 = canalis cavernosus reduced, opens dorsal to fenestra ovalis (Gaffney 1990; Gaffney and Kitching 1995; Sukhanov 2000, 2006; Sterli 2008). Morphology, distribution and homoplasy: This character tracks progressions in bony enclosure of the cranioquadrate space, the cavity surrounding the primary neurocranium in Proganochelys, and its dorsal relocation as a closed canal in derived turtles. The passage in Proganochelys is continuous with the space ventral to the inner ear, extending below the stapes and fenestra ovalis. The canalis cavernosus is developed in Australochelys (Gaffney and Kitching 1995) and Palaeochersis (Sterli et al. 2007), still in the primitive ventral position. These features are undescribed in other basal taxa, however in the meiolaniid cf. Warkalania from Riversleigh and Meiolania (Gaffney 1996: 70-73: 58-62), the canalis cavernosus is uniquely large and unconstricted, opening well below the level of the fenestra ovalis. Similar morphology is a pronounced feature of Spoochelys and Sunflashemys. Data is missing for Proterochersis and Notoemys, but the sulcus cavernosus appears to lie ventral to the cavum labyrinthicum in Araripemys (Meylan 1996: 27: B). The small, fully enclosed canalis cavernosus, opening dorsal to the incisura columellae auris, stapes and fenestra ovalis unites turtles exclusive of Proganochelys, australochelyids, meiolaniids, Spoochelys and Sunflashemys.

48. Quadrate, medial process contacting braincase elements and underlying cranioquadrate space: 0 = absent; 1 = present (Gaffney and Meylan 1988; Gaffney et al. 1991; Fuente and Iturralde-Vinent 2001; Gaffney et al. 2006).

176 49. Ventral exposure of prootic: 0 = not concealed by pterygoid; 1 = partly concealed by pterygoid; 2 = fully concealed by pterygoid (Gaffney 1975, 1979; Gaffney and Meylan 1988; Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Sterli and Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Pleurodires and cryptodires differ substantially in the manner by which the primary basipterygoid articulation was progressively reinforced. The prootic is strongly exposed in ventral view in Proganochelys, australochelyids, Kayentachelys, Condorchelys, the Lightning Ridge taxa and Notoemys. This is also the case in Chubutemys (Fig. 40), in which the pterygoid is very widely separated from the basioccipital, a feature not obvious in photographs and figures of the type skull (pers. obs.; contra Gaffney et al. 2007). Pterygoid extension below the prootic is weakly developed in Heckerochelys and Mongolochelys, expanding further across the inner and middle ear in Kallokibotion, and in most cryptodires, the pterygoid completely conceals the prootic. As demonstrated by the Lightning Ridge taxa, the pterygoid is very widely separated from the basioccipital in meiolaniids primitively, and caudomedial extension of the pterygoid can be traced as an independent development through Crossochelys, the meiolaniid cf. Warkalania from Riverseigh and Meiolania. According to this analysis, prootic exposure in platychelyids and pleurodires developed as a reversal from state ‘2’ of this character – one of many suggested transitions that is probably due to absence of data for pleurodiran precursors. Further development of the ventrally exposed prootic and/or the quadrate secures the primary contact between basisphenoid and pterygoid in pleurodires.

50. Basisphenoid ventral outline: 0 = elongate, not sutured to pterygoids; 1 = more triangular; 2 = more pentagonal (Gaffney et al. 2006).

51. Basisphenoid, basioccipital cross section: 0 = thick; 1 = thinner (Gaffney 1990; Gaffney and Kitching 1995; Gaffney et al. 2006).

52. Ventral exposure of basisphenoid (New): 0 = narrow, less than one third of skull width; 1 = broad, one third or more of skull width (Gaffney 1979, 1990; Sukhanov 2000; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007).

177 Morphology, distribution and homoplasy: This character recognises important differences in basisphenoid structure among basal groups. The primitive condition is shown by Proganochelys, a narrow basisphenoid with limited ventral exposure. In marked contrast, strong ventral exposure of a massive basisphenoid unites Spoochelys, Sunflashemys, primitive pleurodires such as Notoemys, Araripemys, Brasilemys and Cretaceous chelids. The basisphenoid is relatively broad in Kayentachelys and primitive Asian eucryptodires, although not to the degree seen in the southern hemisphere groups. Data is missing for Proterochersis and Indochelys.

53. Basipterygoid process and basipterygoid articulation: 0 = basipterygoid process present with a moveable basipterygoid articulation; 1 = basipterygoid process present with a sutured basipterygoid articulation; 2 = basipterygoid process absent with a sutured basipterygoid articulation (Joyce 2007; Gaffney et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: The kinetic basipterygoid articulation is only known for Proganochely. In all other turtles, the primary articulation between basisphenoid and pterygoid is sutured. However certain basal taxa retain the primitive basipterygoid process, a lateral flange from the basisphenoid that projects into the medial face of the pterygoid. It is tempting to speculate that the unsutured basipterygoid fissure in meiolaniids is a unique derivation of the primitive kinetic basipterygoid articulation. The basipterygoid process is distinctly present in Chubutemys (pers. obs.) and Sunflashemys, less distinct in Spoochelys (perhaps due to poor preservation). In chelid pleurodires, a large basipterygoid process extends along most of the rear section of the basisphenoid (Gaffney 1979: 135: 44A; and pers. obs.), a prominent feature that is not apparent in ventral view of the articulated basicranium in this group. There are no reversals within the focus taxa.

54. Pterygoid sutured to posterolateral section of basisphenoid and anterolateral section of basioccipital (New): 0 = no; 1 = yes (Gaffney 1975, 1979; Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Gaffney et al. 2006; Joyce 2007). Morphology, distribution and homoplasy: In primitive cryptodires, subsequent to sutural connection of the pterygoid to the posterolateral edge of the basisphenoid,

178 sutures between pterygoid and basioccipital initially developed at the anterolateral edge of the basioccipital. At least this degree of pterygoid-basioccipital connection is seen in Kallokibotion and primitive cryptodires, including pleurosternids. In basal turtles, including the Lightning Ridge taxa and primitive pleurodires, pterygoid and basioccipital are widely separated by the basisphenoid. Previous phylogenetic work has not acknowledged the unique meiolaniid condition in which even though the pterygoid is partly fused to the ventral surfaces of basisphenoid and basioccipital, the posteromedial face of the pterygoid is not suturally connected to either element. A large fissure-like cavity that was presumably filled with cartilage in life (Gaffney 1983) separates the bones along those exact points of contact where sutures first develop in cryptodires. Outside this area of overlap, the pterygoid expansion in meiolaniids progressively (but variably) fuses to the ventral surfaces of adjoining elements, as shown by transitions through Sunflashemys, Crossochelys, the meiolaniid cf. Warkalania from Riversleigh and Meiolania. The fissure between the caudomedial face of the pterygoid and the basisphenoid and basioccipital remains open throughout meiolaniid evolutionary history. The pterygoid floor to the middle and inner ear in meiolaniids is not homologous with that of cryptodires. The primitive meiolaniid condition demonstrated by the Lightning Ridge taxa resembles Triassic and Jurassic turtles and pleurodires such as Notoemys. Acquisition of a sutured contact between the pterygoid and the posterolateral section of the basisphenoid and anteroventrolateral edge of the basioccipital unites Kallokibotion and crown group cryptodires. There is no evidence of homoplasy in the groups under consideration.

55. Inner ear or cavum labyrinthicum (New): 0 = floored by prootic/opisthotic or basisphenoid/opisthotic; 1 = open ventrally, margins formed by prootic, opisthotic, basisphenoid and basioccipital; 2 = floored by prootic and/or quadrate; 3 = with pterygoid margin or floored by pterygoid (Hirayama et al. 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Primitively, the cavum labyrinthicum is closed ventrally by sutural connection of prootic and opisthotic (Proganochelys and australochelyids). It is closed by basisphenoid and opisthotic in Kayentachelys (Sterli and Joyce 2007). Although the prootic floors the cavum labyrinthicum in the meiolaniid cf. Warkalania from Riversleigh, the primitive state for meiolaniids is

179 shown in Spoochelys and Sunflashemys, in which the inner ear is widely open, with the lower medial margin formed by basisphenoid and basioccipital, the same condition as in Chubutemys (Fig. 40) and Notoemys. In Heckerochelys and Mongolochelys the inner ear is open but the pterygoid contributes to the anteroventral border. The inner ear is open or variably floored by basisphenoid, prootic and/or quadrate in pleurodires and by the pterygoid in cryptodires. In this analysis, state ‘1’ of this character is given as a reversal from state ‘3’ in the platychelyids and Pleurodira, another character change that is likely due to missing data.

56. Extended basisphenoid margin of open cavum labyrinthicum (New): 0 = absent; 1 = present; 2 = present, with margin formed by posterolateral shelves of basisphenoid dorsal to ventral surface of basicranium (Gaffney 1979, 1990, 1996; Gaffney et al. 2006). Morphology, distribution and homoplasy: The cavum labyrinthicum is closed primitively. Spoochelys and Sunflashemys exhibit a condition in which shelf-like lobes of the basisphenoid form the medial margin of the inner ear, dorsal to the ventral surface of the basicranium. The posterolateral ‘free’ edges of the basisphenoid are uniquely long and highly distinctive. Chubutemys and Notoemys are similar, but do not appear to have the cantilevered shelf-like structures seen in the Lightning Ridge taxa.

57. Hyomandibular branch VII of facial nerve: 0 = traverses cranioquadrate space (canalis cavernosus); 1 = separated by bone from cranioquadrate space (canalis cavernosus) (Gaffney and Meylan 1988; Gaffney et al. 1991; Rougier et al. 1995; Gaffney 1996, 1998; Shaffer et al. 1997; Sukhanov 2006; Gaffney et al. 2006; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Variation in facial nerve structure is a critical test of the ‘casichelyidian’ dichotomy (Gaffney 1975, 1979; Rougier et al. 1995; Gaffney et al. 2007; Joyce 2007; Sterli 2008). In Proganochelys, two distal branches of the facial nerve open from the prootic into the posterior section of the cranioquadrate space (Gaffney 1990; Gaffney et al. 2006). In pleurodires the hyomandibular branch (VII) of the facial nerve ‘is usually subdivided within the canalis cavernosus in its own canal’ (Gaffney et al. 2006: 28). In cryptodires, the

180 hyomandibular branch is carried in the foramen pro ramo nervi vidiani between the canalis caroticus internus and the canalis cavernosus. Facial nerve structure in Meiolania is fundamentally different from that of cryptodires (contra Gaffney 1983), as shown unequivocally in Sunflashemys and the meiolaniid cf. Warkalania from Riversleigh. The canalis nervi facialis is enclosed in bone and separated from the canalis cavernosus, opening into the cavum acustico-jugulare as in Elseya and Emydura (Gaffney 1975). This resembles the condition in Notoemys, in which the facial nerve exits from the prootic wall, between canalis cavernosus and cavum labyrinthicum (Marcelo de la Fuente pers. commun.). Data is missing for Proterochersis. The condition in Palaeochersis is unclear: the facial nerve is separated from the cranioquadrate space according to Rougier et al. (1995), contradicted by Sterli (2008), however neither paper provides a description. Bony separation of the hyomandibular branch of the facial nerve (VII) from the canalis cavernosus unites the Lightning Ridge taxa, meiolaniids, Notoemys and crown group pleurodires.

58. Foramen posterius canalis caroticus laterale in suture between medial margins of pterygoid and anterior section of rostrum basisphenoidale (New): 0 = no; 1 = yes (Gaffney 1996; Sukhanov 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: In Mongolochelys, Kallokibotion and primitive cryptodires, the foramen posterius canalis caroticus laterale (fpccl) are small paired openings, visible in ventral view, entering the midline suture between the medial margin of the pterygoids and the anterior section of the rostrum basisphenoidale. There is no ancillary or extraneous opening and the suture is either acuminate (Dracochelys) or transverse (Mongolochelys, Kallokibotion, Ordosemys and Hangaiemys). This derived condition is present in Mongolochelys, Kallokibotion and primitive Asian eucryptodires and is otherwise absent in turtles. The condition is fundamentally different in Spoochelys, meiolaniids and Chubutemys in which the anteromedial edges of the pterygoids are not sutured across the midline to the basisphenoid. Data is missing for Proterochersis and platychelyids.

59. Foramen basisphenoidale: 0 = formed by basisphenoid, equals fpcci; 1 = formed by basisphenoid and pterygoid, equals fpcci; 2 = formed by basisphenoid

181 and pterygoid, more posterior fpcci present; 3 = absent due to prootic forming fpcci; 4 = absent due to solid pterygoid covering (Gaffney et al. 2007).

60. Foramen posterius canalis carotici interni: 0 = foramen caroticum basisphenoidale; 1 = formed in part by basisphenoid; 2 = formed entirely by pterygoid; 3 = formed by prootic (Gaffney et al. 2006).

61. Foramen posterius canalis carotici interni: 0 = not formed by basisphenoid and pterygoid; 1 = formed by basisphenoid and pterygoid, located midway along basisphenoid-pterygoid suture (Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1996, 1998; Shaffer et al. 1997; Hirayama et al. 2000; Parham and Hutchison 2003; Joyce 2007; Gaffney et al. 2007). Morphology, distribution and homoplasy: Variations in position of the foramen posterius canalis carotici interni have been repeatedly used to test turtle relationships. In advanced turtles, the foramen is either in the prootic and/or quadrate (pleurodires) or pterygoid (cryptodires). The foramen is located halfway along the basisphenoid-pterygoid suture in Glyptops, pleurosternids and baenids. The derived state of this character is synapomorphic for Paracryptodira.

62. Recessus scalae tympani: 0 = unformed; 1 = formed, unenclosed ventrally; 2 = formed, closed ventrally (Rougier et al. 1995; Lapparent de Broin 2000; Joyce 2007; Sterli 2007). Morphology, distribution and homoplasy: The recessus scalae tympani is unformed in Proganochelys and australochelyids. The recessus is present but unfloored in Kayentachelys, Heckerochelys, the Lightning Ridge taxa, Chubutemys and primitive pleurodires (Notoemys and Araripemys). In other turtles, the recessus is closed ventrally by the exoccipital and/or pterygoid, or by the basioccipital. Development of the floor to the recessus scalae tympani occurred independently in Pleurodira and Cryptodira, and in Tertiary meiolaniids.

63. Foramen jugulare posterius: 0 = absent; 1 = present (Rougier et al. 1995; Joyce 2007). Morphology, distribution and homoplasy: The foramen jugulare posterius is absent in basal turtles. Data is missing for Proterochersis but the foramen is undeveloped

182 in the Lightning Ridge taxa, Notoemys, Niolamia and the meiolaniid cf Warkalania from Riversleigh. Among meiolaniids, the foramen occurs only in Meiolania, formed between pterygoid and exoccipital and related to posteromedial extension of the pterygoid. This is independently acquired from the foramen jugulare posterius of pleurodires and cryptodires.

64. Large splenial extending to lower jaw rim (New): 0 = present; 1 = splenial reduced or absent (Gaffney 1979, 1990; Burbridge et al. 1988; Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Parham and Hutchison 2003; Gaffney et al. 2006; Joyce 2007; Sterli and Joyce 2007; Sterli 2008).

65. Contact of splenial and dentary in meckelian sulcus anterior to foramen intermandibularis medius (New): 0 = no; 1 = yes (Gaffney 1979; Gaffney 1983). Morphology, distribution and homoplasy: In Proganochelys and primitive taxa, the foramen intermandibularis medius is located anterior to the splenial-dentary contact that covers the rear section of the meckelian sulcus (Gaffney 1979, 1982, 1983, 1990). Spoochelys, Opalania and Meiolania exhibit a unique additional splenial- dentary contact in the meckelian sulcus, anterior to the foramen intermandibularis medius. In this analysis, this derivation has a CI of 1.00 and unites Spoochelys and the meiolaniids.

Carapace and plastron 66. High vaulted domed carapace (New): 0 = absent; 1 = present (Gaffney et al. 1987; Gaffney 1990; Lapparent de Broin 2000; Sukhanov 2000; Lapparent de Broin 2000). Morphology, distribution and homoplasy: The carapace of Proganochelys and Kayentachelys is moderately domed (Gaffney et al. 1987; Gaffney 1990). While the condition is uncertain for australochelyids, the strongly vaulted carapace that is seen in Proterochersis is also a pronounced feature of the three Lightning Ridge taxa and Tertiary meiolaniids. The carapace is low in platychelyids (Lapparent de Broin 2000) and further flattened in pelomedusoids and primitive chelids, as in Heckerochelys, Mongolochelys and eucryptodires. Data is missing for Otwayemys and the structure is unclear in Chelycarapookus and Indochelys. Flattening of the carapace occurs independently in crown groups.

183 67. Curvature of anterior carapace margin (New): 0 = transverse or indented; 1 = rounded, midline area extends forward (Fraas 1913; Pritchard 1984; Gaffney et al. 1987; Gaffney 1990; Rougier et al. 1995; Lapparent de Broin 2000; Sukhanov 2000; Joyce 2007). Morphology, distribution and homoplasy: The indented or transverse carapace front (nuchal embayment) of Proganochelys, Kayentachelys and Mongolochelys is a clear contrast to the extended and forwardly-curved carapace of Proterochersis, Palaeochersis, Indochelys, Meiolania, primitive pleurodires and Spoochelys. This feature which may be an early indicator of the trend to lateral neck retraction also appears to be present in Chelycarapookus and is strongly developed in turtle material from Victoria (NMVP199057 from Kilcunda Strzelecki Group and NMVP208303 (MSC220) from Inverloch). The rounded carapace front in Glyptops, Pleurosternon (Hirayama et al. 2000), (Hirayama 1998) and certain Asian eucryptodires is homoplasic, according to this analysis.

68. Prominent or bulbous cervical scute (New): 0 = absent; 1 = present (Shaffer et al. 1997; de la Fuente and Iturralde-Vinent 2001; Rueda and Gaffney 2005; Joyce 2007). Morphology, distribution and homoplasy: A broad but recessed cervical scute is the presumed primitive state. The cervical scute in Proterochersis is wide and domed anteriorly, as in Spoochelys, Meiolania and Pseudemydura umbrina Siebenrock 1901. A heavy bean-shaped cervical scute is also present in NMVP208303 (MSC220) from Victoria. The cervical scute is similar but less prominent in Notoemys and Platychelys. Stem cryptodires and Asian eucryptodires do not exhibit the derived state of this character. Palaeochersis is scored ‘1’ for this character, on presence of a small midline anterior projection (Sterli et al. 2007: Pl. 7A).

69. Anal notch separating rear marginals: 0 = present; 1 = absent (Gaffney 1990; Rougier et al. 1995; Sukhanov 2000; Joyce 2007).

70. Lateral edge of forwardly curved anal notch forms posterior limit of carapace (New): 0 = no; 1 = yes (Lapparent de Broin et al. 2004; Sterli et al. 2007).

184 Morphology, distribution and homoplasy: The derived state of this character applies only to Palaoechersis and Proterochersis, in which the peripheral bones that adjoin the pygal notch form the posterior limit of the carapace. In Proganochelys, the pygal notch is not curved and the peripherals that form the posterior limit of the carapace are separated from the anal notch. This is an unambiguous synapomorphy for Palaeochersis and Proterochersis.

71. Nuchal articulation with eighth cervical vertebra: 0 = facet elongate; 1 = circular nubbin (Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: The neural spine of the eighth cervical vertebra is fused or sutured to the nuchal in Proganochelys (Gaffney 1990), but the cervical-nuchal connection is absent in Palaeochersis (Sterli et al. 2007). A ‘blunt facet’ (Sukhanov 2006; Joyce 2007) for connection with the eighth cervical vertebra occurs in Kayentachelys and other basal taxa. In Meiolania, Chelycarapookus and NMVP208303 from Inverloch, Victoria, the nuchal articulation is a low circular nubbin, and although there is no direct evidence from carapace material, a similar attachment is inferred for Spoochelys and Otwayemys (Gaffney et al. 1998) due to the tall neural spine of the eighth cervical. Data is missing for other basal forms. In Araripemys there is no cervico-nuchal connection but the first thoracic vertebra is sutured to the nuchal along a well-developed ridge (Meylan 1996). Loss of cervico-nuchal articulation may occur independently in crown groups and the attachment is regained as a homoplasy in chelonioids and carettochelyids. The circular articulation uniting Chelycarapookus, Spoochelys, meiolaniids and at least one of the Inverloch turtles may be another signal that neck flexion was predominantly lateral rather than vertical. The circular nuchal nubbin is an unequivocal synapomorphy (CI of 1.00) supporting monophyly of a clade consisting of Indochelys, Chubutemys and the Australian taxa.

72. Vertebral scutes: 0 = broad; 1 = very broad due to narrowing and elongation of the pleural scutes; 2 = narrow (Hirayama et al. 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Presence of broad vertebral scutes is primitive. Due to the narrow pleurals, vertebrals are very broad in Proterochersis, Indochelys, Condorchelys, Chelycarapookus, Otwayemys and apparently in NMVP199057 from Victoria. Narrow vertebrals occur in Pleurodira, baenids and

185 eucryptodires (Xinjiangchelys). Unfortunately, data is missing for Palaeochersis. Broad vertebrals in Chubutemys, the Lightning Ridge taxa, NMVP199057 and Tertiary meiolaniids are a reversal of the very broad condition.

73. Distal ends of costal ribs fitted between contiguous bridge peripherals (New): 0 = absent; 1 = present (Fernandez and de la Fuente 1994; Rueda and Gaffney 2005). Morphology, distribution and homoplasy: Data is missing for Triassic and Early Jurassic taxa. Given the widespread distribution in stem taxa and basal cryptodires of the condition in which most bridge peripherals bear only one rib end, this is interpreted as the primitive state. The derived condition occurs in better-known Lightning Ridge taxa, platychelyids and primitive pelomedusoids (Brasilemys and Araripemys).

74. Suture between pygal and suprapygal V-shaped posteriorly (New): 0 = absent; 1 = present (Rueda and Gaffney 2005). Morphology, distribution and homoplasy: Once again, a surfeit of missing data. Still, the pointed suprapygal is a distinctive feature of Indochelys, Spoochelys and Notoemys, a further addition to the mosaic of derived features patchily developed in these southern hemisphere forms.

75. Neural count: 0 = more than eight; 1 = eight or less (Gaffney et al. 2006).

76. First vertebral (New): 0 = transverse anterior margin, straight lateral margins; 1 = strongly curved, semicircular anterior margin (Fraas 1913; Bram 1965; Pritchard 1984; Gaffney et al. 1987; Gaffney 1990; Rougier et al. 1995; Datta et al. 2000; Sukhanov 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: The primitive subrectangular first vertebral scute persists in Kayentachelys, Heckerochelys, basal cryptodires and Asian eucryptodires. The ‘inverted bowl’ or mushroom-shaped first vertebral is a distinctive feature of Proterochersis, Indochelys, Notoemys, the two Victorian specimens (NMVP199057 and NMVP208303), Spoochelys and Opalania. In Meiolania, the first vertebral has a rounded front contour but the lateral margins are straight. Unfortunately, data is missing for Sunflashemys. The condition is also uncertain in Palaeochersis, although given the configuration of the anterior section

186 of the carapace, it seems highly likely that the front edge of the first vertebral is strongly curved. The semicircular first vertebral in Xinjiangchelys and Mongolochelys may be homoplasic.

77. Position of vertebral III/IV sulcus, in turtles with five vertebrals: 0 = across neural six; 1 = across neural five (Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: The vertebral III/IV scute sulcus crosses the sixth neural in Kayentachelys, platychelyids, Indochelys, Condorchelys and Chelycarapookus. The vertebral III/IV sulcus lies between neurals five and six of Proterochersis (Fraas 1913: 18: 1). Position of the sulcus is ambiguously figured for Kallokibotion as either on the fifth or sixth neural (Gaffney 1992: 22: 17). The III/IV sulcus traverses neural five in Heckerochelys, Mongolochelys and cryptodires. Data is missing for the Lightning Ridge and Victorian taxa and the Tertiary meiolaniids.

78. Supramarginal scutes: 0 = full set (12 pairs); 1 = less than five; 2 = absent (Gaffney et al. 1991; Rougier et al. 1995; Shaffer et al. 1997; Gaffney 1996, 1998; Brinkman and Wu 1999; Hirayama et al. 2000; Lapparent de Broin 2000; Parham and Hutchinson 2003; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: A full set of supramarginals is present in Proganochelys. Supramarginals appear to be reduced to three pairs in Palaeochersis (Sterli et al. 2007). Indochelys has a conical posterior supramarginal (pers. obs.), as may also be present in Palaeochersis (Sterli et al. 2007). Supramarginals are reduced to three pairs in Proterochersis and two in Platychelys (Lapparent de Broin 2000). The four prominent supramarginals of Spoochelys, restricting the adjoining marginals into tiny triangular shelves on the anterolateral carapace edge, are lanceolate in shape as in Palaeochersis. In meiolaniids, ‘pleating’ of the carapace border may involve supramarginal scutes that impinge on intervening marginals; anterior carapace scutes are also overfolded in Opalania. The only independent acquisition of supramarginals occurs in the baenid Boremys (Paracryptodira; Brinkman and Nicholls 1991). A decreased number of supramarginals unites Palaeochersis, Proterochersis, Indochelys, Platychelys and Spoochelys.

187 79. Inframarginals: 0 = present; 1 = absent (Shaffer et al. 1997; Hirayama et al. 2000; Joyce 2007; Sterli et al. 2007). Morphology, distribution and homoplasy: Inframarginal scutes cover the bridge region of the plastron in many basal taxa, including Kayentachelys, Mongolochelys and pancryptodires. Data is missing for Proganochelys and Palaeochersis. Absence of inframarginals is an unequivocal synapomorphy for the southern hemisphere clade consisting of Indochelys, Chubutemys, the Australian taxa and meiolaniids.

80. Costo-vertebral tunnel: 0 = wider anteriorly and posteriorly; 1 = wide; 2 = reduced (Gaffney 1990; Gaffney et al. 1987; Fernandez and de la Fuente 1994; Gaffney 1996; Sukhanov 2000; de la Fuente and Iturralde-Vinent 2001; Rueda and Gaffney 2005; Gaffney et al. 2006; Sterli et al. 2007). Morphology, distribution and homoplasy: The costo-vertebral tunnel is wider at the front and rear in Proganochelys, Palaeochersis, Proterochersis, Indochelys, Chelycarapookus and Meiolania, a primitive condition that seems to correlate with wider neurals anteriorly and posteriorly. The costo-vertebral tunnel is reduced in Opalania and Sunflashemys, but data is missing for Spoochelys and Otwayemys.

81. Costals: 0 = nine; 1 = eight (Gaffney et al. 1987; Gaffney 1990; Khosatzky 1997; Hirayama et al. 2000; Sukhanov 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Nine costals is the primitive condition. Costal count is uncertain in Heckerochelys (Sukhanov 2006) and unknown for australochelyids, but costals are apparently reduced to eight in Proterochersis (Fraas 1913). Chelycarapookus appears to have nine costals, but the condition in the Lightning Ridge taxa is unclear and reconstructions of the rear carapace are tentative for Meiolania (Gaffney 1996; pers. obs.).

82. Carapace-plastron connection: 0 = sutured; 1 = ligamentous (Meylan and Gaffney 1989; Gaffney 1996; Shaffer et al. 1997; Brinkman and Wu 1999; Joyce 2007; Gaffney et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: This character is problematic (Gaffney 1996; Joyce 2007). The primitive state of the carapace-plastron attachment is uncertain, intermediate morphology typifies many taxa and moreover the connection is ligamentous during ontogeny. The condition in Palaeochersis is

188 undocumented or unknown, but carapace and plastron are suturally connected in Meiolania. The carapace-plastron link is unossified in Kayentachelys and Heckerochelys. Gaffney (1996) suggests that the sutured condition is a pleurodiran synapomorphy and the attachment is sutured in Proterochersis and Platychelys, ligamentous in Notoemys (de Lapparent de Broin 2000) and ‘loose’ in the oldest South American chelids (Lapparent de Broin and de la Fuente 2000). In Spoochelys and Sunflashemys, although axillary and inguinal pegs of the plastron insert into sockets in the peripherals, the bridge section is fully sutured. This appears similar to the condition in Indochelys, Chelycarapookus and NMVP199057. The sutured connection is also cited as primitive for eucryptodires (Gaffney 1996) but the character is obviously homoplasic.

83. Gular points of plastron: 0 = present; 1 = absent (Lapparent de Broin 2000; Gaffney et al. 2006).

84. Entoplastron, anterior section: 0 = reaches front of plastron dorsally and ventrally; 1 = reaches front of plastron dorsally but not ventrally; 2 = does not reach front of plastron (Gaffney 1996; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Primitively in turtles, the entoplastron extends to the front of the plastron, separating the epiplastra. The entoplastron is restricted from the plastron edge dorsally but not ventrally in Meiolania and on the basis of epiplastral morphology, this is the entoplastral condition presumed for Chelycarapookus and NMVP186048, the isolated entoplastron from Dinosaur Cove. Epiplastral broadening and median contact truncates the entoplastron in platychelyids, Heckerochelys, Mongolochelys, Xingjianchelys, paracryptodires and plesiochelyids.

85. Entoplastron, posterior section: 0 = elongate, reaches level of axillary notch; 1 = shortened (Rougier et al. 1995; Hirayama et al. 2000; Joyce 2007; Sterli 2008). Morphology, distribution and homoplasy: Primitively, the entoplastron is very long and has a dorsal keel. The entoplastron is reduced in Kayentachelys, Meiolania, Chelycarapookus and Mongolochelys. Plastral remains are fragmentary and sparse

189 at Lightning Ridge but a low crest may be present in Sunflashemys. The entoplastron is short and the crest is absent in platychelyids and cryptodires.

86. Epiplastra (New): 0 = epiplastra extend posterior to widest part of entoplastron; 1 = epiplastra very elongated beyond widest part of entoplastron; 2 = epiplastra do not extend posterior to widest section of entoplastron (Gaffney 1996; Hirayama et al. 2000; Sukhanov 2000; Joyce 2007). Morphology, distribution and homoplasy: Previous analyses apart from Joyce (2004) use definitions referring to epiplastral width. This rewording acknowledges the relationship between epiplastra and entoplastron, hence the condition in Proganochelys, Palaeochersis, Proterochersis and Heckerochelys is coded as primitive. Data is missing for the Lightning Ridge taxa, however epiplastra are short and broad in Otwayemys, as in Kayentachelys, platychelyids and basal cryptodires. The supernumerary processes in Mongolochelys have been interpreted (discordantly) as gastralia (Khosatzky 1997), as autapomorphic (Sukhanov 2000), and as epiplastral extensions (Joyce 2006). Indochelys also has ‘post-epiplastral’ bones, much larger than those of Mongolochelys, differing in manner of articulation and contacts and this analysis suggests that these are non-homologous.

87. Axillary buttress (New): 0 = short; 1 = elongated anteriorly and tightly curved (Gaffney 1990, 1996; Gaffney et al. 1998; Rougier et al. 1995; Sukhanov 2000; Lapparent de Broin 2000; Rueda and Gaffney 2005; Sterli et al. 2007). Morphology, distribution and homoplasy: The axillary buttress is short in Proganochelys and most turtles, although thickened and strongly reinforced by dorsal contact with the costals in advanced forms, including pleurodires. Elongation and tight curvature of the axillary buttress in Palaeochersis, Proterochersis, Indochelys and Chelycarapookus is a marked departure from the structure in other basal turtles. Spoochelys appears to resemble Chelycarapookus in this feature, but the buttress in Meiolania is undeveloped and does not extend forward.

88. Mesoplastra: 0 = present; 1 = absent (Gaffney et al. 1991; Gaffney 1996, 1998; Brinkman and Wu 1999; Hirayama et al. 2000; Sukhanov 2000; Joyce 2007; Sterli 2008).

190 89. Mesoplastra, size: 0 = midline contact; 1 = no midline contact (Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: Presence of paired mesoplastra, lying between hyoplastron and hypoplastron and contacting on the midline is the primitive condition (Proganochelys). In Kayentachelys, Heckerochelys, Mongolochelys and paracryptodires (Dinochelys and Glyptops), mesoplastra are separated by a plastral fontanelle, as in Indochelys (contra Datta et al. 2000). Proterochersis uniquely has two sets of mesoplastra meeting on the midline (Fraas 1919), however in platychelyids, paired mesoplastra are separated by a plastral fontanelle in addition to hyoplastron-hypoplastron contact. Mesoplastra appear to be absent in Early Cretaceous Australian taxa and Meiolania. Mesoplastra are apparently lost independently in pleurodires and primitive cryptodires.

90. Xiphiplastron: 0 = undivided at rear; 1 = bifid posteriorly (Lapparent de Broin 2000; de la Fuente and Iturralde-Vinent 2001; Lapparent de Broin and de la Fuente 2000). Morphology, distribution and homoplasy: Whereas the rear lobe of the plastron is rounded primitively, it is bifid in pleurodiran stem taxa and pleurodires. In Spoochelys the rear plastral lobe is weakly subdivided, however data is missing for other Lightning Ridge taxa. NMVP199057 from Kilcunda, Victoria, appears to have a strongly bifurcated xiphiplastron (resembling that of primitive chelids) however the structure as preserved is equivocal and the crescent-shaped margin may represent transverse ischial processes (pers. obs.). Bifurcation of the rear xiphiplastron may be synapomorphic for Pleurodira.

Axial skeleton 91. Fusion of atlantal vertebral elements (New): 0 = no; 1 = yes (Hoffstetter and Gasc 1969; Gaffney 1983, 1990; Joyce 2007). Morphology, distribution and homoplasy: In all turtles, the atlantal centrum is biconcave (Joyce 2007), but in most turtles including Proganochelys, central elements are separate. In pleurodires, trionychids and carettochelyids, atlantal bones are variably fused (Gaffney 1985), forming a functionally biconcave vertebra that is correlated with predatory feeding or lateral ‘strike’ capacity (Hoffstetter and

191 Gasc 1969; Pritchard 1984). Atlantal elements are also fused in Meiolania, in accordance with other structures of cervical vertebrae and skull (e.g. laterally- directed horns) suggesting a predominantly lateral mode of neck movement. The uniquely narrow atlantal intercentrum in Proganochelys and Meiolania suggests that the fused atlantal condition in meiolaniids is derived over Proganochelys but primitive compared to other turtles. Unfortunately, data is missing for many primitive groups, including the Lightning Ridge taxa.

92. Cervical articulations: 0 = unformed; 1 = formed (Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Lapparent de Broin 2000; Sukhanov 2000; Joyce 2007). Morphology, distribution and homoplasy: Turtle cervical articulations are either completely unformed or fully formed. Articulations are formed in Spoochelys, Sunflashemys, Otwayemys, Mongolochelys and primitive Asian eucryptodires. Platychelys and Notoemys have well-developed articulations (Bram 1965; Lapparent de Broin 2000; de la Fuente pers. commun. 2006). It has been suggested that primitive members of both crown groups lacked proper cervical joints (Gaffney 1975, 1985, 1990) but formed articulations may be prerequisite to lateral neck movement in turtles, because cervical joints are formed in all known pleurodiromorphs and pleurodires (although data is missing for Proterochersis). In significant contrast, the primitive amphicoelous condition persists in cryptodiromorphs and early cryptodires. Formed cervical articulations developed independently in paracryptodires and the Asian eucryptodires (Joyce 2007).

93. Fourth cervical articulation: 0 = biconcave; 1 = opisthocoelous or procoelous; 2 = biconvex (Gaffney and Meylan 1989; Gaffney et al. 1991; Gaffney 1996; Shaffer et al. 1997; Gaffney et al. 1998; Gaffney et al. 2007; Brinkman and Wu 1999; Hirayama et al. 2000). Morphology, distribution and homoplasy: Cervicals four, five, seven and eight are located within mobile ‘morphogenetic fields’ (Williams 1950). In this analysis, characters relating to cervical articulations for these vertebrae are interpreted on the basis that: a) biconcave centra are primitive in turtles with formed articulations, and cotyles are more primitive than condyles; b) anterior and posterior central

192 articulations probably develop independently (Brinkman and Wu 1999; Hirayama et al. 2000); c) the central condyle results from addition of the cartilaginous intervertebral ring or disc to the centrum (Williams 1950; Hofftstetter and Gasc 1969), a relatively simple process that simultaneously effects the adjacent articulation (Vaillant 1879; Romer 1950); and d) complex articulation patterns arise following formation of a biconvex centrum, which is more derived than an opisthocoelous or procoelous centrum. The biconvex fourth cervical uniting Spoochelys, Sunflashemys and Meiolania differentiates them from primitive pleurodires in which the fourth cervical is opisthocoelous and the fifth biconvex. Development of a biconvex fifth from a biconvex fourth (or vice versa) requires transfer of only one intervertebral disc between two adjoining centra. Cervical articulations are unformed primitively in cryptodires and the biconvex fourth in basal members is associated with multiple articulation patterns suggesting complex transitional pathways. The ‘centrocryptodiran’ biconvex fourth is not homologous with the biconvex fourth of meiolaniids and the Lightning Ridge taxa.

94. Fifth cervical articulation: 0 = biconcave; 1 = opisthocoelous or procoelous; 2 = biconvex (Gaffney 1975; Gaffney et al. 1988; Gaffney and Meylan 1991; Shaffer et al. 1997; Lapparent de Broin 2000; Gaffney et al. 2007; Joyce 2007). Morphology, distribution and homoplasy: The biconvex fifth cervical vertebra that is synapomorphic for chelids may also be present in Platychelys and Notoemys (Lapparent de Broin 2000; Marcelo de la Fuente pers. commun. 2006). This vertebra is procoelous in Spoochelys, Sunflashemys and Meiolania. Although a biconcave fifth is known in Boremys (Brinkman and Nicholls 1991) and possibly Ordosemys (Brinkman and Peng 1993), Williams (1950: 536) asserts that the fifth cervical is never amphicoelous. Perhaps the isolated cervical identified as a biconcave fifth for Otwayemys NMVP186224 (Gaffney et al. 1998) is better interpreted as a seventh as in the Lightning Ridge turtles. Within the analysed taxa, the biconvex fifth is restricted to platychelyids and chelids.

95. Seventh cervical articulation: 0 = biconcave; 1 = opisthocoelous or procoelous; 2 = biconvex (Lapparent de Broin 2000; Gaffney et al. 1998; Gaffney et al. 2007; Joyce 2007).

193 Morphology, distribution and homoplasy: The biconcave seventh assumed for Platychelys and Notoemys (Lapparent de Broin 2000) is otherwise confined to chelids and the Lightning Ridge taxa. The seventh cervical of Spoochelys conforms very closely with that of chelids in the hypertrophied neural arch pedicel, rear position of postzygapophyses, ventrally pinched centrum and triangular posterior central facet. Derivation of the procoelous seventh cervical of Meiolania from the primitive biconcave seventh cervical as seen in Spoochelys would involve transfer of only one intercentral disc between seventh and eighth vertebrae. The biconcave seventh is absent in turtles other than Spoochelys, primitive pleurodires and chelids. This analysis shows that the procoelous seventh of Meiolania is correlated with development of the procoelous eighth from the biconvex condition.

96.Eighth cervical articulation: 0 = biconcave; 1 = opisthocoelous or procoelous; 2 = biconvex (Gaffney 1985, 1996; Shaffer et al. 1997; Brinkman and Wu 1999; Gaffney et al. 1998; Gaffney et al. 2007; Joyce 2007). Morphology, distribution and homoplasy: The biconvex eighth occurs in chelids and is inferred for Platychelys and Notoemys. It also occurs in the Lightning Ridge taxa, Otwayemys, Mongolochelys, Dracochelys, Ordosemys and Sinemys (Gaffney et al. 1998; Brinkman and Peng 1993; Sukhanov 2000; Brinkman 2001). Gaffney (1996, 1998) asserts that the procoelous eighth of Meiolania developed from the eucryptodiran biconvex condition, implying redevelopment of the massive diapophyses and adjustment of central articulations in four posterior cervicals. The procoelous eighth of Meiolania is more parsimoniously developed from a biconvex eighth adjoining a biconcave seventh, as in Spoochelys and primitive pleurodires. Restricted distribution of the biconvex eighth and its absence in basal centrocryptodires suggests that its occurrence in cryptodires is derived (Shaffer et al. 1997: 260) and not homologous with the biconvex eighth of the Australian turtles.

97. Posterior central articulations at rear of cervical series (New): 0 = wide, subcircular or oval; 1 = narrow, laterally compressed, or triangular (Vaillant 1879; Williams 1950; Hoffstetter and Gasc 1969; Gaffney 1985, 1990; Fernandez and de la Fuente 1994; Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001).

194 Morphology, distribution and homoplasy: Primitively, central articulations are subcircular or oval. Cervical centra tend to be laterally compressed in pleurodires, creating ‘a vertical axis of rotation’ around cylindrical central condyles that facilitate lateral movement (Hoffstetter and Gasc 1969). Tall triangular articulation facets, acuminate ventrally, are a pronounced feature of rear cervicals in the Lightning Ridge taxa and the Pleurodira.

98. Cervical ribs: 0 = present; 1 = absent (Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007; Sterli 2008).

99.Cervical ribs, size and shape: 0 = large; 1 = very large and paddle-like (Gaffney 1996; Gaffney et al. 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: Cervical ribs are present in Proganochelys but not in Palaeochersis (Sterli et al. 2007), and the large, paddle- shaped, curved cervical ribs of meiolaniids are unique (Fig. 41). Cervical ribs at the rear of the neck are inferred for Spoochelys and Sunflashemys on presence of parapophyses that are larger than those of Meiolania. There is no evidence of secondary development of cervical ribs among turtles.

100. Rear cervicals, deep cavity in neural arch above postzygapophyses (New): 0 = absent; 1 = present (Williams 1950). Morphology, distribution and homoplasy: In Spoochelys, Sunflashemys and chelids (pers. obs.), neural arches of cervicals five, six and seven terminate in tall triangular cavities above the postzygapophyses, and cervical five of Meiolania has a shallower cavity. Absent in Proganochelys, this feature has been reported as absent among turtles generally but is cited as synapomorphic for parieasaurs, a possible turtle outgroup (Lee 1995). Distribution among key basal taxa is unclear, however on current evidence, the derived condition unites Spoochelys and Sunflashemys, and is seen also in chelids.

101. Size of cervical parapophyses (New): 0 = do not extend anterior to central articulation facet; 1 = extend anterior to central articulation facet (Gaffney 1985,

195 1996, 1998; Brinkman and Peng 1993; Brinkman and Wu 1999; Hirayama et al. 2000). Morphology, distribution and homoplasy: Cervical ribs six and seven (and perhaps eight) of Proganochelys are fused to the centra, however the parapophyses or intercentra of anterior cervicals are comparatively small and unossified (Gaffney 1990). Parapophyses are absent in Palaeochersis, but are present in Kayentachelys, Mongolochelys, Xinjiangchelys and some Asian eucryptodires; in these taxa parapophyses have not been reported as being of large size. In Spoochelys and Sunflashemys, parapophyses are uniquely developed, even projecting anterior to the central articulation surface. In Meiolania, parapophyses of cervicals one to three cup the condyles of cervicals two to four, and in posterior procoelous cervicals, parapophyses extend forward of the front central facet, widening the central cotyles and thus increasing the arc of lateral movement (Fig. 41). Data is missing for Proterochersis and the condition in platychelyids is unclear. Chelids however retain cervical parapophyses in the form of small ‘inferolateral tuberosities’ (Lapparent de Broin and de la Fuente 2001; and pers. obs.) and in Chelus fimbriata Boulenger 1889, parapophyses on anterior cotyles of cervicals 6, 7 and 8 are continuous with the articular facet and extend well forward of the centrum (Williams 1950: 531: 12), remarkably similar to those of Meiolania and Sunflashemys.

102. Transverse processes, cervical vertebrae: 0 = middle of centrum; 1 = front of centrum (Gaffney at al. 1991; Brinkman and Peng 1993; Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: Proganochelys exhibits the primitive condition, as in Kayentachelys, paracryptodires and plesiochelyids, Meiolania, the Lightning Ridge taxa and pleurodires except Notoemys, and the derived state appears to be independently developed in crown groups.

103. Cervical postzygapophyses extended posterodorsally on elevated neural arch: 0 = no; 1 = yes (Vaillant 1879; Williams 1950; Hoffstetter and Gasc 1969; Gaffney 1985, 1990; Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001; de la Fuente 2003; Gaffney et al. 2006).

196 Morphology, distribution and homoplasy: Primitively the neural arch is low and wide (Vaillant 1879; Hoffstetter and Gasc 1969; Sterli et al. 2007). In Spoochelys and Sunflashemys, the neural arch is elongate and narrow, placing the postzygapophyses behind the central articulation facet. This high neural arch pedicel is typical of chelids and pelomedusoids (Lapparent de Broin 2000; Lapparent de Broin and de la Fuente 2001; de la Fuente 2003). There is evidence of variable development in meiolaniids and basal pleurodires, however the elongated neural tower is functionally related to lateral neck movement and is absent elsewhere in turtledom.

104. First thoracic articulation facet: 0 = taller than wide; 1 = wider than tall (Rueda and Gaffney 2005). Morphology, distribution and homoplasy: The wide central cotyle of the first thoracic vertebra that is diagnostic for platychelyids (Rueda and Gaffney 2005) is also present in Opalania, Spoochelys, Sunflashemys and Meiolania.

105. First thoracic rib: 0 = very large; 1 = smaller than second thoracic rib (Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1990; 1996; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: The primitive very long first thoracic rib is retained in the Lightning Ridge taxa and Meiolania, and its distribution in other stem groups is extremely limited.

106. First thoracic rib, costal attachment (New): 0 = not fused to overlying costal; 1 = fused to overlying costal (Gaffney 1990, Fernandez and de la Fuente 1994; Gaffney 1996; Gaffney et al. 2006; Joyce 2007). Morphology, distribution and homoplasy: Although single specimens exist showing fusion of the first thoracic rib to the first costal bone in Proganochelys and Meiolania (Gaffney 1990, 1996), Gaffney’s (1990: 122) statement that ‘the second thoracic rib is the first costal rib in all turtles’ infers that absence of a fused costal attachment for the first thoracic rib is the usual (or plesiomorphic) condition. This is reiterated by Joyce (2007) - ‘the first thoracic ribs of all turtles … do not fuse with the overlying costals’; again by Gaffney et al. (2006) - ‘the first thoracic rib has no associated costal bone’; and is soundly reinforced in other literature. The

197 fused condition occurs in Spoochelys, Sunflashemys, Chelycarapookus and Notoemys laticentralis (Fernandez and de la Fuente 1994). In Opalania, only the distal section of the first thoracic rib is known. It is very large and fused with the peripheral bone. On this basis, in the context of the sister-group relationship between Spoochelys, Sunflashemys and Opalania, and considering that most of the Meiolania specimens show the fused condition, Opalania and Meiolania are coded as having the derived state of this character.

107. Tenth thoracic vertebra integrated into sacrum: 0 = no; 1 = yes (Gaffney and Meylan 1988; Gaffney et al. 1991; Shaffer et al. 1997; Hirayama et al. 2000; Lapparent de Broin 2000; Gaffney et al. 2007; Joyce 2007). Morphology, distribution and homoplasy: Central fusion of the tenth thoracic vertebra with the first sacral is regarded as a primary pleurodiran synapomorphy, seen in Proterochersis but not Palaeochersis (Gaffney et al. 1991; Lapparent de Broin 2000; Sterli et al. 2007). The last thoracic centrum is fused with the sacrum in Sunflashemys and apparently in Spoochelys. In Meiolania the thoracico-sacral articulation is an unusual ball-and-socket joint, however as in the Lightning Ridge taxa (LRF771 and LRF463), the proximal section of the first sacral rib is greatly enlarged, suggesting a connection or contact with the transverse process of the tenth thoracic vertebra (Gaffney 1996: 14: 9), morphology distinctly different from Proganochelys (Gaffney 1990: 203: 139A).

108. Tenth thoracic ribs: 0 = osseous attachment to carapace; 1 = osseous attachment to carapace and ilium; 2 = disengaged from carapace (Shaffer et al. 1997; Lapparent de Broin 2000; Gaffney et al. 2006). Morphology, distribution and homoplasy: Contact between the tenth thoracic ribs and the ilium is developed in Palaeochersis (Sterli et al. 2007) and Proterochersis, and with some variation in crown pleurodires. The ribs are apparently disengaged from the carapace in Meiolania. Data is missing for Spoochelys and Sunflashemys. The tenth thoracic ribs are usually free in cryptodires (Gaffney et al. 2006).

109. Sacro-caudal vertebra (last sacral integrated with first caudal) (New): 0 = absent; 1 = present (Hoffstetter and Gasc 1969; Gaffney 1996).

198 Morphology, distribution and homoplasy: The central articulation between the last sacral and the sacro-caudal is variably fused in Spoochelys, Sunflashemys and Meiolania. Transverse processes of the sacro-caudal attached distally by ligaments to the last sacral rib in Meiolania, and probably also in the Lightning Ridge taxa. Morphological assimilation of sacral and caudal vertebrae is a pleurodiran feature (Hoffstetter and Gasc 1969) also seen in Proterochersis, Platychelys and Notoemys zapatocaensis (Fraas 1913: 24: 5; Rueda and Gaffney 2005). In these taxa, the fourth vertebra in the sacrum can be described as a sacro-caudal. Sacral-caudal integration is not reported for Palaeochersis although transverse processes are massively developed.

110. Anterior caudal centra (New): 0 = amphicoelous; 1 = opisthocoelous; 2 = procoelous (Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: Vertebral articulations are amphicoelous primitively. In Spoochelys, the front central facet of the sacro-caudal is flattish, differing very little from that of Proganochelys, and the rear articulation is concave. The second caudal (or first ‘true’ caudal) is opisthocoelous. The same condition pertains in Meiolania, and the first caudal is opisthocoelous in Notoemys zapatocaensis and Platychelys (Rueda and Gaffney 2005). The biconcave caudal of primitive Asian eucryptodires such as Ordosemys is positioned more distally in the caudal series and is preceded by procoelous caudals (Brinkman and Peng 1993; Hirayama et al. 2000). Data is missing for key basal taxa but on current evidence, opisthocoely of anterior caudal vertebrae occurs only in platychelyids and meiolanoids.

111. Caudal articulations: 0 = unformed; 1 = predominantly opisthocoelous; 2 = mixed procoelous/opisthocoelous or predominantly procoelous (Gaffney and Meylan 1988; Gaffney et al. 1991; Gaffney 1996, 1998; Shaffer et al. 1997; Brinkman and Wu 1999; Lapparent de Broin 2000; Hirayama et al. 2000; Joyce 2007). Morphology, distribution and homoplasy: The fossil record for basal pleurodires is meagre, however amphicoelous, opisthocoelous and procoelous caudals are known in Platychelys and Dortoka (Lapparent de Broin 2000) and a mixed series is

199 present in Notoemys laticentralis (Lapparent de Broin 2000) and N. zapatocaensis (Rueda and Gaffney 2005). This suggests complex articulation arrangements were antecedent to the fully procoelous condition of chelids and pelomedusoids, and crown cryptodires. The fully or predominantly opisthocoelous tail is synapomorphic for Spoochelys, Sunflashemys and Meiolania.

112. Chevrons: 0 = present on nearly all caudals; 1 = absent or only poorly developed along the posterior caudals (Gaffney et al. 1991; Gaffney 1996; Brinkman and Wu 1999; Hirayama et al. 2000; Joyce 2007; Sterli et al. 2007; Sterli 2008).

113. Caudal ossifications (tail club): 0 = present; 1 = absent (Gaffney 1990, 1996, 1998; Joyce 2007). Morphology, distribution and homoplasy: Proganochelys and meiolaniids uniquely possess caudal ossifications (tail club or rings), structures unknown in any hypothetical turtle outgroup and absent in all other turtles. Palaeochersis does not have a tail club despite the massive transverse processes, so the tail was ‘very wide and low’ and dermal ossifications are present (Sterli et al. 2007). Similar large transverse processes in Spoochelys and Sunflashemys are compelling indirect evidence of a vigorous tail scudding or swinging capability, if not caudal ossifications of some sort. Although the tail club was interpreted as apomorphic for meiolaniids (Gaffney 1996), it is concordant with a variety of primitive features in the group and is coded here as homologous with that of Proganochelys.

Appendicular and podial skeleton 114. Cleithra: 0 = present; 1 = absent (Gaffney et al. 1991; Rougier et al. 1995; Gaffney 1996; Shaffer et al. 1997; Brinkman and Wu 1999; Hirayama et al. 2000; Sukhanov 2006; Joyce 2007; Sterli 2008).

115. Cleithral ventral structure (New): 0 = single transverse base; 1 = separate paired bases. Morphology, distribution and homoplasy: Large cleithra are present in Proganochelys, Palaeochersis, Proterochersis (Lee 1996) and Indochelys (pers. obs.). In Proganochelys and Palaeochersis (Sterli et al. 2007), the base is a stout

200 undivided bar across the front of the plastral lobe that includes the anterior entoplastron. This is also the condition in Meiolania, and although the cleithra lack osseous connection to the carapace, Meiolania retains the primitive articulation between cleithra and acromion (Gaffney 1996; pers. obs.). Cleithral bases are separate in Kayentachelys (Joyce 2006), Heckerochelys (Sukhanov 2006) and Mongolochelys (Sukhanov 2000). The anterior plastral lobe is not preserved in the Lightning Ridge taxa but NMVP186048, an isolated entoplastron from Cape Otway, suggests that reduced cleithra may be present in at least one of the Victorian turtles (pers. obs.) and in Chelycarapookus. Other taxa in this analysis are scored according to Joyce (2007) who cautions that absence of cleithra cannot be assumed for many fossil taxa.

116. Acromial process (New): 0 = triradiate in section and short; 1 = triradiate in section and long; 2 = not triradiate in section (Joyce 2007). Morphology, distribution and homoplasy: This character amplifies that of Joyce (2007; ‘Scapula B’) which refers only to the anteromedial ridge of the acromial process. This redefinition incorporates additional acromial features. The short, strongly triradiate acromial process is the primitive condition (Proganochelys and Palaeochersis). The process is longer, retaining the acromial ridge and triangular cross section in Kayentachelys, Mongolochelys (Joyce 2007), Meiolania and Spoochelys. The acromion is not preserved in Proterochersis, but on the basis of cleithral structure, this element in Proterochersis is probably strongly triradiate, inferring independent development of the slender acromion in crown groups. The intermediate condition unites Spoochelys, meiolaniids, Kayentachelys and Mongolochelys.

117. Coracoid foramen: 0 = present; 1 = absent (Gaffney et al. 1991; Rougier et al. 1995; Hirayama et al. 2000; Gaffney et al. 2007; Joyce 2007).

118. Acromion, distal section with posterolateral spike (New): 0 = absent; 1 = present. Morphology, distribution and homoplasy: Bony enclosure of the coracoid foramen is known only in Proganochelys and Palaeochersis. In advanced turtles, the coracoid foramen is widely open, an acromiocoracoid ligament links the coracoid

201 and acromion, and the coracoid is capped by the epicoracoid cartilage (Walker 1973). Spoochelys has a prominent acromial spike directed towards the medio- distal rim of the coracoid and Meiolania exhibits a similar spike in association with a huge semicircular plate-like coracoid (pers. obs.) as shown in AMF6110 (Gaffney 1996: 22: 17) although not illustrated elsewhere or documented. The acromion of Sunflashemys is more derived, perhaps as an aquatic specialization. Data is missing for key basal taxa but the unique acromial spike is known only in Spoochelys and meiolaniids and the condition appears to be primitive relative to groups other than Proganochelys and Palaeochersis.

119. Olecranon process of ulna (New): 0 = low to medium in height; 1 = very high (Gaffney 1990, 1996; Sterli et al. 2007). Morphology and distribution: The olecranon process in Proganochelys is higher than in other turtles (Gaffney 1990) but not as pronounced as in Palaeochersis, Spoochelys, Sunflashemys and Meiolania (Gaffney 1996; pers. obs.). In these taxa, the humeral articulation surface (sigmoid notch) is deeply curved, unlike the condition in most turtles in which the articular surface is flattish (Gaffney 1990). This indicates robust cohesion between ulna and radius, a characteristic of terrestrial forms (Gaffney 1990; 1996). Data is missing for basal taxa, but at present the prominent olecranon is known only in Palaeochersis, Spoochelys, Sunflashemys and the meiolaniids.

120. Dorsal ridge of proximal ulna shaft (New): 0 = weak to medium development; 1 = very pronounced (Gaffney 1990, 1996). Morphology, distribution and homoplasy: The proximal ulna shaft of Proganochelys bears a pronounced dorsal ridge, absent in turtles apart from Spoochelys, Sunflashemys and Meiolania. In the Australian taxa, the ridge creates a deep dorsomedial trench and subtriangular proximal articular surface. Strong development of this feature in Meiolania is suggested as a meiolaniid synapomorphy by Gaffney (1996). The ridge is apparently absent in Palaeochersis (Sterli et al. 2007). The heavy dorsal ridge of the ulna unites Spoochelys, Sunflashemys and meiolaniids. Data is missing for key basal groups, but the feature is absent in advanced turtles.

202 121. Connection of pelvis to carapace and plastron: 0 = ligamentous; 1 = partly sutured; 2 = fully sutured (Gaffney and Meylan 1988; Gaffney et al. 1991; Rougier et al. 1995; Shaffer 1997; Gaffney 1996, 1998; Hirayama et al. 2000; Lapparent de Broin 2000; Joyce 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: Although exact homology and phylogenetic significance of the morphology is contentious (Gaffney et al, 2006), the pelvic girdle of Palaeochersis resembles that of Proterochersis in many features and is at least partially sutured to the carapace and plastron (Lapparent de Broin 2000, and pers. commun.; Marcelo de la Fuente pers. commun.; Lapparent de Broin et al. 2004; Sterli et al. 2007). In Palaeochersis, the iliac blade is sutured to the carapace on the last costal and peripheral bones, as in Proterochersis and Platychelys; the anterolateral process of the pubis is well developed as in Proterochersis but incompletely attached to the xiphiplastron (Sterli et al. 2007); and the posteromedial transverse section of the ischia is sutured to the posterior plastral lobe. In this analysis, coding of Palaeochersis as transitional for this character is underpinned by supplementary evidence of ‘proto-pleurodiran’ affinities: elliptical supramarginal scales; rounded carapace front extending anteriorly; tight curvature of the elongated axillary buttress and semicircular pygal notch. These shell features are also pronounced in Proterochersis, in which pelvic fusion is further advanced. Meiolaniids have been scored previously as lacking pelvic fusion, however the derived condition in Niolamia cannot be discounted. The type skull of Niolamia was associated with a carapace section including the last vertebral scute, costal and three peripherals (Woodward 1901; Gaffney 1996). Thin costals, absence of costo-peripheral fontanelles, deeply rounded scute sulci and ‘large triangular prominences’ bordering the peripherals indicated a primitive meiolaniid. In addition, there was an ’expanded upper end of the relatively small left ilium fused with a costal bone’ showing ‘Miolania [sic] … to have been Pleurodiran in the fixation of its pelvis’ (Woodward 1901: 173). Sadly, this material is missing (Marcelo de la Fuente pers. commun. 2006). Meiolaniids are thus scored ‘?’ in this analysis. Spoochelys and Sunflashemys are coded as transitional – Spoochelys has a vertical ilium and slightly bifid xiphiplastron with thickened ischial base; and a suprapygal with part of a deep irregular pit for the ilium, resembling the chelid condition, is known for Sunflashemys. First seen in

203 Proterochersis, full sutural connection between shell and pelvis is an unambiguous pleurodiran synapomorphy in most cladistic analyses (Gaffney et al 2006).

122. Ventral ischial tubercle: 0 = present; 1 = absent (Rougier et al. 1995; Joyce 2007; Sterli et al. 2007; Sterli 2008).

123. Hypoischium: 0 = present; 1 = absent (Gaffney 1990; Rougier et al. 1995; Hirayama et al. 2000; Gaffney et al. 2007; Joyce 2007; Sterli et al. 2007; Sterli 2008).

124. Phalangeal formula: 0 = most digits with two short phalanges; 1 = most digits with three long phalanges (Gaffney 1990; Rougier et al. 1995; Hirayama et al. 2000; Joyce 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: The digital formula for Proganochelys is 22222 and 22221 for meiolaniids. Stocky phalanges and low phalangeal count were interpreted by Gaffney (1990) as independently acquired in each taxon, but clearly presence of a similar 22221 formula in Palaeochersis (Rougier et al. 2000) indicates that possession of two short broad phalanges in most digits is the primitive state for turtles. Phalangeal count in the smaller Lightning Ridge taxa is uncertain, however the very short, broad digits agree closely with those of Proganochelys and Meiolania. Data is missing for many basal taxa but phalanges are relatively short in Notoemys laticentralis (Fernandez and de la Fuente 1994). The derived condition is seen in Mongolochelys and crown groups.

125. Reduction or loss of fifth digit phalanges: 0 = no; 1 = yes (Gaffney 1996; Rougier et al. 1995; Joyce 2007; Sterli et al. 2007; Sterli 2008). Morphology, distribution and homoplasy: Distribution of this character among more derived taxa is unclear and data is missing for many basal turtles. Reduction or loss of fifth digit phalanges is a diagnostic feature for Palaeochersis that is also present in Meiolania. Fifth digit phalanges are retained in Notoemys laticentralis and Araripemys (Meylan 1996). As far as is known, the derived condition occurs only in Palaeochersis and the meiolaniids.

204 Discussion PAUP analysis produced 3510 shortest trees, of 347 steps each. The trees have a Consistency Index of 0.4669 (CI of 0.4543 excluding uninformative characters), a Homoplasy Index of 0.5331 (HI excluding uninformative characters of 0.5457), Retention Index of 0.7123 and Rescaled Consistency Index of 0.3325. The strict consensus and 50% majority rule consensus are similar, however the latter was slightly better resolved.

The analysis confirms Proganochelys as sister taxon to all other turtles and unites Proterochersis and australochelyids in a Triassic-Early Jurassic clade. Other taxa in the matrix are separated into two major groups that are primarily northern and southern hemisphere divisions. In both the strict and 50% majority rule consensuses, Proterochersis and australochelyids are united on four unequivocal synapomorphies, one of which, shape of the anal notch, has a CI of 1.00. A partial degree of pelvic fusion is inferred as either plesiomorphic for turtles other than Proganochelys (ACCTRAN optimization), or apomorphic in Palaeochersis (partial fusion) and Proterochersis (full sutural connection). Either way, the sutural condition in platychelyids, chelids and pelomedusoids is given as convergent.

Turtles other than Proganochelys, Proterochersis and australochelyids are united by five unequivocal synapomorphies each with a CI of 1.00. These are loss of the lacrimal bone and anal notch, development of the single vomer, the acute quadrate margin and a weak inferior parietal process.

Indochelys, Chubutemys, Tertiary meiolaniids, Early Cretaceous taxa from New South Wales and Victoria (excluding Otwayemys) are united in a monophyletic ‘austral’ or Gondwanan clade, below Condorchelys and Kayentachelys. This group is supported by the circular nuchal articulation with the eighth cervical vertebra and loss of inframarginals, and seven synapomorphies with a CI of 1.00 (according to ACCTRAN optimization), including fusion of cranial scute and bone, derived features of epipterygoid and lower jaw, atlantal fusion, development of formed cervical articulations, opisthocoelous caudal articulations and dorsal ridge of proximal ulna shaft. Within this clade, Indochelys and Chelycarapookus are united by the elongated epiplastra.

205 NMVP199057 (the partial carapace and plastron from Inverloch, Victoria), Chubutemys, the Lightning Ridge taxa and Tertiary meiolaniids form an unresolved polytomy, weakly supported by the broad vertebral scutes, a reversal from the ‘very broad’ state. The Lightning Ridge taxa and meiolaniids form a monophyletic clade on a suite of synapomorphies, including the crescent-shaped interpterygoid vacuity (CI of 1.00), broad basisphenoid exposure, the circular supratemporal separated from the temporal margin, contact of splenial and dentary in the meckelian sulcus and high vaulted carapace.

According to this analysis, the biconvex fourth and eighth cervicals of Early Cretaceous Australian taxa and Chubutemys are not homologous with those of primitive northern hemisphere eucryptodires, but the procoelous eighth of Meiolania may be a reversal of the biconvex state, corresponding with alteration of the biconcave seventh that is seen in the Lightning Ridge taxa.

The three Lightning Ridge meiolanoids are united by the extended basisphenoid edge of the open cavum labyrinthicum, narrow costo-vertebral tunnel, tall central facets and posterior position of the postzygapophyses in rear cervicals, and central fusion of the tenth thoracic vertebra with the sacrum (possibly homoplasic with the pleurodiran condition).

Closure of the lacrimal duct, loss of the supratemporal and caudal ossifications, subdivision of the cleithral base and increased phalangeal count separate the predominantly ‘boreal’ clade from the southern groups. Condorchelys is positioned below Kayentachelys in this analysis. The branch separating Heckerochelys and other northern groups is supported by dorsal relocation of the canalis cavernosus and basicranial transitions related to caudomedial pterygoid extension below the prootic and cavum labyrinthicum.

At the base of this clade, Otwayemys and Mongolochelys are united by three unequivocal synapomorphies involving transformation of unformed to formed central articulations in cervicals four, seven and eight. This may be unreliable given that 78% of data is missing for Otwayemys and the fifth vertebral articulation of

206 Otwayemys may be procoelous rather than biconcave. It does infer however that the biconvex eighth of Otwayemys may not be homologous with that of sinemydid- macrobaenids. Affinities remain unclear: resolution of Otwayemys as sister-clade to Mongolochelys from Asia is inconsistent with phylogenetic and biogeographic evidence for other south-east Gondwanan biota.

Otwayemys and Mongolochelys are resolved as sister taxa to a paraphyletic group formed by Kallokibotion, , Paracryptodira, , Ordosemys, Cryptodira, Asian eucryptodires and Pleurodira successively. Notwithstanding the plethora of apparent panpleurodiran and pleurodiran features in the Lightning Ridge taxa and meiolaniids, the majority rule consensus obtained in this analysis separates Proterochersis and the Australian groups from the Pleurodira. The topology places Jurassic platychelyids and Pleurodira as descendents of the Asian eucryptodires, including Early and Late Cretaceous taxa; and Hangaiemys, Sinemys and Dracochelys are within the Cryptodira. Stratigraphic incongruity, supposed redevelopment of a lost bone element (mesoplastra) in platychelyids, and multiple reversals along the branch between Dracochelys and Pleurodira suggest that this section of the tree is seriously flawed. Changes involve jaw trochlear structures, basicranial arterial foramina and flooring of the inner ear and recessus scalae tympani, and imply that the processus trochlearis pterygoidei and separation of the facial nerve from the canalis cavernosus evolved independently in meiolanoids and pleurodires. The cladogram also infers that a predominantly lateral mode of neck retraction developed twice in turtles.

This result in which features that usually support monophyly of the Pleurodira appear as derivatives of cryptodiran structures resembles phylogenies obtained by Dryden (1988), Sukhanov (2006), Joyce (2007) and Sterli (2008). For reasons similar to those argued by Joyce (2007) against results of his preliminary unordered and unweighted analyses, this outcome in relation to the Pleurodira is regarded as unsound due to stratigraphic conflict and ‘morphological long-branch attraction’, that is, systematic homoplasy that unites convergent lineages (ibid., 2007). This present analysis is heuristic and resolution is flimsy, as demonstrated by the decay analysis. In the strict consensus, the vast majority of support values are <50% and therefore not indicative of support. The decay index or Bremer support shows the

207 lowest possible value for nodes other than Chelidae + Pelomedusoides. Only one extra step is required for all other nodes to lose resolution and collapse into multichotomies.

Gaffney et al. (2007) stressed that missing data for Chubutemys and Otwayemys was probably masking contradictory characters. Shaffer et al. (1997: 251; after Huelsenbeck 1991) emphasize that ‘very incomplete fossils will lead to multiple most-parsimonious trees and therefore greater uncertainty about particular nodes’ and inevitably ‘a fossil’s ability to improve the resolution of a tree increases with completeness of the fossil and temporal proximity to its ancestral node’. The Lightning Ridge taxa are relic groups, and although better known than Chelycarapookus and Otwayemys (86% and 78% missing data respectively), 23% of data is missing for Spoochelys, 56% for Sunflashemys, and 90% for Opalania. In fact in this analysis, half the data is missing for more than half the taxa. PAUP fills in missing characters as consistent with the most parsimonious cladogram. Missing data and the need for finessing of characters for basal pleurodires and cryptodires are serious underlying deficiencies that can only be remedied by more detailed comparison with overseas material, discovery of further articulated specimens from New South Wales and Victoria, and new fossil material for Early Mesozoic turtles generally.

The relationship between Triassic-Jurassic turtles and the Australian taxa clearly demonstrates the archaic nature of presumed meiolaniid autaopomorphies such as the deep quadratojugal cheek flanges, ‘nasomaxillary sinus’ (lacrimal duct), B- scale horn sheath (supratemporal), cranial scute pattern, tail club and ‘intrapterygoid slit’ or interpterygoid vacuity. In meiolaniids, the interpterygoid vacuity persisted as the pterygoid moved backwards below the inner ear, while in cryptodires, the vacuity closed prior to development of the posteromedial pterygoid extension. In meiolaniids, structures associated with flooring of the inner and middle ear, basicranial arterial and nerve pathways and cervical articulation patterns are not homologous with those of cryptodires or eucryptodires.

Basicranial structures in Spoochelys and Sunflashemys are most similar to Notoemys. New skull material of the meiolaniid cf Warkalania from Riversleigh

208 reinforces evidence of pleurodiromorph affinities, illustrating transitions between the Mesozoic meiolanoids and the Meiolaniidae. As in all meiolanoids, the pterygoid posteromedial extension is not sutured to adjacent sections of the primary neurocranium. The canalis nervi facialis is deeply separated from the canalis cavernosus (a primary pleurodiran synapomorphy), opening into the cavum acustico-jugulare as in Notoemys and Emydura.

Apart from pleurodire-like basicranial and shell features, evidence is compelling of a lateral mode of neck retraction in the Lightning Ridge meiolanoids. According to this analysis, the biconcave seventh cervical of Early Cretaceous Australian taxa is not homologous with that of platychelyids and chelids, and the biconvex fifth cervical of platychelyids and chelids did not develop from the biconvex fourth of the Australian taxa. Nonetheless, apart from the biconvex fifth cervical, significant derived chelid-like features were in place in the Australian groups, and it is tempting to speculate that development of the biconvex fifth marked the advent of the predatory, outwardly-directed strike action in basal side-necked forms.

A diagnosis for Meiolanoidea and revised diagnosis for Meiolaniidae are proposed. Gaffney (1996) erected but did not define the suborder Meiolanoidea, here given the new rank of Superfamily.

SYSTEMATIC PALAEONTOLOGY Order TESTUDINES Batsch 1788 Superfamily MEIOLANOIDEA Gaffney 1996, new rank

Diagnosis. Comprises Spoochelyidae (Spoochelys, Sunflashemys, Opalania), Chelycarapookidae (Chelycarapookus) and Meiolaniidae (Niolamia, Ninjemys, Warkalania, Meiolania and Crossochelys). Primitive terrestrial and semi-aquatic freshwater turtles. Early Cretaceous – Holocene (New South Wales, Victoria, Lord Howe Island and New Caledonia) and Early Cretaceous – Eocene (Argentina). United by common possession of: cranial scute pattern of scale X (primitively) and scutes G, D, B, C, H, E, J, K and I (as in Meiolania; Gaffney 1983, 1996, 1998); supratemporal separated from margin of temporal fossa; processus inferior 209 parietalis weakly developed, contacts epipterygoid and prootic above trigeminal foramen; epipterygoid triangular, wide at base, extending ventral to basisphenoid rostrum, with anterolateral flange into subtemporal fossa; foramen nervi trigemini formed by prootic and epipterygoid; epipterygoid forms rear margin of fossa interorbitale; wide bracket-shaped interpterygoid vacuity; large canalis cavernosus, bean-shaped in section, opening ventral to fenestra ovalis; canalis nervi facialis floored by pterygoid, roofed by prootic and separated from canalis cavernosus, with long posterior extension opening into cavum acustico-jugulare; pterygoid separated from posterolateral of basisphenoid and anterolateral of basioccipital; primitively, hypoglossal nerve foramina in suture between exoccipital and basioccipital; contact of splenial and dentary in meckelian sulcus anterior to foramen intermandibularis medius; circular nuchal tubercle for articulation with eighth cervical vertebra; inframarginals absent; mesoplastra absent; biconvex fourth cervical vertebra; tuberculum facets of sixth cervical vertebra anterior to centrum with parapophyseal lamina covering almost half length of centrum; first thoracic rib very large and fused with strongly reduced second thoracic rib; anterior thoracic vertebrae V-shaped in section with straight ventral edge; caudals fully opisthocoelous; primitively, coracoid foramen present but open (acromial spike and broad flaring coracoids – Spoochelys and Meiolania); strong proximodorsal ridge on ulna creating subtriangular proximal articulation.

Meiolanoids share with australochelyids: histological unity of bones and scutes of the temporal roof; very large nasals; top of external nares level with top of orbit; narial platform or bulge; shallow maxilla below orbit; deep cheek flanges formed by jugal and quadratojugal; vertical curtain of bone partly closes rear temporal fossa (Niolamia and Meiolania); rounded carapace front extending well forward; supramarginal scales along anterolateral of carapace (Spoochelys and possibly Meiolania); shell and pelvis partially sutured (Spoochelys and Sunflashemys); overlap facets developed as ventrolaterally directed tubercles on proximal articulations of metatarsals; digital formula 2222?.

Meiolanoids share with Proterochersis, platychelyids and Pleurodira: hyomandibular branch of facial nerve separated from canalis cavernosus and opening into cavum acustico-jugulare; canalis nervi facialis roofed by prootic,

210 primitively; bifid basisphenoid; processus trochlearis pterygoideus (Meiolania and Pleurodira); fenestra ovalis open ventrally, margins formed by prootic, opisthotic, basisphenoid and basioccipital (as in Notoemys); roof of carotid artery posterior to foramen caroticum basisphenoidale formed by basisphenoid or basisphenoid and prootic (Notoemys, Spoochelys and Sunflashemys); carotid artery unfloored primitively or partly floored by pterygoid; high-domed carapace (primitively); rounded carapace front extending well forward (primitively); cervical scute wide, prominent and tuberous (primitively); domed elliptical supramarginal scales on anterolateral edge of carapace (primitively); first vertebral scute with curved semicircular anterior margin (primitively); bowl-shaped nuchal (primitively); first thoracic rib fused with first costal; long transverse tubercle on first thoracic rib for scapula articulation (as in platychelyids); axillary buttress unthickened, very elongated and tightly curved; bifid xiphiplastron (Spoochelys); formed cervical articulations; fusion of atlantal central elements (Meiolania and Pleurodira); seventh cervical biconcave primitively (Spoochelys and chelids); tall neural pedicle on rear cervicals; diapophyses large, triangular at mid-centrum; first thoracic vertebra wider than tall (as in platychelyids); variable central fusion of last sacral with first caudal (forming one sacro-caudal vertebra as in Proterochersis).

Family MEIOLANIIDAE Gaffney 1996

Revised diagnosis: Niolamia, Crossochelys, Ninjemys, Warkalania and Meiolania. Early Cretaceous – Holocene of Australia, Lord Howe Island and New Caledonia; Late Cretaceous – Eocene of Argentina. Short wide face; adults usually with cranial and shell sutures fused. Uniquely possessing - supratemporal and rear temporal roof margin produced into posteriorly and laterally directed processes; supratemporal (scale B) with underlying horn or boss; three scale areas (A, B, C of Gaffney, 1983; 1996) tuberous; basipterygoid fissure separates pterygoid caudomedial extension from posterolateral surface of basisphenoid and anterolateral surface of basioccipital. Temporal emargination completely absent, related to presence of postparietal, large squamosal and relatively small parietal; reduced lacrimal duct formed by nasal and maxilla lateral to and communicating with apertura narium externa (determinable only in Meiolania and Ninjemys); nares divided by premaxilla and nasals; broad squamosal/quadratojugal contact ventral to 211 completely enclosed incisura columellae auris of quadrate (absent in Niolamia); crescent-shaped interpterygoid vacuity; thin palate concave ventrally with variable parasagittal perforations and vomerine ridge on midline; processus trochlearis pterygoidei without posterodorsal flange (Meiolania); carapace-plastron attachment ligamentous; axillary and inguinal buttresses unthickened and not reaching costals; pleating or overlap of scutes of anterior carapace margin; posterior peripherals scalloped; mesoplastra absent; inframarginals absent; plastron with irregular fontanelles on midline (known only in Meiolania); first thoracic vertebra facing anteriorly; first thoracic rib fused to carapace, deep, blade-like and reaching plastron; tenth thoracic rib disengaged from carapace; cervical central articulation formula (2((3((4))5))6))7))8I; large paddle-shaped free cervical ribs present on cervicals 2-6, in Proganochelys cervical ribs 2-5 are free; parapophyses are incorporated into central articulations of cervicals 5, 6, 7; cervical ribs reduced posteriorly; caudals fully opisthocoelous with strong haemal keels; tail partially or completely surrounded by dermal ossifications; tail club formed by fusion of terminal caudal vertebrae and osteoderms (at least in Ninjemys oweni and Meiolania platyceps); cleithral base single, cleithra contact acromial process; fifth digit phalanges absent. Meiolania platyceps: cavum tympani hypertrophied, front of otic chamber ballooned; trilobial cavity in roof of cavum cranii.

Meiolaniids share with australochelyids: vertical curtain of bone partly closing rear temporal fossa; very large nasal bones; high dorsal limit of external nares (as in Australochelys); narial platform or bulge; smooth palate; maxilla very narrow below orbit; deep cheek flanges formed by jugal and quadratojugal; eighth cervical vertebra with very large transverse processes (as in Palaeochersis).

212

CHAPTER TEN

THE LIGHTNING RIDGE FOSSIL FLORA AND FAUNA – A DIVERSE HIGH-LATITUDE, WARM CLIMATE BIOTA FROM EARLY CRETACEOUS AUSTRALIA

This chapter presents a comprehensive account of the Albian fossil biota of Lightning Ridge, New South Wales. Information herein is based primarily on fossil assemblages sampled from 40 ‘spot locations’ or microsites widely dispersed across the opal fields. Fossil and opal diagenesis, collection biases, depositional conditions, taphonomy, the fossil flora and fauna, palaeoclimate, palaeoecology and palaeogeography are examined. This provides a contextual background to the turtle fauna. Palaeoecology and biogeography of the turtles are discussed in Chapters Eleven and Twelve.

Sampling was opportunistic, so the aims of the survey were simply to examine taxonomic diversity, spatial extent and taphonomic implications of the fossils, and any differences arising between samples from different areas; and to test the fidelity of opal miners’ samples against those made by palaeontologists. Survey data, microsite assemblages, collection methods, location maps and a list of fossil taxa are presented in Appendices 2.0 and 3.0.

At palaeolatitude of 65o-70oS, lying between Early Cretaceous freshwater sites of southern Victoria and freshwater and marine sites in Queensland, Lightning Ridge is a near-polar location. Several thousand vertebrate bone elements are now held publicly and privately, a yield comparable with that of the Alaskan Colville River location, the most prodigious near-polar dinosaur locality (Rich et al. 1997, 2002; Rich and Vickers-Rich 2000).

216 Opalised fossils were encountered from the earliest days of opal mining in New South Wales. Opal workings at White Cliffs predate those at Lightning Ridge and other fields (Cram 2004) and produced the first opalised specimens (Jaquet 1893; Etheridge 1897, 1904). References to opalised fossil material from Lightning Ridge appeared in the Walgett Spectator of 1906; and in the early 1900’s, important pieces were shipped to the British Museum, London. Throughout the last century, countless specimens were destroyed or sent overseas to private collectors, and no doubt most with any gem potential were obliterated on the lapidary wheels. Geological and newspaper reports and popular publications merely hint at the scale of loss (Idriess 1940, 1967; Leechman 1961; Lloyd 1967; O’Leary 1977; Aracic 1979; Cram 2004) and there is overwhelming circumstantial evidence of a magnitude of destruction that is truly appalling (Smith and Smith 1999a). This situation persists even today, despite export restrictions and increasing public awareness of the scientific value of these remarkable items.

Little interest was shown by palaeontologists until the late 1970s, when Ralph Molnar of the Queensland Museum, Brisbane, recognized the significance of the locality. Important discoveries and publications followed – on lungfish (Kemp and Molnar 1981), crocodiles (Molnar 1980; Molnar and Willis 2001), (Molnar and Galton 1986; Molnar 1996), birds (Molnar 1999), monotreme mammals (Archer et al. 1985; Flannery et al. 1992) and a possible (Clemens et al. 2003). The first attempt to describe the locality (Smith and Smith 1999a) is superceded by new research and new specimens. Several recent publications focus on molluscs - Hocknull (1997, 2000), Hamilton-Bruce et al. (2002, 2004), Kear et al. (2003), Hamilton-Bruce and Kear (2006), Kear and Godthelp (2006) and Kear (2006). Musser (unpubl. 2005) reviewed the Lightning Ridge .

Horizon and age Opal-bearing sediments of the Australian opal fields are progressively younger towards the north-east of the continent, ranging from around 122 to 91 million years (Horton 2002). Thus the South Australian fields of Andamooka, Coober Pedy, Stuart Creek and Lambina (, Maree Subgroup) are -Early Albian; the Doncaster Member at White Cliffs is Late Barremian-Aptian; and the

217 Queensland fields of Winton, Yowah and Opalton (Winton Formation) are Cenomanian.

At Lightning Ridge, opalised fossils occur in the Finch Clay Facies of the Wallangulla Sandstone Member (Bourke 1973; Holmes and Senior 1976; Byrnes 1977; Watkins 1985). Outcropping over vast areas of northwestern New South Wales and southern Queensland, extending to depths of 300-480 metres (Exon and Senior 1976), the Griman Creek Formation is included in the Early Cretaceous Rolling Downs Group with the Doncaster and Coreena members of the and the Surat Siltstone (Senior et al. 1977; Burger 1986, 1995; Senior 1996; Frakes et al. 1987; Cook and McKensie 1997).

Dating for the Griman Creek Formation is not precise. It is middle-Albian on foraminiferal evidence (Scheibnerova 1983, 1984). On palynological evidence, it is middle- to late Albian (Morgan 1984; Dettman et al. 1992) or early to middle Albian (Burger 1980); and late Albian on a combination of palynology and biostratigraphy (McKellar, J. L. In Press. Cited by Horton 2002). In the Lightning Ridge district, the Formation is unconformably overlain by Cumborah Gravel (Tertiary), consisting of mixed quartzose sandstones and silcretes (Watkins 1985; Senior and Chadderton 2007).

At depths to more than 30 metres, the Finch Claystone Facies or ‘opal dirt’ consists of fine-grained clays and siltstones occurring as two or more discontinuous lenses or levels from a few centimetres to more than 5 metres thick. These levels are interspersed through the Wallangulla Sandstone. Stratigraphic information is unavailable on these small-scale units, the time differential between shallow and deep levels of ‘opal dirt’ is unknown, and it is unclear whether upper biofacies carry a different fossil fauna from those of deeper levels.

Collection methods Collections discussed in this study were made over a period of more than 25 years by opal miners and the author, from underground and from excavated sediments on the surface. Two important assemblages were excavated under more controlled

218 conditions by Henk Godthelp and colleagues from the University of New South Wales, Sydney.

Opal miners use jack-hammers (or air-picks) or small mechnical ‘diggers’ to extract the claystone, which is brought to the surface by hoist or ‘blower’, a suction machine that propels the claystone through pipes. Opal dirt is left on the surface as mullock, stock-piled, dumped in designated areas or trucked to dams for processing in agitators (cement mixer barrels). As water is pumped into the rotating barrels, opal dirt disintegrates into a slurry that is discharged into silt traps. Tailings are the residue of tonnes of opal dirt, each fresh tailing heap representing one to five or more truckloads. Tailings are sorted for precious opal and are usually left at the dams.

23 of the 40 survey assemblages detailed in Appendix 2.0.2 were collected by the author from opal dirt that was examined and searched during or after the mining process. Specimens were collected direct from subsurface claystone horizons; from excavated mullock or top-dirt; from tailing heaps and silt tanks at the processing dams; and from buckets of rough opal purchased from opal miners. Opal miners’ specimens were usually collected from tailings after mechanical processing of the opal dirt.

Registered mineral claims are generally 50 x 50 metres and opal-bearing sediments are extracted selectively during opal mining. Therefore each sample group derives from a specific site, although in some instances, precise locations are unknown. Several assemblages consist of material collected from ‘clustered’ locations within major palaeochannels (sites 3 and 4; 12; 28 and 29; 31 and 32; 33; 35 and 36). The Kellies One assemblages (31 and 32) were retrieved from two discrete areas within a fossil bed that extends for more than 1000m2 (pers. obs.).

Fossil lithologies extracted during opal mining are completely disrupted, and although engineered to retain every piece of potch and opal larger than about 10 mm, processing machinery destroys and damages an incalculable number of fossil specimens. The term ‘’ used here refers to fossil material >10 mm in size which is usually ignored by the opal miners and ends up in the silt tanks.

219 Most collections at these locations were from sediments disturbed during opal mining, under conditions far from ideal for scientific purposes. Clumsy and unorthodox excavations have supplied hundreds of isolated fragmentary specimens, so sorting of morphotypes and taxa has been laborious and extremely difficult. No doubt, interpretations given here will need revision following future fossil discoveries, more complete preparation of specimens and close examination of comparable overseas material. In the case of isolated elements, taxonomic separations are based on gross morphology, and external and internal bone texture. Distinguishing taxa from scrambled and fragmentary elements can be achieved by cross-referencing, extrapolation and deduction, but despite best efforts, many specimens are too scrappy to be referred with confidence to particular taxa or even to particular groups. Corresponding bone elements in specific mullock heaps, or in tailings or agitator fines from a particular ‘wash’, may have been articulated or associated before extraction. In all likelihood, ongoing research and future fossil finds will lead to revision of identifications as well as new records.

A few comments on search techniques should assist workers on the field. Surface details and contours are obscured when the potch is wet, so ‘tailings’, opal dirt and ‘fines’ should be dried before searching for fossil material. The surface texture of plant material is irregularly striated and pitted, resembling frosted glass, whereas opalised bone is often, but not always, smooth and semi-lustrous.

Materials As mentioned previously, all itemized specimens listed in the sample assortments (Appendix 2.0.2) are in public ownership, either at the Australian Museum, Sydney, or the Australian Opal Centre, Lightning Ridge. Certain material discussed in this chapter is held at the Australian Opal Centre pending imminent donation to that institution under the Cultural Gifts Program. It is anticipated that these specimens will be included among the batch of donations to be processed in June 2009 by the Committee on Taxation Incentives for the Arts, Canberra.

220 Preparation and conservation of opalised fossils Opalised fossils are comprised of potch (common opal lacking colour play) or of precious opal. Both are chemically similar. Opal is non-crystalline (amorphous), fractures conchoidally and is a relatively soft gemstone (5.5 - 6.5 Moh’s scale), however opalised material usually does not require consolidation with chemicals and does not need to be stored in water.

Opal dirt is generally soft and hydroplastic, requiring only wetting and drying before sieving. Detergents, soap or Calgon water softener may speed the separation of clay particles, depending on the types of clays involved. Specimens of claystone with layers of adherent small fossils are cleaned with soft brushes under running water or using a fine air-scribe or water tool. Claystone can be hardened with several coats of water-diluted PVA adhesive (Aquadhere), Paraloid or Acryloid B72. Softer claystone matrix concealing opalised material is easily shifted with a scalpel blade. Some specimens are coated with a hard veneer of white microcrystalline silica, others with iron oxides, or hollandite, which may be removed with a Dremel-type handpiece fitted with very fine diamond points. Specimens must be water-cooled during mechanical preparation because opal fractures (and loses colour play) when heated.

Colours and patterns in the potch and enclosing claystone assist in the realignment and reassembly of shattered bone material. Broken sections are mended or stabilized with Acryloid B72 or Cyanoacrylate (‘superglue’) which readily fills cracks and fissures. These adhesives must be used judiciously, as they fill and conceal bone sulci and sutures. Opal is unaffected by acetone which will reverse over-zealous use of chemical stabilisers.

Opalisation and fossilisation Geological and geochemical factors controlling opal diagenesis are poorly understood (Watkins 2002). Current formation theories are: 1) Deep weathering model (Exon and Senior 1976; Watkins 1984; Senior 1996; Horton 2002; Senior and Chadderton 2007). Free silica, produced during alteration of feldspar and smectite to kaolinite by chemical

221 weathering, is trapped by permeability barriers. Silica sol concentrates in cavities into a gel-like colloid (Jones et al. 1964; Darragh et al. 1966; Darragh and Gaskin 1966), eventually hardening into opal by precipitation and/or evaporation. Based on palaeomagnetic (Idnurm and Senior 1978) and isotope evidence (Bird and Chivas 1993), opalisation resulted from two major weathering events during the late Mesozoic and Cainozoic, perhaps at around 24 Ma (Horton 2002).

2) Syntectonic model (Pecover 1996, 1999, 2003, 2005; Rey et al. 2005). Hydrothermal liquid was forced upwards and cooled to precipitate precious opal. Vertical brecciated zones (‘blows’) were conduits for silica- laden heated fluids that formed hydraulic fractures and deformations under extreme pressure. Liquid silica was deposited explosively, at high temperatures (>50-100oC) during dynamic cyclical events associated with regional tectonic activity during the Tertiary.

3) Mound springs model (Deveson 2004, 2005). Hydrothermally produced silica is injected into cracks and voids by hydraulic pumping caused by seismic or other events, perhaps geyser or mud volcanos. Pressurization causes rupturing of rock units and formation of ‘blows’. Overlying gravels are basement material ejected from deep undergound by exploding mound springs. Cavities were created by leaching of fossils and evaporite minerals, or hydraulic fracturing. Clay or silica gel lining the cavities act as semi-permeable membranes, concentrating and purifying the silica sol. Dialysis of silica spheres in suspension requires an energy input or a counter current of water of lower ionic strength.

4) Cretaceous microbe model (Behr et al. 2000; Behr 2001). Opal silica is a bi-product when acids and enzymes excreted by bacteria cause biochemical weathering of clay minerals and feldspar. Rich microbial communities exist inside host rock and opal, and freshwater aerobic bacteria of Early Cretaceous age occur in Lightning Ridge opal, their biology indicating opal formation in shallow muddy clay/silt lenses of neutral pH with high plant debris content at temperatures of 20-35oC. Temperatures

222 may reach >50oC through intense composting, in ‘bioreactors’ generating carbonic acid, converting smectite to illite plus silica sol. Under this model, opal formed shortly after deposition of the host sediments.

5) Phytolithic model (Dowell and Mavrogenes 1999; Dowell et al. 2003, 2005). Host sediments were formed by meteoric water but oxygen and carbon isotope readings for opal fit neither meteoric nor hydrothermal parameters, indicating that opal is biogenic. Opal is formed when aqueous silicic acid polymerizes as microscopic phytoliths in cell walls, luminas and intercellular spaces in living plants. Phytoliths recycled through leaf litter and/or roots are dissolved by weathering or microorganisms and distributed to lower sediment profiles. Biogenic opal remains in the soil after the plants’ death. Microorganisms in potch and opal play a major role in dissolution and re-precipitation of opal and host silicates, and organic carbon in opal structures formed at the time of diagenesis, only a few thousand years ago (Quaternary, Holocene).

Despite major inconsistencies, Rey et al. (2005) insist that these models are complementary. Understanding of opalised fossil formation is at an early stage, but obviously any model at odds with fossildiagenetic processes is implausible (Smith 2005).

The detrital component of the Finch Claystone is very high and the correlation between centers of silica precipitation, palaeochannels and precious opal has been recognized for many years (Watkins 1985; Senior 1998; Smith 2005). Many of the Coocoran fields produce vast quantities of amorphous opalised material comprised entirely of heavily-weathered or poorly preserved plant, invertebrate and vertebrate fossil. Precious opal commonly occurs in sites where fossil remains are well defined and, indeed, high grade gem quality opal is often associated with finest preservation in fossil material.

Opalised fossils are three-dimensional replicas of plant, invertebrate and vertebrate remains in which biomineral has converted to Opal-A, a hydrated form of silica -

SiO2.nH2O. Although usually described as pseudomorphs (Archer et al. 1985;

223 Flannery et al. 1995; Molnar 1999; Clemens et al. 2003), preservation modes are varied. Internal microstructure is often recorded in fine detail and at the other extreme, steinkerns of plant material and invertebrates are relatively common, and occasionally, empty molds replicate only the shapes of organic objects (pers. obs.). This patchiness may reflect a single disjunct distribution but does not preclude subsequent episodes of silicification. There has been little investigation of preservation processes, of replacement minerals, or of duration, timing or conditions required for hardening, dessication or remobilisation of mineralizing solutions during opalised fossil diagenesis (Smith 2005).

Internal microstructure is preserved in fossils when dissolution and replacement reactions are tightly linked, and finest-scale preservation requires complete continuity between the two processes, that is, no free space at the reaction front as fluids move through the decomposing object (Putnis 2002). Pewkliang et al. (2004: 268) demonstrate that microstructural detail in opalised bone is less precise than in non-opalised bone in which biomineral is recrystallised as bioapatite – ‘opalisation is not a closely coupled dissolution-reprecipitation reaction’.

The Griman Creek Formation is part of a vast system of volcanogenic andesitic sediments covering almost 2, 000,000 km2 of the Carpentaria, Eromanga and Surat Basins, deriving from an ‘Andean type magmatic arc to the north east’ (Li and Powell 2001). Perhaps partly in the form of volcanic ash, this volcanogenic material was transported up to 2000 km and deposited subaerially in a relatively unweathered state (Exon and Senior 1976). Beds of volcanic ash are particularly favourable to wood petrification due to the high solubility of volcanic glass, a rich source of dissolved silica for groundwater (Mustoe 2003; Daniels and Dayvault 2006).

Formation models for opal and opalised fossils that are based on a Tertiary timing for silica deposition or an extraneous silica source (Pecover 1996, 2005; Dowell and Mavrogenes 1999; Rey et al. 2005; Deveson 2004, 2005) fail to acknowledge that fossil diagenesis requires anaerobic burials that inhibited decomposition, in the presence of sufficient mineralizing fluid (silica) to allow dissolution of biomineral and mineral replacement to occur simultaneously.

224 Silicified plant vascular tissue occurs in the opal levels and overlying sandstones in the form of short bundles of grey fibres or tracheid tissue (e.g. LRF276). Under magnification the fibres resemble transparent glass needles, each one representing an endocast of a tracheid cell (pers. obs.). The capillary tubes are either separate and loose, disintegrating at the slightest touch, or cemented together by secondary silification. Tracheids are the long hollow cells that conduct water and mineral salts in the primary xylem of vascular plants. Capillary action continues after the plant dies and solutions in burial sediments are readily taken up. Amorphous silica in the form of Opal-A precipitates from silicic acid on cell walls (Mustoe 2003). Opal-A eventually converts to Opal-CT, a microcrystalline mixture of cristobalite and tridymite that ultimately may transform to chalcedony and then quartz. The opal to quartz transition is irreversible and under normal conditions may take tens of millions of years (Deer et al. 1980; Daniels and Dayvault 2006).

The bundles of tracheid fibres in the opal deposits do not display gem colour play and laboratory analysis confirms that they are composed of cristobalite (Henk Godthelp, pers. comm.) and are heat resistant (pers. obs.), unlike Opal-A which cracks and disintegrates at high temperature. Cristobalite or tridymite form when opal is destroyed by heating or dessication (Darragh et al. 1976), however their presence does not necessarily indicate high temperatures at diagenesis (Deer et al. 1966).

Around 100 mya, large volumes of organic material were interred at Lightning Ridge when sediments of volcanogenic origin were reworked by seasonal flood events. By this time ‘the Jurassic Andean-type magmatic arc in eastern Australia had begun to collapse’ (Li and Powell 2001: 266). Preservation of fossils and their internal microstructure requires low temperatures and stable conditions at, and following, deposition. This argues against any model that involves saturation by superheated fluids and suggests that in areas where opalised fossils occur, volcanic eruptions, geysers, hot ash flows and pyroclastic blasts were not part of the immediate palaeoenvironment. There is no indication at Lightning Ridge of postmortem or postdiagenetic disruption or re-elaboration of biofacies, as might be expected with explosive syntectonic or hydrothermal upheaval. Postdiagenetic compression and compaction of fossils is readily attributable to small-scale swelling

225 and contraction of hydroplastic clays (pers. obs.). The vertical brecciated zones so integral to the syntectonic and mound springs models are primary apposition structures, bedding disturbances and deformities common to sedimentary deposits worldwide (pers. obs.; after Pettijohn 1984).

Dowell and Mavrogenes (1999) examined the chemical composition of black opal nobbies but did not consider or investigate opalised fossil diagenesis. Their model proposing that black opal formed within the rhizosphere of plants (for example, Eucalyptus populnea Bimble Box) during the Quaternary seems incompatible with presence of black opal in fossil material of Albian age. However, isotopic evidence that black opal is biogenic corresponds with the widely held view that opal forms as a byproduct of microbial action and is consistent with Behr et al. (2000) and Behr (2001) who isolated and validly dated extinct fossil microbes in Lightning Ridge opal. The author could find no references to discovery or investigation of fossil microbes inside opalised fossils, a subject warranting future consideration.

Finch Claystone consists of 60-65% silica-rich kaolinite, up to 20% smectite (low alumina content) and 5% illite (Watkins 1984; DMR undated), with quartz and iron as dominant trace materials and a high calcite content. Smectite is extremely hydroplastic (Greensmith 1981), giving a putty-like consistency so the claystone is a near-perfect casting medium. Particle size averages 45 μm, ranging to 55 μm (DMR undated), providing exquisite replication of surface details in opalised fossils. These finer claystones are predominantly potassium-rich, detrital clays typical of coastal floodplains. Generally smectite and illite form in alkaline conditions and are favoured by warm humid climates (Deer et al. 1966; Greensmith 1981). Silica is freely released during weathering of these lithologies, probably assisted by organic acids and enzymes excreted during bacterial metabolisation.

What is a nobby? Lightning Ridge produces an endless variety of silica formations – sheets, husks, boxworks and melikaria - that are a record of cracks, gas-holes and fractures in the claystones. There are also amorphous, spheroidal or botryoidal nodules of potch or precious opal, known locally as nobbies. Contentious in origin (Hiern 1964; Byrnes 1976; Watkins 1984; Smith and Smith 1999a), nobbies are unique to Lightning

226 Ridge, suggesting diagenesis controlled by geochemical processes peculiar to the freshwater deposition.

Some nobbies may be ichnofossils. ‘Steel band’, a sandstone layer heavily indurated with silica, sometimes carries traces of invertebrate activity on the undersurface, suggesting a depositional interval or diastem. The underlying claystone represents the bed of a waterway or riverbank and the steel band, deposited over the top, marks a hydrological change. ‘Chinese hat’ nobbies, which are tabular nodules with irregular radial striae on the broader surfaces (Hiern 1964), often occur below the steel band, cone oriented downwards (pers. obs.). In these situations, certain nobbies may be casts of invertebrate burrow openings, similar to Monocraterion sp., typical of terrestrial, fresh and brackish water environments (Greensmith 1981). The Coocoran fields produce a range of problematic lanceolate specimens with a shaft that is often quadrilateral in section (Smith and Smith 1999a). These resemble glauberite crystals (pers. obs.); or cone-in-cone structures as described by Pettijohn (1984: 470: 12-8). Some are probably plant shoots, growing points or lignotubers (as per Daniels and Dayvault 2006); or the dermal ossicles of large teleost fish (Susan Turner, pers. comm.).

Microbial involvement in silica precipitation is widely acknowledged (Horton 2002; Skelton et al. 2003; Daniels and Dayvault 2006; Senior and Chadderton 2007). Nobbies resemble algal accretions (such as spheroidal or cone-shaped stromatolites) or fungal growths. There are similarities to the microbial mats of thalloid-forming Charophyceae, which develop concentric laminate structures that ‘spread horizontally across the surface of the substrate’ (Willis and McElwain 2002).

Certain nobbies appear to be pseudomorphs of hollandite nodules (pers. obs.). Hollandite, a manganate of manganese, barium and ferric iron, is an important opal indicator (Senior and Chadderton 2007) that may be bacterial in origin. Hollandite occurs commonly in the opal levels as small black botryoidal nodules.

Concretions form outward from the center by precipitation from solution around a nucleus such as a shell or bone, but unlike concretionary limestone nodules for example, nobbies do not contain fossils. Most nobbies appear to be either secretions,

227 that is, secondary structures deposited from solution within cavities, in which deposition is inwards; or accretions, that is increasing by external addition or accumulation. Like concretions, nobbies provide a record of ‘the condition of the sediment at the time of deposition [and] consolidation’ (Pettijohn 1984: 462). Shape, surface texture and inclusions are a code to hydrological and chemical conditions before, during and immediately subsequent to silica precipitation.

Lithologies that produce spheroidal or ‘chinese hat’ nobbies are usually, but not always, separate from fossil-bearing horizons. Crisply-defined fossil material occurs in association with indeterminate forms that seem to be distorted organic elements, showing a trend from sharp to blurred resolution that is a phased and consistent geochemical transition (pers. obs.). This gradation from fossil to amorphous nodule may be partly taphonomic, reflecting sequences of anoxic and aerobic conditions, and/or pH oscillations. Classic spheroidal and ‘chinese hat’ nobbies are different geochemical entities from this indeterminate material and significantly, no individual, precisely-preserved opalised fossil is part fossil, part nobby. Even so, the occurrence of nobbies in silica-saturated claystones with a high organic content infers microbial contribution to their formation, strongly suggesting that nobbies formed in geochemical tandem with fossildiagenetic processes.

What is opal? In common opal, spheres of silica of irregular size are arranged randomly. In precious opal, the silica spherulites contain concentric rings, are uniform in size and arranged evenly. Stacking irregularities create lattices that act as three-dimensional diffraction gratings. At specific angles of incidence, these scatter light into different single wavelengths or colours (Jones et al. 1964; Darragh et al. 1976). Although micro- and molecular scale mechanics under natural conditions are poorly understood, leading to much speculation on timing and influencing factors, there is general agreement that spherulite development (opalisation) was a Tertiary event. Silica spheres pack geometrically in solutions with low ion concentration and pH ranging from 7 - 10 (Smallwood et al. 2005). Initial investigation of opalised fossil diagenesis led to the startling conclusion that ‘silica spheres … [may not] gently settle from solution as they do in synthetically grown opal’ and that ‘opal [may] not initially form as a gel and then solidify’ (Pewkliang et al. 2004: 268). More recently,

228 Senior and Chadderton (2007) demonstrate gamma-ray anomalies in opal-bearing sequences and argue that silica spherulites develop around radioactive nano-nuclei that filtered downwards from the Cumborah Gravels in the presence of natural uranium and thorium.

The fossil flora and fauna

Flora (Figs. 43-45) As mentioned previously, the biomass component of the opal-bearing claystone is very high. Apart from silicified plant tracheid cells, petrified or agatised wood is also common at Lightning Ridge, where logs to 60 cms in girth are reported, often spanning the interface between Wallangulla Sandstone and Finch Claystone (pers. obs.). The largest known to date is 9.5 metres long and up to 30 cms thick. These specimens are usually comprised entirely of permineralised xylem tissue, and microstructure often resembles Wollemia nobilis Wollemi Pine, showing rays, bordered pits, latewood and early wood (pers. obs.). None of this abundant material has been studied. Huge petrified logs are also encountered at Coober Pedy in the Bulldog Shale.

At the other extreme in terms of size, Molyneux’ field and Kellie’s One (sites 31 and 32) have produced Australia’s first Early Cretaceous charophytes (Martinez- Colon 2005), represented by microscopic opalised gyrogonites. Charophytes signify non-marine and marginal marine environments - ‘Each genus, species and morphotype indicates different ecological conditions, such as ephemeral or permanent water bodies, acid to alkaline waters, littoral or deeper zones, gravel to slimy bottoms, high or low temperatures, lentic or lotic water bodies, ionic composition and principally different degrees of salinity’ (Garcia 1994: 44).

36 of the 40 microsite assemblages in the survey are dominated by weathered, weakly compressed and poorly preserved plant debris that lacks structural definition. In this miscellaneous material, internal lattice-like formations are at least partly determined by cellular anatomy and represent networks of cracks that formed by shrinkage or dessication as the organic material decomposed (pers. obs.). In the eroded plant detritus, angular cavities often contain tracheids (preserved as

229 cristobalite) showing secondary walls and bordered pits under magnification (pers. obs.).

Detrital litter may occur in association with large quantities of fresh unworn material, sometimes exquisitely preserved, as at site 12. Better-defined specimens show branchlets and stem segments with bases of leaf scales and nodes, and the debris may include cones, sporibili and sporophylls; diverse fruiting bodies and reproductive structures such as seeds, pods and drupes, including bilobial and nut- like specimens; dessicated cones; detached cone scales; and cone or catkin cores bearing mosaic patterns of small scars. Most material seems to be araucarian or cycad-like, however a great diversity of forms is indicated. Equisetes sp. (horsetails) are represented by fluted cylindrical fragments (sites 15 and 35). An unidentified plant with paper-thin leaves in wide stem-clasping sheaths is found at site 12. Unopalised compression prints in claystones from the opal levels are rare but are now known from Molyneux’, Bald Hill and Grawin. Material preserved in this manner includes twigs, reed-like scraps, fruiting structures, gingko-like and Phlebopteris-like leaf fronds (e. g. LRF271; pers. obs.).

Research on Australian Mesozoic flora has been limited largely to study of leaf impressions and pollen grains (Douglas 1994, 2000; Dettman 1994) and ‘meagre macroplant data’ is available for Aptian-Albian localities other than the Gippsland and Otway Basins in Victoria (Henderson et al. 2000: 380). Plant macrofossil from Lightning Ridge is unstudied and presents great potential for researchers. Vegetation communities probably resemble co-age floras of Queensland and Victoria, which were dominated by araucarian, sequoian and podocarp conifers with an understorey of pteridosperms, lycopods, cycadeoides, ferns and fern allies. Groundcovers were fungi, mosses, liverworts, bryophytes, lycophytes and Isoetales (Douglas 1969, 1994; White 1984, 1986; Dettman 1994; Henderson et al. 2000). The occurrence of dense and complex vegetation communities at high palaeolatitude infers forest structures determined by winter darkness and insolation, unlike anything known today (Douglas 1994). Possibly these were open forests with emergent species widely spaced (Hill 1994; Spicer 2003), and maybe larger trees developed an asymmetric pyramidal crown, with leaf surfaces directed to the north to maximize photosynthesis.

230 Investigation of this material is likely to provide data on biotic transitions concurrent with landmark events of the Australian Early Cretaceous - sea level rises in the early Aptian (Veevers 1984, 2001; Frakes et al. 1987; Quilty 1994; Cook and McKenzie 1997); warming of global climates and retreat of the inland sea from the Surat Basin in the Albian ‘leaving large areas of fringing swamps and lagoons’ (Douglas 1994: 180); and emergence of angiosperms in the Australian fossil record (Dettman 1994).

Fauna (Appendix 3.0; Figs. 42-69) Foraminifera No micropalaeontological investigation has been undertaken since 1983, when three marine forams that are characteristic of the youngest faunal assemblage from the Great Australian Basin were identified (Scheibnerova 1983). These were in core samples from 11 of 43 locations near the township, not from the microsites detailed here.

Ichnofossil (Fig. 46) Worm trails and invertebrate pathways are sometimes seen on the sole surface of steel band and sandstone horizons (pers. obs.). Polychaete worm burrows (cylindrical tubes with ‘U-bends’) occur at sites 11, 31, 32 and elsewhere. Finely stippled tubes with rounded terminations, lacking internal septa or lamina, are a common structure (Smith and Smith 1999a) - these may be opalised ‘gas vent’ pipes, scolites (fossil worm burrows), rhizoliths (after Jerzykiewicz et al. 1993) or casts of crustacean burrows similar to those of callianassid shrimps (Raup and Stanley 1971). Wood fragments from Molyneux’ field show meandering feeding trails of undetermined insects (LRF3, Fig. 46A). LRF4 preserves two empty cavities or molds of ?coleopterid larvae. Coprolites seem to be relatively common but are difficult to distinguish from nobby formations (LRF869, LRF870, LRF871; Fig. 46C, D).

Mollusca (Figs. 47, 48) 30 of 40 microsites provided pelecypod bivalves, the most common fossils apart from plant material. Beds of mussel shells are known at McNamara’s, Bill de

231 Boer’s, Potch Point, Hawks Nest and Snowy Brown’s (Smith and Smith 1999a), and mass aggregations occur at the Shallow Four Mile and many Coocoran fields (pers. obs.). Six taxa of freshwater hyriids and hyridellines are identified. Palaeohyridella godthelpi Hocknull 2000 is abundant at the Coocoran but scarce in areas near the township; Coocrania hamiltonbrucei (Kear 2006) is less common. Additional taxa not previously reported, and possibly undescribed, include - a very large ?hyriid (LRF798); a small (12 mm) equivalved ovoid sphaeriid (LRF1154-1160) with deep zig-zag ornamentation on the umbones (Fig. 47B); a large ?tellen, nuculaniid or nut- shell (Fig 47A); and a corbiculid (LRF13; Fig. 47C). The Lightning Ridge corbiculids are tiny (6 mm), subcircular, equivalved and equilateral with very fine growth lines and no ornamentation. Corbiculids are small freshwater or estuarine bivalves previously unknown from the Australian Cretaceous.

The gastropod fauna is of considerable interest and unusually diverse (Smith and Smith 1999a), with at least five families recorded (Robert Hamilton-Bruce pers. commun. 2002). Three endemic taxa () are described (Hamilton-Bruce et al. 2002, 2004; Hamilton-Bruce and Kear 2006) and the extant genus Notopala sp. is reported. Viviparids are known from Jurassic-Recent in Europe and these earliest Australian records suggest a pre-Jurassic Pangean origin for the group. The thiarid whelk Melanoides godthelpi Hamilton-Bruce et al. 2004 is rare except in particular sites on the Coocoran where mass accumulations form shell conglomerates (Fig. 48B, C). There is at least one additional thiarid taxon and further groups as yet undescribed (pers. obs.). Work now underway on camaenids and succineids (Hamilton-Bruce et al. 2006) will provide information on water quality, substrate and palaeohabitat.

Crustacea (Fig. 49) Gastroliths of freshwater crayfish are relatively common, at 27 of 40 sample sites. Fossilized ‘yabby buttons’ are absent from other Australian Mesozoic locations but are known from Tertiary sites (Henk Godthelp pers. comm.). These paired disc- shaped structures are secreted inside the stomach or proventricular of freshwater crayfish and land crabs, acting as stores of calcium salts for hardening the exoskeleton after molting (Barnes 1980). Modern Australian crayfish are members of a Pangean group, the Parastacidae (Merrick 1994). The Albian form cannot be

232 diagnosed taxonomically, however detailed morphometric analysis and comparative study might be rewarding.

Chondrichthyes (Fig. 50) About six small chondrichthyan teeth are known from the Coocoran fields and Jag Hill. Privately owned but adequately recorded in casts and photographs, these are small and gracile, with crown and root perpendicular in rostrocaudal view (Smith and Smith 1999a). They resemble teeth of the cretoxyrhinid Cretolamna appendiculata (Kemp 1991), a long-ranging cosmopolitan form (Early Cretaceous- Early Eocene) widespread in Cretaceous Australia, known from Queensland (Toolebuc, Alluru and Mackunda formations) and .

Actinopterygei/Teleostei (Figs. 51, 52) Kemp and Molnar (1980) reported two unidentified teleosts and many additional specimens are now available, representing at least four taxa (Susan Turner pers. comm.). The material is unstudied. Isolated elements of large bony fish, mainly dentary fragments and vertebrae, feature at 13 of 40 microsites. A shallow mandible bearing six teeth (Fig. 52) is associated with bone fragments with a linear striated texture and a disc-shaped vertebra. Cylindrical in section and very robust, the teeth are widely-spaced with the pulp cavity exposed at the front, and are set in a shallow trough which bears subsidiary grinding nodules (Smith and Smith 1999a). A number of dentary fragments preserve tooth bases with complex infolded margins (LRF21, site 17; LRF723, site 5; LRF177). Small teleost elements are rare but sites 31 and 32 yielded tiny teeth, cranial fragments and vertebrae, demonstrating that small fish were an important faunal component. These sites also produced several rectangular scales ornamented with heavy ridges and tubercles (Fig. 52), similar to ganoine scales of Richmondicthys sweeti Bartholomai 2004, an aspidorhynchid teleost from the marine Toolebuc Formation and Alluru Mudstone (Albian) of Queensland.

In 1996, the isolated skull of a small eel was found by opal miner Ormie Molyneux at a field known appropriately as Ormie’s Luck on the Coocoran (Smith and Smith 1999a; Fig. 51). This specimen appears to be the earliest known evidence of the family Anguilliformes (Tom Rich pers. commun.). The specimen is privately owned

233 but good casts are held at Monash Science Centre and the Australian Museum. Only four Cretaceous eels have been described, of uncertain affinities and the oldest previous record is Urenchelys from the ? of Kansas (Wiley and Stewart 1981).

Dipnoi (Fig. 53) Ten microsites yielded lungfish tooth plates and specimens are known from many other locations (pers. obs.). Lungfish postcrania rarely fossilize (Kemp 1991) so presence of branchiostegals is noteworthy (Fig. 53E). Kemp (1991) reported three taxa at Lightning Ridge, documenting: Ceratodus wollastoni Chapman 1914; an undetermined Ceratodus sp.; and Neoceratodus forsteri Krefft 1870, the extant species of southern Queensland, a true survivor (Kemp and Molnar 1981). Variation in tooth plates and jaw elements may be due to ontogeny, diet and environmental factors (Kemp 1990) and taxa are differentiated on size, width of grinding surface, length of lateral ridges and medial angle, among other features. Several Lightning Ridge specimens exhibit dental caries as described by Kemp (2003). Tooth plates of C. wollastoni suggest individuals to more than 1.5 metres, and the second Ceratodus sp. was even larger (Kemp and Molnar 1981; Kemp 1991) – a specimen from site 17 (LRF222) measures 60 x 45 mm. N. forsteri is more common than C. wollastoni and juvenile material for both taxa is present.

Anura Site 32 yielded a tiny fragment of maxilla, now under study at the University of New South Wales (Henk Godthelp pers. comm.). This is an important record: the previous oldest Australian frog is from the Eocene Tingamarra Fauna of southeast Queensland (Mike Tyler and Henk Godthelp pers. comms.) and the Lightning Ridge material extends the record in south-eastern Gondwana by over 50 million years. The only other amphibians known from Cretaceous Australia are temnospondyls from the Victorian Gippsland Basin (Henderson et al. 2000).

Testudines (Figs. 2-28, 37-38, 54) Turtle remains survive taphonomic and post-excavation processes better than many other vertebrate elements, comprising up to 75% of the vertebrate material in 28 (or

234 approx 60%) of the 40 microsite assemblages. Most turtle elements at Lightning Ridge represent small to medium individuals, but many locations produce tiny elements apparently of hatchlings, juveniles or sub-adults.

Turtle bones are particularly common on the Coocoran fields (Smith and Smith 1999a). In this context, absence of turtles at relatively well-sampled sites that produce vertebrate material is noteworthy. No explanation is currently available for lack of turtles from several of the Three Mile locations. The aberration may be taphonomic or might reflect habitat preference.

The Lightning Ridge turtle fauna includes land-living meiolanoids, at least two chelid pleurodires and at least two indeterminate taxa. Remains of the meiolaniid- like forms Opalania and Spoochelys were found together only at site 35, which produced evidence of several individuals of various sizes. Spoochelys and Sunflashemys apparently coincide in the same biofacies at site 24, however inadequate sampling and large quantites of indeterminate material suggest that these taxa may overlap taphonomically and stratigraphically more often than presently indicated. Interestingly though, Sunflashemys and Spoochelys were separated stratigraphically at site 34, where evidence of Spoochelys was found in the older level at 26 m and the Sunflashemys type was at 13 m.

The two indeterminate taxa are indicated by single elements (Fig. 54A, B), as follows: 1. AMF128018 is an isolated first peripheral with a fine rasp-like surface texture, chelid-like polygonal pattern and vascular microstructure that resembles Spoochelys, Sunflashemys and Opalania. There are significant differences however. In AMF128018, the cervical scute is very large, geometrically angular and quadrilateral, broader at the rear, with straight margins. A triangular marginal adjoins the cervical, between the cervical and an uninflated and poorly defined supramarginal. The visceral surface is horizontal, unlike the condition in Spoochelys and Opalania.

235 2. An indeterminate carapace fragment at the Australian Museum, Sydney (Fig. 54, B) has an adocid-like surface ornamentation of prominent, widely-spaced linear tubercles and nodules. This highly distinctive decoration is unlike that of the other turtle morphotypes in the Lightning Ridge assemblage.

Ichthyosauria (Fig. 55) An unusual vertebral centrum (LRF724; site 5) is hesitantly identified as ichthyosaurian. The specimen is notochordal, broken transversely and subcircular in rostral view. The material is unstudied but may be significant for palaeoecological reconstruction, as these are marine reptiles.

Sauropterygia (Fig. 56) Plesiosaur teeth are relatively common, present at 17 of 40 survey sites and many other locations (Smith and Smith 1999a, 1999b). These specimens are 5-50 mm in size, subtriangular in section near the apex, with fine longitudinal striae, smooth on the buccal surface. Most are shed specimens and many exhibit wear features, abrasion surfaces or breakages that occurred in life (Kear 2006; and pers. obs.). Subtle morphological differences - in curvature, taper, basal width and constriction, enamel texture and root form - may be ontogenic, or taxonomic, or related to position in the tooth row, or weathering (Massare 1987; 1997).

Plesiosaurs are known from non-marine locations overseas (Sato et al. 2005) and near-shore and freshwater locations in Australia (Bartholomai 1965; Cruikshank and Long 1997; Vickers-Rich 1996). At Lightning Ridge, plesiosaur teeth are associated with plant debris, viviparids, crayfish gastroliths, lungfish toothplates and dinosaur elements, evincing a form that was well adapted to freshwater conditions. The Lightning Ridge teeth may be referrable to Leptocleidus sp. however more skeletal elements are needed for diagnosis (Kear 2006).

The scarcity of sauropterygian postcrania as noted by Smith and Smith (1999a) has not been remedied. A ?pliosaur limb bone from Lightning Ridge was mentioned by Ralph Molnar (1980). AMF102462, the notorious ‘Million Dollar Bone’ from

236 Foster’s claim on the Sheepyard field was suggested as a pliosaur humerus (Long 1998) although this is disputed (Kear 2006).

Lepidosauria - Squamata A tiny fragment with two teeth in place appears to be the oldest known snake dentary (John Scanlon and Henk Godthelp, pers. comm.; site 32), although this identification is tenuous. The material is under study at the University of New South Wales.

Crocodylia (Fig. 57) Lightning Ridge is the only Australian Mesozoic locality yielding more than one crocodylian: Crocodylus (Botosaurus) selaslophensis Etheridge 1917; a ziphodont crocodile; and a third morphotype with circular tooth sockets (Molnar and Willis 2001; pers. obs.). The former two are small animals, however the size of tooth base fragments (LRF226, for example) suggests that the round-tooth form was large. Tiny crocodile teeth are relatively common on the Coocoran fields (sites 11, 25, 31 and 32), evidence of juveniles and breeding activity. Again, there are several morphotypes, variously constricted at the gum line, smooth, finely striated or fluted, some with faint anterior and posterior carinae.

C. selaslophensis (AMF15818, AMF15819) is represented by a partial maxilla with six short smooth conical teeth, curving inwards and faintly constricted at the base, set in an alveolar groove. The material is unusual and identification tenuous (Molnar 1980). Cervical, sacral and caudal vertebrae and podials were catalogued with the holotype with some hesitation, but uniformity of potch colour and texture certainly suggests that the material derives from one location (pers. obs.). There are now many examples of the procoelous crocodile vertebrae that were described and reviewed by Molnar (1980). A number of semi-procoelous dorsal vertebrae in which the neural arch is a broad laminate shield with zygapophyses set level resemble the atoposaurid neosuchian Theriosuchus (Mesoeucrocodylia) from Spain (Brinkman 1992) and Asia (Wu et al. 1996).

237 The ziphodont crocodile has a broad snout and flattened skull and is represented by two maxillary (AMF103588 and AMF103589) and two dentary fragments (AMF103587). Alveoli are slightly elongated and anterior dentary teeth procumbent, an unusual feature in Mesozoic archosaurs. Too incomplete for phylogenetic analysis, this taxon may belong to the clade formed by Gobiosuchus and Mesoeucrocodylia (Molnar and Willis 2001).

The third taxon is represented by two maxillary fragments (Fig. 57D, E), a large form with deeply sculpted cranial bones, festooned jaws, robust conical teeth showing size variation along the tooth row, and an overbite (pers. obs.).

A partial articulated crocodile skull consisting of the parietal, squamosal, pterygoid and supraoccipital is held at the Australian Museum, Sydney (Fig. 57A, B). This exceptional specimen, preserved in transparent potch showing internal details of nutrient and nerve sulci, would provide an excellent brain endocast (Smith and Smith 1999b). The pitted ornamentation corresponds with isolated dermal plates from Kellie’s One (sites 31 and 32; LRF521) and resembles that of Isisfordia duncani Salisbury Molnar Frey and Willis 2006 from Winton, Queensland. Isisfordia is the most primitive eusuchian. The Lightning Ridge crocodyliforms are slightly older and have also been identified as basal eusuchians (Molnar and Willis 2001; Salisbury et al. 2006). Study of the Lightning Ridge material may permit review of Mesozoic crocodylians in Australasia, provide data on neurological development in the group (Paul Willis pers. comm.) and help to establish a Gondwanan origin for modern crocodiles.

Pterosauria (Fig. 58) Fine hollow bone fragments are tentatively assigned to (Phil Currie pers. comm. via Henk Godthelp), and two isolated, straight slender teeth (site 25; and LRF769, site 5), resemble those of Ornithocheirus sp. from Morocco (Wellnhofer and Buffetaut 1999.

Dinosauria (Figs. 59 – 64)

238 Dinosaur bones are few and far between in Australia (Molnar 1997) and dinosaur records lag far behind those of other continents (Weishampel et al. 2004). The crucial significance of Australian occurrences is underpinned by the fact that by 1990, information on dinosaurs was ‘based on only about 2000 articulated skeletal fragments’ worldwide (Dodson 1990, cited by Russell 1993).

Understanding of dinosaur evolution in the far-flung eastern sector of Gondwana is enhanced by recent discoveries in Antarctica (Hammer and Hickerson 1994; Molnar et al. 1996; Gasparini et al. 1996), Queensland (Molnar 1996a and 1996b; Steve Salisbury and Scott Hocknull pers. comms.), Victoria (Rich 1996; Vickers-Rich 1996; Rich et al. 1997; Rich and Vickers-Rich 2001, 2003), New Zealand (Molnar and Wiffen 1994; Wiffen 1996) and the Chatham Islands (Stilwell et al. 2006).

Lightning Ridge is the only location in New South Wales that consistently yields dinosaur material. Dinosaur remains are known from Sheepyard, Grawin and Carters Rush in the west, throughout the Coocoran and township fields, and north to Mehi and Angledool in southern Queensland (Smith and Smith 1999a). 30 of 40 survey assemblages include dinosaur elements, and collection deficiency probably accounts for their absence from several other microsites. Investigations of Mesozoic continental dinosaur assemblages centre on Late Cretaceous localities in North America (Pereda-Suberbiola et al. 2000), and while the total number of published dinosaur related studies increases exponentially, only a small percentage are devoted to dinosaur taphonomy (Fiorillo and Eberth 2004). The rich palaeofauna and mosaic of depositional environments at Lightning Ridge suggest great potential for dinosaur research.

Hypsilophodontids are relatively common at Lightning Ridge, their presence shown at 16 of the survey sites and many other locations (pers. obs.; Smith 1997). When hypsilophodontids were first documented in Australia (Molnar and Galton 1986), Fulgurotherium was known from only a few broken thigh bones from Lightning Ridge. A number of new femora reveal a large size range, and minor variations are of taxonomic utility (Tom Rich pers. commun.), indicating that the hypsilophodontids are as diverse as in Victorian sites, where four or five genera and at least five or six species are present (Rich at al. 1988; Rich and Vickers-Rich

239 2001). Postcranial material includes axials (cervical, dorsal, sacral and caudal vertebrae), appendicular elements and podials. An articulated crus and proximal tarsus, and an articulated femur, tibia and astragalus with exceptional surface detail (site 9) are held at the Australian Museum, Sydney. Other important material includes a very large tibia distal fragment (LRF1289, site 40); and semi-articulated and associated axial and podial elements from site 24 (LRF968, LRF970, LRF972, LRF974, LRF979, LRF980, LRF981, LRF983, LRF984, LRF987 and LRF991).

Cranial material for hypsilophodontids is rare. sp. is represented by a small tooth (Fig. 59B; site 25; Smith and Smith 1999a) and a dentary fragment with germ tooth (LRF766, site 5; Smith 2008). Two tiny dentary scraps, with germ teeth that are significantly different in each specimen, suggest two pigeon-sized taxa (Fig. 59A). In , dentaries of juveniles are relatively deeper than those of adults (Carpenter 1994) and the shallow gracile mandible of these Lightning Ridge specimens indicates adult animals, separating them from Victorian taxa, in which the dentary is robust. Midget dinosaurs are a peculiar aspect of Australian near-polar locations and the diminutive hypsilophodontids of Lightning Ridge and Victoria are among the smallest of dinosaurs.

A muttaburrasaur, smaller and perhaps more primitive than M. langdoni (Molnar 1996, 1997) is indicated by two tooth specimens (QMF14420, QMF14421; site 2) with high crowns and parallel vertical ridges (Smith 1997). Evidence of large ornithopods includes a scapula from Nebea 6 Mile (at the Australian Museum, Sydney) and postcranial material from Fosters’ claim (Sheepyard field), a site described as ‘one of the richest assemblages of dinosaur bones found anywhere in Australia’ (Ritchie 1989).

At Thorleys Six Mile, a huge hand and foot print bulge from the sandstone roof of an underground tunnel. These are attributed to a large -like ornithopod and the manus print is reminiscent of from North America (Molnar 1991; Smith and Smith 1999a). The marks were impressed into the surface of a mudflat or river bank that was strewn with organic debris (site 7).

240 A possible stegosaur is scantily represented by a dermal scute with median crest and distinctive ropey internal structure (Ben Kear pers. comm.; pers. obs.; specimen at the Australian Museum, Sydney).

Two large partial vertebrae and a pelvic element from Smith’s Field at the Coocoran, and at least one isolated tooth (LRF660) may represent a prosauropod (pers. obs.; Fig. 60). Anterior articulation facets of the vertebrae are platycoelous, circular and very broad compared to the short central bodies which are laterally compressed. There are similarities to posterior dorsals and anterior caudals of Plateosaurus and Cetiosaurus (Bonaparte 1986). The tooth has a squat, spatulate crown and lacks serrations. Wear surfaces are apparently developed by tooth-to- tooth abrasion as in Yunnanosaurus (Galton 1986), producing a sharp chiseled cutting edge with enamel borders ‘form[ing] a slightly raised rim around the dentine’ (Galton 1992: 327). Prosauropods are a Late Triassic-Early Jurassic Pangean group, found on all major continents (Wilson and Sereno 1998; Galton and Upchurch 2004) including Antarctica. The Australian prosauropod Agrosaurus macgillivray Seeley 1891 (Nomina dubia, according to Galton 1992), is apparently based on a mislabeled tibia of the English prosauropod Thecodontosaurus (Vickers- Rich et al. 1996; Galton and Upchurch 2004). A prosauropod record in the Albian of Australia would considerably extend temporal and spatial distribution for the group.

Sauropods are absent from contemporaneous Victorian sites (Rich et al. 2002) although present in Queensland (Molnar 1991; Upchurch et al. 2004). At Lightning Ridge, sauropods are represented by hefty vertebral centra, unfortunately not in public ownership, and by up to 20 peg-like teeth, some exhibiting wear facets (Fig.61). The more robust morphotypes are similar to the basal titanosauriform from Early Cretaceous Japan (as per Barrett et al. 2002: 1200, 1201: 1-16). Slender, pointed specimens, subcircular in section with minimal curvature resemble teeth from Brazil that are also attributed to a titanosaurid (Kellner 1996: 620, 621: 7). In addition, a trackway in the ceiling of a mine at the Nine Mile resembles sauropod swimming tracks as known from Morocco (Ishigaki 1989). The pathway consists of a series of crescent-shaped ?manus prints marking the passage of at least two individuals (Ben Kear pers. comm.; pers. obs.).

241 Lightning Ridge produces the best-preserved and most abundant theropod fossils in Australia. Theropod elements occur at nearly half the survey sites and many other locations (pers. obs.). To date, only two taxa are formally described, both on single elements held by the British Museum, London. Walgettosuchus is known from a caudal vertebra that ‘could belong to any of three theropod families … including the Allosauridae’ (Molnar 1991); and Rapator is based on a presumed first metacarpal similar to that of Allosaurus (Ralph Molnar pers. comm.). Rapator is currently classed Tetanurae incertae sedis (Weishampel et al. 2004). If BMNHR3718 is a metacarpal, the posteromedial process (buttress) ventrally overlaps metacarpal II, indicating affinities with Coelophysis, Allosaurus, segnosaurids, ornithomimids or dromaeosaurs (Russell and Dong 1993). This is unhelpful diagnostically and a new interpretation offers fresh opportunities for analysis. John Long (In Press?) and other workers (Holtz: November 2001) suggest that BMNHR3718 is the manual phalanx 1 of digit 1 of an alvarezsaurid resembling Mononykus and Shuvuuia from Mongolia, and Patagonykus from Argentina (Novas 1996). If so, Rapator is not a theropod but a large flightless bird, the giant of this very enigmatic group, and among the earliest.

Theropod elements indicate a broad range in size and taxonomic diversity. Important articulated and semi-associated specimens (axials and podials) were found at sites 15, 24, 25 and 28. At least two teeth at the Australian Museum, Sydney, apparently represent a small spinosaurid (Ben Kear pers. comm.; and pers. obs.). Ornithomimosaurids are represented by a vertebra (LRF543) from site 32 (Henk Godthelp pers. comm.) and excellent vertebral material from the Three Mile (e.g. LRF409; Fig. 64). Small, extremely gracile and attenuated elements evoke a diversity of bird-like theropods that were probably plumed or feathered (for example LRF353, one of an articulated group; Fig 64).

Small theropod teeth that have been identified as ‘dromaeosaurid-like’ by Phil Currie (Henk Godthelp pers. comm.) are known from Victoria (Currie et al. 1996), very rarely from Queensland and from Lightning Ridge, including six of the survey sites (Smith and Smith 1999a, 1999b; Smith 2008; Fig. 63; LRF34; LRF35; LRF36; LRF660; LRF319; LRF312). Theropod tooth morphology is of taxonomic utility and North American specimens are copiously documented (Currie 1987; Currie et

242 al. 1990; Farlow et al. 1991; Fiorillo and Currie 1994; Fiorillo and Gangloff 2000; Sankey et al. 2002). All the same, given the degree of convergence in theropod tooth structure, identification of the Lightning Ridge teeth remains uncertain – for example, tooth morphology in a possible coelurosaur from Uruguay (Perea et al. 2003) is strikingly similar to the Lightning Ridge specimens. The Lightning Ridge teeth exhibit typical dromaeosaurid-like variation along the tooth row, strong recurve, hourglass-shaped basal section, serrations confined to posterior carina and an anterior carina that twists onto the lingual surface. Extreme lateral compression (FABL often twice the lateral width or more), markedly flattened buccal surface and sub-serration structure separates the opalised specimens from overseas forms. One example with root preserved (LRFR456) was found in association with a large ungual or clawbone, laterally compressed, deeply curved and sickle-shaped (LRFR455) implying a formidable predator.

The largest opalised theropod bones yet recovered in Australia have been found at Carter’s Rush, about 65 km west of the Lightning Ridge township (Fig. 62). Unstudied hindlimb elements represent a theropod that was at least three metres high at the hip (LRF100 - LRF105). This articulated and associated group includes a metatarsal III, 320 mm in length, comparatively more elongated than that of Allosaurus. Articulation surfaces of the shaft are flattened and metatarsi were not co-ossified but the flat contact surfaces are very extensive. Although the condition is not arctometatarsalian, metatarsal III was partly concealed in anterior view by metarsals II and IV. The broad proximal expansion resembles the primitive condition in Late Triassic and Early Jurassic abelisauroid-like forms such as Coelophysis, Syntarsus and Ceratosaurus (Holtz 1994; Tykoski and Rowe 2004).

Aves (Fig. 65) Two bird taxa from Lightning Ridge are represented by four scraps from site 13 at the Coocoran (Molnar 1999; Smith and Smith 1999a, 1999b), discovered by the author in 1992. This first evidence of Mesozoic birds from New South Wales was found in association with araucarian twigs, tiny pine cones, crayfish gastroliths and turtle elements. AMF102787 and AMF102786 are left and right tibiotarsi distal fragments of a non-enantiornithine bird from a group unknown elsewhere. AMF103590 is an avian tibiotarsus proximal section that may or may not represent

243 the same taxon. AMF103591, an avian vertebral centrum, apparently indicates a second taxon (Molnar 1999).

Several very small Hesperornis-like teeth were recovered from site 32 (Henk Godthelp pers. comm.). LRF443, from Chinaman’s Gully at the Sheepyard Field, is another contender, an extraordinary transparent specimen with exception surface detail. A central ‘pedestal’ producing a double ring of bone at the base of the tooth distinguishes these from the teeth of crocodilians and avialian dinosaurs in which the base is indented. The material is under study.

Early Cretaceous birds are scarce and Australian Cretaceous records are the earliest for Gondwana (Chiappe 1996). An enantiornithine bird Nanantius eos Kurochkin and Molnar 1997, is known from the Albian Toolebuc of Hamilton, Queensland but Victorian records are enigmatic – five feathers from Koonwarra (Aptian) and the furcula of a possible enantiornithine, from Inverloch (Rich and Vickers-Rich 2001; Walter Boles pers. comm.). These occurrences are important globally, indicating that by the middle Albian, birds were diverse, well established in southeastern Gondwana and inhabited near-polar latitudes.

Mammalia (Figs. 66 – 69) Australian Mesozoic mammals are known from Cape Otway and Inverloch in Victoria; from two locations in Queensland – the Toolebuc Formation, Hazel Creek (Godthelp 2005) and Winton Formation, Hughenden (Salisbury 2005); and from Lightning Ridge, New South Wales.

The Victorian sites yield the ausktribosphenids nyktos Rich et al. 1999 and whitmorei Rich Flannery Trusler Kool Klaveren and Vickers-Rich 2001 (Rich et al. 2001b). The oldest known (Ornithorhynchidae), Teinolophos trusleri Rich et al. 1999 from Inverloch is represented by tiny lower jaw fragments (Rich et al. 1999; Rich et al. 2001a; Rowe et al. 2008) and Kryoryctes cadburyi Pridmore et al. 2005 from Dinosaur Cove, a monotreme of uncertain status, is based on an isolated humerus. A controversial group, monotremes are more likely related to mammal-like forms of the Early Mesozoic than to later tribosphenic therian mammals, and hypothesized sister-groups include docodonts,

244 triconodonts, morganucodontids, multituberculates and ausktribosphenids, to name a few (McKenna and Bell 1997; Luo et al. 2002; Musser 2005). Monotreme records from Australia and South America (Pascual et al. 1992a, 1992b) indicate broad diversifications across Pangea and ghost lineages extending back into the Triassic (Woodburne et al. 2003).

Lightning Ridge has produced an unprecedented diversity of monotremes. The holotype of Steropodon galmani Archer et al. 1985 (AMF66763), a lower jaw fragment with three teeth, was found in old mullock or topdirt on Angledool field near the Lightning Ridge township (Smith and Smith 1999a). A posterior dentary fragment recovered by the author from Tank Five (Coocoran) is referrable to Steropodon. This specimen at the Australian Museum, Sydney, retains fragments of bone or cartilage within the mandibular foramen (pers. obs.).

Soon after discovery of Steropodon in 1985, a second mammal specimen from Lightning Ridge was reported (Rich et al. 1987). An isolated element in the Galman Collection AMF66786, was described as ‘an edentulous maxillary fragment’ from ‘an unnamed [mammal] taxon … of unclear affinities’. This identification is erroneous. AMF66786 is a turtle peripheral bone with sockets for costal rib and plastral buttress (pers. obs.).

The holotype dentary AMF96602 of Kollikodon ritchiei Flannery et al. 1995 (Fig. 66A) was discovered by opal miner Robert Sutherland, associated with viviparid and thiarid gastropods (perhaps the primary food source of this bunodont mammal), plant macrofossil and remains of lungfish, turtles (Sunflashemys), plesiosaurs and hypsilophodontid and theropod dinosaurs (Smith and Smith 1999a; sites 28 and 29; Fig. 66B). The extraordinary maxilla of Kollikodon (AMF119740) was purchased in 1999 by opal dealer and fossil collector Andrew Cody. Rather amazingly, this specimen too was found in old mullock near the township (Potch Point), as was the Steropodon dentary. Musser (2005) argues that Kollikodon is not monotreme but a basal ‘allotherian’ mammal with affinities to haramiyids and multituberculates. Kollikodon is conspicuously absent from the recent analysis (Rowe et al. 2008) of the Early Cretaceous Victorian ornithorhynchid Teinolophos.

245 At least three additional monotreme taxa at Lightning Ridge are represented by edentulous dentaries. Taxon 4 (AMF97263) is distinctively gracile and shallow, notable for the horizontal ventral rim of the ramus. Taxon 5 (site 37; specimen at the Australian Museum, Sydney) is a small dentary fragment representing a rat-sized monotreme, distinguished on dentary contour ventral to the molar row and ascending process (pers. obs.); this specimen was found by the author in a tailing heap at Olga’s Dam on the Coocoran (Smith and Smith 1999b).

Taxon 3 (Fig. 67; site 18; specimen at the Australian Museum, Sydney) was found by Clytie Smith in 2002 at Tank Five, a processing dam on the Coocoran. The Tank Five monotreme is represented by an edentulous dentary, exquisitely preserved in transparent potch but broken into four sections by mining machinery. This specimen provides more information on lower jaw morphology in Mesozoic monotremes than any other to date. The specimen is more generalized and robust than lower jaws of the modern platypus, and at over 80 mm reconstructed, indicates an about the same length as insignis Woodburne and Tedford 1975 from Riversleigh but much bulkier in body form. The jaw has alveoli for a ?canine, up to five double-rooted premolars and three molars, shows abrupt transition between molars and premolars, and a strongly-reduced last molar. Pronounced exaenodonty of the molar tooth row is indicated and an internal coronoid process and shallow meckelian groove appear to be present. The mandibular foramen contains claystone matrix and retains separate ossifications or cartilage. Ventral portions of the molar alveoli are angled lingually, reaching below and separated from the mandibular canal. This canal is hugely inflated along the entire ramus and is infilled with ?cristobalite. Premolars and a possible canine were somewhat procumbent as a result of torsion and lateral flaring of the anterior section, so that the symphyseal contact is elongated (Rowe et al. 2008). This long narrow horizontal symphysis, lateral torsion, exaenodonty of posterior molars and hypertrophied mandibular canal are typical platypus features, indicating that taxon 3 is probably an ornithorhynchid.

There are intriguing differences however. In ornithorhynchids the mandibular canal opens into a very large medial mandibular foramen ventral to the posterior limit of the toothbed. Unless the foramen is small, the mandibular canal in the Tank Five monotreme does not open laterally in the ‘masseteric’ position. The hypothesized

246 sister-group relationship between monotremes and ausktribosphenids (Luo et al. 2001, 2002; Keilan-Jaworowska et al. 2004) is strenuously contested (Rich et al. 2002; Woodburne et al. 2003), but taxon 3 exhibits clear resemblances to the Victorian ausktribosphenids (pers. obs.). Further detailed comparison is required to determine whether the following similarities are plesiomorphic: prominent mental foramen at the front of the dentary (preserved in Bishops); dental formula that includes at least five premolars and three molars; premolars and molars double- rooted; paired molar roots unequal in size; gradation in size between rear premolars and molars; P5 larger than M3; P5 submolariform (inferred only in the Tank Five specimen); P5 broader mediolaterally than M3; P5 cantilevered lingually (inferred in taxon 3); transverse alignment of partition between M1 and P5; pronounced anteromedial-posterolateral (diagonal) alignment of alveolar partitions between molars; molars with strong lingual cantilever overhanging dentary; labial walls of molar alveoli lower than lingual walls; small size of M3; anterior section of M3 anteroposteriorly compressed and trapezoidal; and coronoid facet and angular process of dentary located posteriorly and level with base of the molar tooth roots. Differences between the Tank Five specimen and the ausktribosphenids in structure of the rear section of the ramus and articular area may be partly due to poor preservation of the Victorian material. The mandibular canal is uninflated in Ausktribosphenos and Bishops, unlike the condition in the Tank Five monotreme, but it is noted that the mandibular canal is small in tachyglossids.

Monotreme postcrania is appearing on the opal fields (Fig. 68) - now consisting of four isolated vertebrae, a ?humerus and a possible tibia. LRF775 (site 5; Fig. 68C) and LRF1239 are thoracic vertebrae agreeing closely with those of Ornithorhynchus and Tachyglossus; the hypapophysis and paired foramina in the neural canal resemble Ornithorhynchus. There are small nubbin-like transverse processes set slightly above the neurocentral junction, an interesting contrast to extant taxa, in which transverse processes are absent from thoracic vertebrae and ribs lack the tubercles of therian mammals (Murray 1984; Musser 2005). Two sacral vertebrae (Fig. 68A, B; LRFR453, site 25; and LRFR454) display stout transverse processes set low, level with the ventral surface of the centrum which has a median ridge (Smith and Smith 1999a). A mode of locomotion and posture distinct from Ornithorhynchus and Tachyglossus is indicated by the form and angle of the ilial

247 facets (pers. obs.). The possible monotreme humerus (Fig. 68D; site 32), resembles that of Kryoryctes but is about 50% smaller. The proximal articulation of the tibia (Fig. 68E, F; site 36) is massively expanded, displaying deep paired fossae in the proximal surface as in Ornithorhynchus, large and complex articulation facets for the fibula, and a shaft that is strongly bowed. These important specimens are under study.

A mammal specimen (Fig. 69) was found recently at site 12. This small, gracile tibia proximal section is not a monotreme and is under study at the Australian Opal Centre, Lightning Ridge.

Finally, a mammal-like tooth (Smith and Smith 1999a; AMF118621, site 1) was described as a possible synapsid with affinities to dryolestids (Clemens et al. 2003). This specimen has two cusps linked by a crest, and a smaller cusplet. The root appears to be single and the crown overhangs it. The tooth is very large - if a mammal, this is the largest known from the Mesozoic. Examination under X-ray or CT scan would provide another line of investigation because the pulp cavity is well- preserved and filled with ?cristobalite, as are tooth hollows in the holotype lower jaw of Kollikodon. Comparison with internal morphology of other groups (where known) might be worthwhile.

Taphonomy, biases and depositions Taphonomic studies generally concentrate on Tertiary and Quaternary mammal locations in Europe (Pereda-Suberbiola 2000) and few have been undertaken on dinosaur assemblages (Fiorillo 1997; Fiorillo and Eberth 2004). Similarly, sparse Australian studies centre on Tertiary deposits (Baird 1991; Myers et al. 1998; Arena 1997) with limited work on taphonomy of Mesozoic locations (Waldman 1971; Drinnan and Chambers 1986; Vickers-Rich 1996).

Vertebrate microsites are accumulations of small well-sorted remains of multiple taxa, providing many clues for palaeoecological reconstruction (Jamnisczky et al. 2003). Ideally, all areas of the locality are equally accessible for testing and exhaustively sampled, using uniform and controlled collection techniques. This methodology is inapplicable at Lightning Ridge where collections are from artificial

248 ‘deposits’ on the surface, or from fossil horizons that are extracted piecemeal or in small sections, either horizontally or from below. Under these circumstances, the first casualty is taphonomic data. When biofacies are scrambled by opal miners, vital information is lost on areal extent of bone accumulations, spatial densities, layerings and patterns, along with data on carcass posture, skeletal layout, bone alignment and orientation (after Pereda-Suberbiola et al. 2000; Fiorillo and Eberth 2004).

The second casualties are delicate fossil specimens and . The mechanical tumbling action of opal mining machinery mimics the taphonomic effect of sorting by size and shape (pers. obs.). Hence previous reports, based on observations of opal miners’ collections, describe assortments of small, blocky, isolated elements with larger vertebrates represented by their smallest components (Molnar and Galton 1986; Archer et al. 1985; Smith and Smith 1999a). In fact, delicate, intricately-shaped specimens, semi-articulated or associated elements and microfossil material occurs in around 28 of the 40 assemblages covered by this survey. Sites with large volumes of silica in the form of nobbies and indeterminate plant material are more likely to produce larger fossil bones, and very large bone elements are known (e.g. Nebea, Sheepyard, Carter’s Rush; pers. obs.). This suggests a high proportion of low-energy burials and a geochemical rather than taphonomic tendency against preservation of large elements (pers. obs.).

Opal miners’ collections favour taxa with sturdy skeletons of mid-range body size (2-30 kg body weight), and do not accurately reflect faunal abundance and overall species composition. Excavated under more controlled conditions that included the micro-fraction, sites 31 and 32 contributed a diversity of small vertebrates, cranial elements and fragile bones with projections, spines and laminae – precisely the type of material that is destroyed during opal mining. This clearly demonstrates that the apparent scarcity of micro-vertebrates at Lightning Ridge is a collection bias. Micro- vertebrates, including mammals, are usually fairly abundant in Mesozoic assemblages and Victorian Early Cretaceous sites have supplied around 50 mammal dentaries, many of which are minute (Tom Rich and Lesley Kool pers. comms.; Rich and Vickers-Rich 2004).

249 It takes special circumstances to generate a bone accumulation and in fluvial and deltaic settings, organic material accrues as channel lag, point bar or vertically aggrading channel floor deposits (Koster et al. 1987; Jamniczky et al. 2003). At Lightning Ridge, the wide weathering range at many sites suggests attritional accumulations, and as is typical of bone assemblages preserved in flood channels, erosion due to pre-burial transportation is more common than postburial fracture or compression (pers. obs. after Behrensmeyer 1988 and Pereda-Suberbiola et al. 2000). However a high proportion of sites yield plant, invertebrate and vertebrate material that is fresh and unweathered (pers. obs.).

Previous workers with on-field experience describe a complexity of depositions - ‘lacustrine or brackish water’ (Offenburg 1967); ‘marshlands’ (Byrnes 1977); ‘a very low energy environment, possibly stagnant water’ and ‘marginal marine’ (Watkins 1984: 15). This survey confirms the freshwater setting, reinforced by evidence of charophytes (Adriana Garcia pers. comm.), occurrence in potch and opal formations of Early Cretaceous microbes typical of shallow nutrient-rich freshwater environments (Behr et al. 2000; Behr 2001); and by the invertebrate and vertebrate record.

Microsite assemblages detailed in this survey are generally dominated by plant litter arranged in random mats or parallel alignments, reflecting both high and low energy regimes. Evidence of fluviatile conditions is shown by upright or diagonal ‘dip’ in certain incomplete plant specimens that straddled a facies interval or diagenetic boundary. A white opaque mineral forms an unfinished edge signifying a sudden alteration in chemical composition of successive sediment (e. g. site 33; pers. obs.).

Most assemblages include freshwater aquatic and terrestrial invertebrates and vertebrates. Different preservation modes in molluscs (empty cavities, steinkerns and full preservation of shell structures) suggest pronounced fluctuations in pH levels, consistent with seasonal flood events (pers. obs.). The steinkerns signal acid conditions in bottom sediments, preservation of shell valves implies alkaline regimes. In places, opalised plant and bone material occur in close proximity (pers. obs.), an unusual feature of the Lightning Ridge locality, because chemical

250 conditions for preservation of plants are generally not conducive to bone preservation.

Mass accumulations of freshwater hyriids may indicate fluviatile conditions (Hocknull 2000; Kear 2006). Circular corrosion pits in the shell valves are common, typical of infaunal species living in shallow water; and networks of deep cracks and fissures in closed specimens and in those with open valves, suggest exhumation and periods of re-exposure before reburial (pers. obs.). Multiform gastropods denote a broad range of hydraulic regimes. Viviparids have limited biological tolerances and habitat preferences. Pulmonates such as limnaeids thrive in algal blooms precipitated by high nutrient loads following flooding, extant forms preferring stagnant non-flowing water, and succineids are terrestrial land snails (Hamilton- Bruce and Kear 2002; Hamilton-Bruce et al. 2002).

Fish bones do not survive post-depositional exhumation and reburial (Wiegelt 1989), hence their scarcity at sites 4, 7, 10, 13, 25, 33 and 34, where the microfossil component was partially searched may be taphonomic, suggesting bone accumulations reworked by high energy flood waters. At sites 31 and 32, small teleost elements and the unusual absence of molluscs indicate an overflow assemblage or perhaps strandline flotsam left by receding flood waters.

Palaeoecology Volumes of plant macrofossil, ichnofossil, invertebrate and vertebrate material, and rich burial accumulations in diverse depositions present much scope for palaeoecological study. At this stage, it is unclear if disparities between assemblages are stratigraphic, and because of serious deficiencies and inconsistencies in sampling methodology, conclusions on relative abundances are tentative (after Grayson 1984; Vermeij and Herbert 2004).

Aside from taphonomic variations inferring a mosaic of depositional settings, similarities in groups of assemblages from particular areas, and discrepancies in faunal mix between grouped sites from widely separated locations may carry genuine signals. Sites at Emu’s and Dead Bird, for example, yield Paleohyridella, turtles, crocodiles and plesiosaurs, with hypsilophodontid and theropod dinosaurs

251 comprising a high percentage of elements. These diverse bone beds may be primary accumulations in major waterways (pers. obs.). Sites 28 and 29 provide quantities of plant macrofossil, turtles, hypsilophodontids, small theropods and Kollikodon, and accumulations of gastropods (viviparids and thiarids) suggestive of flood channels, marshlands and billabongs.

There are interesting contrasts between the Coocoran assemblages and those of the Three Mile. Scarcity of turtles at the Three Mile sites has been discussed already and the ‘winged’ hyriids Palaeohyridella and Coocrania are absent at the same sites (pers. obs.). The sharply tapered anterior margins of these bivalves suggest rapid burrowers and mobile sediments or fast-flowing water. The implication that the primary Coocoran waterways were generally more turbulent, higher energy systems than those of the Three Mile is reinforced by sedimentary evidence. Anecdotal reports from opal miners indicate that transitions between Finch Claystone and Wallangulla Sandstone are often imprecise on the Coocoran fields, unlike the distinct bedding planes on the Three Mile; this is corroborated by examination of strata underground, and exposed in cross section in various open cut mines (pers. obs.).

The large size of crayfish, teleosts and dipnoans implies deep permanent water bodies and while scarce chondrichthyan elements indicate a near-shore environment, it is noted that sharks frequently travel upstream into inland waterways. The Leptocleidid-like plesiosaur was well adapted to riverine conditions. Aptian plesiosaurs of Coober Pedy, Andamooka and White Cliffs may have been metabolically attuned to low average water temperatures (Kear 2006; Kear et al. 2006a; Kear et al. 2006b), possibly frequenting southern regions mainly during summer. Perhaps they entered calm enclosed waters for breeding. Small plesiosaur teeth in the Lightning Ridge assemblage certainly indicate the presence of hatchlings and juveniles. Rare but intriguing evidence of Richmondichthyes, anguilliformes and ichthyosaurs at Lightning Ridge suggests that pelagic, marine and migratory forms invaded freshwater systems on the coastal margins, possibly on a seasonal basis. Ichthyosaurs may have been more opportunistic in feeding behaviour than previously thought (Kear et al. 2003). Crayfish ecdysis, and breeding and hatching of lungfish, turtles, plesiosaurs and crocodiles probably occurred

252 simultaneously during brief warmer months, providing a bountiful seasonal food source for predatory groups. At this time, larger aquatic and terrestrial vertebrates that were capable of seasonal migration may have moved in from northern localities.

The overall high proportion of theropod elements (Figs. 62-64) is interesting becauser herbivores greatly outnumber carnivores in any given ecosystem (Farlow 1997). It is unclear if a similar anomaly exists in Victorian dinosaur assemblages. The number of dromaeosaurid-like teeth (nine specimens from survey sites, approx. 40 specimens cited in total; pers. obs.) implies an animal scavenging or hunting in the waterways (Smith and Smith 1999a). Although usually found with hypsilophodontid remains, the theropod teeth also occur with monotreme elements (sites 18, 28). This theropod had a straight pointed muzzle with teeth oriented perpendicularly along the margins of the jaw bones, too delicate to cope with large prey. The animal was not biting into hard shell or bone, as teeth were shed with sharp apices, inferring a ‘cut and slice’ action rather than crushing function. Other features are noteworthy: when these specimens are transparent, internal microstructure is visible, revealing that slits between serrations are connected to transverse microtubules (Fig. 63B). This may be a specialization for grappling in water with slippery prey but it also suggests the likelihood of a bacterially-toxic bite (Smith and Smith 1999a; Abler 1992). Presumably an infectious bite would be most effective against animals with an elevated metabolic rate such as monotremes and perhaps hypsilophodontids.

The ‘law of the lower jaw’ dictates that this element, ‘bulky but light in weight [lacking] an extensive basal attachment’ detaches first, is transported separately and not readily eroded, although teeth are lost’ (Wiegelt 1989: 84, 85). Six monotreme dentaries and about the same number of crocodylian lower jaws have been found, suggesting that the monotremes were aquatic. Their remains turn up in sites near the township as well as the Coocoran, implying use of a range of riverine and wetland habitats (pers. obs.). Comparable cranial material for hypsilophodontids is scarce – only six teeth from survey sites and approximately nine specimens cited in total for the entire locality (pers. obs.), and four lower jaw fragments (only three of which are in public collections). This may indicate that hypsilophodontids favoured upstream habitats distant from swampy or deltaic areas.

253 Bone features such as size, shape, types, fractures, weathering, surface and predator marks provide substantial ecological data (Behrensmeyer 1978). Dessication cracks are rarely seen in the bone elements, but a dentary fragment assignable to Steropodon (pers. obs.; specimen found by the author at Tank Five, Coocoran, now at the Australian Museum, Sydney) exhibits fissuring possibly caused by prolonged aerial exposure prior to burial (pers. obs.). Molnar (1980) noted incision trails of an invertebrate borer on a plesiosaur podial. Clemens et al. (2003; and Ralph Molnar pers. comm.) observed that circular pitting on the large synapsid-like tooth (AMF118621) might be due to stomach acids following ingestion. Specimens from site 9 are extraordinarily ‘fresh’ and unweathered with skin or cartilage scraps preserved, but the hypsilophodontid tibia and turtle humerus exhibit deep stepped fractures and compression splintering suggestive of predation by scavengers, and the tibia shows a series of regular parallel scratches that match the serrations of the dromaeosaurid-like theropod teeth (pers. obs.). A hyriid mollusc (LRF800) displays paired indentations and associated depression fracturing consistent with vertebrate tooth marks (Kear and Godthelp 2008).

Palaeoclimate In the Early Cretaceous, New South Wales was closer to the south magnetic pole than at present - 65o-70oS (Henderson et al. 2000; Veevers 2001; Li and Powell 2002). During the Aptian, geological indicators such as cryoturbinates, glendonites, glacial erratics and ice-rafted dropstones indicate highly seasonal, cool to very cold temperatures possibly with winter freezing in more southern Australian locations (Frakes and Francis 1988; Rich et al. 1988; Dettman et al. 1992; Vickers-Rich 1996; Kear 2006; Kear et al. 2006). However global greenhouse conditions prevailed throughout the Cretaceous and ice sheets may not have developed during the warmer interludes (Li et al. 2001; but see Stoll and Schrag 1996, and Borneman and

Norris 2008). This global warmth may have been a consequence of elevated CO2 levels caused by ‘extraordinary global magmatism’ at ‘six large igneous provinces’ during the Cretaceous (Tarduno et al. 1998). Evidence is compelling for mild climates worldwide during the Albian, with surface temperatures possibly 6o-12oC warmer than present and sea temperatures of 17oC (Dettman et al. 1992; Henderson et al. 2000). Even at palaeolatitudes of 70o-80oS, biotic records for Victoria and New

254 Zealand imply equitable conditions, determinations that are soundly reinforced by the Lightning Ridge record.

Palaeofloral studies supply crucial information on past climates (Wolfe 1981; Upchurch and Wolfe 1988; Spicer 2003), providing evidence of cold conditions, fluctuations in water supply and marked seasonal variation in Early Cretaceous southern Australia (Parrish et al. 1991; Hill 1994; Quilty 1994; Dettman 1994; McLoughlin et al. 2002). In the Victorian assemblages, this is inferred from pronounced growth rings in petrified logs, indications of deciduous vegetation, and small leaf size, among other measures (Vickers-Rich 1996). Similar growth rings in petrified timber, and layered mats of plant detritus occur at Lightning Ridge. Importantly though, ‘no protocol currently exists to reliably quantify palaeoclimatic parameters from analyses of pre-angiosperm leaf morphologies’ (McGloughlin et al. 2002). A predominance of small sclerophyllous leaves may be partly a taphonomic artifact, because broad soft leaves are less likely to preserve. Actually, a high percentage of plant fragments at Lightning Ridge bear remnants of wide stem- clasping ribbon-like leaves, suggestive of mild conditions (pers. obs.).

Faunal evidence for a relatively warm palaeoclimate is presented by forms whose descendents are now restricted to temperate or subtropical regions, though distributions and tolerances in extant members may be misleading (Rich and Vickers-Rich 1989; Spicer 2003). Thermal tolerances for extinct groups are calculated on biological requirements in groups that phylogenetically bracket them (Tarduno et al. 1998) and presumably most invertebrate and vertebrate taxa in the Lightning Ridge assemblages were at the thermal limit of their distribution range.

Today Australian viviparids are confined to tropical and temperate inland northern and central regions, south to the Murray River (Allen 1950) and their presence during the Albian implies warm conditions. It is unclear at this stage whether the absence of bivalve molluscs, viviparids and freshwater crayfish from co-age Victorian sites is attributable to chemical conditions adverse to preservation of calcium carbonate structures, or to more extreme climatic conditions at these slightly higher latitudes.

255 Latitudes 40o restrict the distribution of modern freshwater crayfish. Functional morphology and behaviour patterns of this conservative group are probably unchanged over millions of years (Merrick 1994 citing Hasiotis 1992). Growth is regulated by water temperature, slowing down or ceasing entirely in winter (Merrick 1994; Smith et al. 1998; Borsboom 1998). Molting and breeding follow fixed seasonal cycles, occurring synchronously during growth periods in warmer months, the timing determined by day length (Barnes 1980?). Before molting, crayfish gastroliths are shallow, plate-like and roughly textured. At Lightning Ridge, the preponderance of fully-formed hemispherical gastroliths implies burials that occurred in wamer seasons, during high rainfall and flooding events. Gastroliths to 28 mm diameter represent large individuals that molted infrequently and survived many seasons.

Now restricted to the tropics despite their previous range into both northern and southern polar regions (Rich and Vickers-Rich 1989), extant lungfish cannot breed in water colder than 10oC (Vickers-Rich and Rich 1993), and given the conservatism of the genotype, mild conditions during the Albian are indicated by their presence at Lightning Ridge and Victoria.

Distribution of extant non-marine turtles is climatically limited (Paul 1988) and occurrence of turtles in the Late Cretaceous high Arctic at ~ 80oN is reported as indicating ‘extreme climatic warmth’ (Tarduno et al. 1998). Length and warmth of summers affects survival of eggs and hatchlings of modern turtles, and a warm- month average temperature of at least 25oC and more than 100 frost-free days per year are essential for breeding. Non-marine turtles were breeding at Lightning Ridge during the Albian, and their biological requirements strongly suggest a relatively benign palaeoclimate. Modern chelids cannot tolerate temperatures below ~10oC (Lapparent de Broin and Molnar 2001) and their distribution is climatically restricted. Today large land turtles of similar bauplan to the meiolanoids mostly inhabit hot dry savannah regions. Marine protostegids are abundant in Early Cretaceous Queensland but are not recorded to date from other Early Cretaceous Australian localities. Their absence from the marine opal fields of South Australia may be due to colder climatic conditions and deeper marine offshore deposition (Kear 2003). Protostegid material may eventually appear at Lightning Ridge,

256 perhaps from an area such as Jag Hill, where the fossil assemblage suggests greater marine influence than in the more southern opal fields of the Lightning Ridge locality.

Freshwater bivalves, crayfish, lungfish, and turtles survive cold and dessication by aestivating in deep mud. Extreme cold is inimical to large aquatic reptiles and today crocodiles tolerate only mild freezing (Paul 1988; Upchurch and Wolfe 1988). The three Lightning Ridge crocodilians, and tiny shed crocodile teeth indicating juveniles, again signify a warm palaeoclimate, but quite possibly burrowing or hibernation behaviour of some sort assisted these ectotherms during extreme seasons.

Burrowing behaviour is also typical of monotremes and a ‘rotation-thrust’ fossorial capability is postulated in Kryoryctes from Dinosaur Cove (Pridmore et al. 2005). Monotremes may have been particularly well-adapted to icy winters and polar darkness. Gross expansion of the mandibular canal in Steropodon, the ornithorhynchid from Tank Five and Teinolophos imply that the rhinarium was equipped with electrosensory receptors, as in the modern platypus, a facility that would be equally advantageous in winter darkness and in turbid or fast-flowing water. This capacity, endothermy, fossorial habits and hibernation may have been crucial to the success and diversification of monotremes in near-polar environments.

Today near-polar faunas are generally larger than those of temperate and tropical latitudes, and certainly Steropodon, the Tank Five monotreme and especially the ?synapsid from Lightning Ridge (Clemens et al. 2003) would outweigh some of the crocodilians and dinosaurs in the assemblage. Nonetheless the suggestion that large body size in the monotremes is an adaptation to icy conditions (Flannery et al. 1995, reiterated by Musser 2005) fails to account for diminutive monotremes (Teinolophos and taxon 5), tiny ausktribosphenids and pygmy dinosaurs. Plainly, this unique co- existence of pint-sized dinosaurs with monotremes and a ?synapsid that were Mesozoic mammalian giants requires further investigation.

Bone histology studies indicate that Victorian hypsilophodontids did not hibernate and probably remained active during polar winters (Chinsamy et al. 1998). In fact,

257 endothermy may have been fundamental to survival and diversification of these small ornithopods in southeastern Gondwana (Vickers-Rich and Rich 1993; Chinsamy et al. 1998).

At palaeolatitudes of 65o, polar twilights are long for most of the year and at 75o, there are several weeks or months of total darkness (Spicer 2003). Large size of eyes and optic lobe in the hypsilophodontid are adaptations to low light conditions (Vickers-Rich 1996); a similar explanation is given for large eye size in troodontids of Cretaceous Alaska, where these small theropods were unusually diverse (Fiorillo and Gangloff 2000). The protostegid Bouliachelys from Hughenden (pers. obs.) and the terrestrial turtle Spoochelys from Lightning Ridge both have large eye orbits. Large orbits in the marine form could be an adaptation to turbid or deep water but this would not apply to a terrestrial turtle, suggesting that this is another specialised response to winter darkness.

Prosauropod and theropod remains from Beardmore Glacier, Antarctica (ca. 65o- 70oS; Early Jurassic) are cited as evidence for a mild palaeoclimate (Hammer and Hickerson 1994), observations equally applicable to Lightning Ridge during the Albian. Uncommon in near-polar locations (Rich and Vickers-Rich 2002), sauropods are normally associated with tropical and drier temperate palaeoclimates, and terrestrial dry-land habitats with a sharp dry season (Bakker 1986; Paul 1988; Henderson et al. 2000). Possibly they were seasonal visitors only at Lightning Ridge.

Several groups that endured the polar winters survived increasing aridity and extreme heat as Australia drifted north in the Late Cretaceous and Tertiary. Extant taxa include velesunionine bivalves and viviparids such as Notopala sp.; freshwater crayfish; and the lungfish Neoceratodus forsteri. Meiolanoids, the turtles with the longest evolutionary history and Ornithorhynchidae, the oldest known mammal family, occupied the region for at least 150 million years. Chelid pleurodires probably had a Jurassic history in Australia and are still thriving. Perhaps the Mesozoic near-polar location pre-adapted these ancient and conservative groups to extreme weather conditions. Persistent forms still rely on the ability to aestivate or hibernate in deep mud or underground burrows as a protection against starvation,

258 dessication and thermal extremes. Behavioural tactics that served in freezing cold now serve in heat and drought. Fascinatingly, these behaviours assisted the same groups through the Late Cretaceous event (Jeffrey Stilwell pers. comm.).

Biogeography Documentation of Early Cretaceous faunas in South Australia, Victoria, New South Wales and Queensland is preliminary but sufficient to justify comparisons across several deposition basins (Eromanga, Surat, Gippsland and Otway) within the eastern section of Gondwana. Palaeontological data from Lightning Ridge significantly augments information on the bioregion, at a time of evolutionary innovation and anomalous palaeoclimatic conditions. Certainly however, when records are based on calcium carbonate structures as for molluscs and crayfish, which do not preserve in certain palaeoenvironments, and on single bone elements, as for numerous taxa, faunal distributions may be artifactual, not actual. Apparent variations could be due to habitat preferences and biological limitations, or geographic barriers, or simply the result of poor sampling.

Of all the Australian opal fields, only the Winton and Griman Creek Formations are non-marine in origin, and opalised remains of freshwater and terrestrial vertebrates are otherwise scarce. The marine deposits of South Australia yield crinoids, bivalve and gastropod molluscs, belemnites, ichthyosaurs and sauropterygians (Kear 2003; Kear et al. 2006; and pers. obs.), with evidence of cold to very cold palaeoclimatic conditions (Kear 2006). A near-shore environment is indicated, however one or two lungfish toothplates and dinosaur elements (Kear 2006) have been found at Coober Pedy, and large petrified logs are encountered in the opal-bearing sediments. Dinosaur elements have also been recovered from Andamooka, consisting of type material for Kakuru kujani Molnar and Pledge 1980 (a tibia distal section and referred phalanx, both specimens now missing); a small vertebral centrum of an unidentified theropod; and hypsilophodontid material (Kear 2006). White Cliffs in New South Wales has produced sauropterygians and a possible ichthyosaur (Kear 2005), as well as lungfish toothplates (Kemp 1991) and hypsilophodontid elements (Ben Kear pers. comm.). From the ‘boulder opal’ fields of south-western Queensland comes rare evidence of freshwater and terrestrial forms. Opalised material from Winton and Yowah includes wood, araucarian seed capsules

259 (LRF1345), tree fern sections (LRF212), scolites representing annelid or polychaete worms (LRF44), possible sauropod bone (pers. obs.) and a single theropod tooth resembling the dromaeosaurid-like specimens from Lightning Ridge and Victoria (pers. obs.).

Groups apparently exclusive to New South Wales and Queensland include hyriidelline bivalves, Richmondichthyes sp., sauropods and Muttaburrasaurus sp. On present evidence, the Lightning Ridge vertebrate fauna agrees more closely with the Victorian assemblages. Although muttaburrasaurs, prosauropods and sauropods are absent from Victoria, Fulgurotherium, Atlascopcosaurus and other hypsilophodontids, ornithomimosaurs and monotremes are known only from the more southern localities. Recent discoveries however extend the range of hypsilophodontids and dromaeosaurid-like theropods into the Cenomanian of Queensland, not only reinforcing their status as the most common dinosaurs of Early Cretaceous Australia, but indicating that additional similarities to the southern assemblages are likely to appear with further exploration of Queensland localities.

Many groups appear to be endemic to Lightning Ridge – this includes most of the molluscs (Coocrania, Albianopalin sp., Melanoides and numerous undescribed taxa), the three turtles Spoochelys, Sunflashemys and Opalania, Botosaurus and the ziphodontid crocodilian, the prosauropod, Rapator, the possible synapsid, and Steropodon, Kollikodon and other monotremes.

Origins of the Australian Cretaceous terrestrial fauna are speculative. Vicariant events cannot be resolved when systematic frameworks are weak, and the earliest record for a taxon is unreliable as an indication of origin (Russell 1993). Single and fragmentary bone elements ‘do not a summer make’ and require special deference. Nevertheless, information increases exponentially with every new fossil record in the southern hemisphere and south polar locations.

During the Aptian Albian, south-eastern Australia was a peninsula of Gondwana, hemmed in by geographic barriers – the epicontinental Eromanga Sea and the Tethys Sea to the north and west, the magmatic arc of the Pacific margin on the north-east (the ‘Whitsunday Volcanic Province’; Veevers 2001) and Antarctica to

260 the south. Even so, faunal exchange between southern supercontinental landmasses would have been possible during periods of high global temperatures such as the Albian. Early Cretaceous Australian faunas then may have consisted of ancient Pangean relics and more recent immigrants from other sectors of Gondwana. Faunal groups in Early Cretaceous Australia were subject to extreme geographic isolation and extreme climatic conditions. The high proportion of relic and endemic taxa (Henderson et al. 2000) accords with the view that by acting as safe havens maintaining relic species, possibly due to lower predation intensity, and by supporting groups that progressively adapt to special conditions, polar locations become centres of evolutionary innovation (Vermeij 1987; Vickers-Rich 1996; Rich 1996).

Relics include lungfish (Kemp 1991), a (Thulborn and Turner 2003), temnospondyl amphibians that were extinct elsewhere by the Late Jurassic (Vickers- Rich and Rich 1993), meiolanoid turtles (this volume) and rhomaleosaurid plesiosaurs that may be Triassic-Early Jurassic in origin (Kear et al. 2006). A single astragalus suggests persistence of allosaurids after their Jurassic demise elsewhere. Prosauropod elements from Antarctica (Hammer and Hickerson 1994; Rich et al. 2002) imply that an occurrence at Lightning Ridge, extending the stratigraphic history of this group from Late Triassic to Early Cretaceous, is feasible palaeogeographically. Monotremes are presumed to have originated no later than middle Jurassic (Musser 2005) and probably much earlier (Woodburne et al. 2003) and their presence in South America and unrivalled diversification in Early Cretaceous Australia are evidence of ancient Pangean populations. The vast majority of formally named taxa and undescribed morphotypes in terrestrial and freshwater aquatic faunas from Early Cretaceous Australia appear to be endemics, at least at a generic level, consistent with controls on faunal interchange, in the form of biogeographic barriers, filters and corridors (Henderson et al. 2000). It is assumed that geographic isolation increased after the Albian when Australia progressively rifted from Antarctica (Vickers-Rich 1996; Li and Powell 2001).

Araucarians, cycadioides, Nothofagous, ceratodontid lungfish, meiolaniids, chelid and pelomedusoid pleurodires, protostegids, numerous dinosaur taxa (hadrosaurids, ceratosaurids, spinosaurids and abelisaurids) and monotremes are cited on

261 comparatively sound evidence as Gondwanan in origin (Archer et al. 1985; Russell 1993; Flannery et al. 1995; Hirayama 1998; Henderson et al. 2003; Kear and Lee 2005). In addition, Early Cretaceous Australian assemblages include many early, and earliest, records that might imply evolutionary novelties moving outwards from the eastern sector of Gondwana. In this category are viviparid gastropods, anguilliformes, and meiolanoid turtles. Victorian records for protoceratopsian, ornithomimosaurid, oviraptorosaurid and dromaeosaurid dinosaurs, and ausktribosphenid mammals have prompted claims of affinity with Asian faunas (Rich and Vickers-Rich 2001), even the suggestion that during the Mesozoic, terrestrial vertebrates ‘island-hopped’ across the Tethys Sea, from south to north, between eastern Gondwana and Eurasia (ibid.). Once again, some of the data is rudimentary and several of the identifications from New South Wales and Victoria are based on one or two isolated bone elements. Moreover a simpler explanation is emerging. As the fossil record gradually improves, tends to drop out of the picture as the source and destination of faunal movement to and from eastern Australia, and evidence increases of Pangean or Gondwanan interchange.

Take for a start, the diverse and cosmopolitan hypsilophodontids, known from mid- Jurassic to Maastrichtian (170-65 my) in Europe, North and South America, Asia, Antarctica and New Zealand, as well as Australia. The common ancestor of ‘non- iguanodontid euornithopods’ including the heterodontosaurids (considered ancestral to hypsilophodontids), probably originated in Asia before the mid-Jurassic (Sues 1997; Norman et al. 2004). The unparalleled diversity of hypsilophodontids in eastern Gondwana suggests development from a basal lineage that dispersed into South Africa early in the mid-Jurassic, well before the Aptian-Albian by which time northern and southern hemispheres had attained their separate biogeographic identities (Russell 1993). Therefore, a mid-Jurassic Gondwanan origin for the Australian groups may be more plausible than a later incursion from Asia. In northern hemisphere assemblages, hypsilophodontids are rare components that may have been higher altitude or ‘upland’ forms and thus pre-adapted to polar conditions (Vickers-Rich 1996). The fact that despite their wide spatial and temporal distribution across Europe and Laurasia, only one northern hemisphere polar record is known (late Campanian-early Maastrichtian, Colville River, Alaska) might

262 indicate that polar regions were ‘off limits’ to more derived members and that it was the generalised ancestral forms that were favoured at higher palaeolatitudes.

Theropods had an extremely long history in the Australian region (Thulborn 1998) and a southern hemisphere origin for the Australian dromaeosaurids is also possible. Dromaeosaurids range from Early Cretaceous China to late Maastrichtian North America, but a Jurassic origin as suggested by Currie (1997) is confirmed by recent discoveries in Late Cretaceous Madagascar. This new material suggests that dromaeosaurids may be a Gondwanan group that colonized Madagascar well before its separation from Africa during the Early Cretaceous. The records do not represent late immigration events but lineages that survived on the island long after their isolation from the mainland (Fanti and Therrien 2007). Presence of dromaeosaurids throughout Pangea before the break-up of the supercontinent during the Late Jurassic suggests that the Australian taxa are more credibly Gondwanan in origin than Asian.

Sauropods are first recorded in the Early Jurassic but their sister taxon Prosauropoda is already present in the Late Triassic. The oldest neosauropod material is Late Jurassic, implying that the neosauropod radiation commenced before the breakup of Pangea. Titanosaurids were the dominant herbivores in South America throughout the Cretaceous, and their southern distribution suggests a Gondwanan origin. ‘Aberrant’ titanosaurid-like taxa in the northern hemisphere may be relics of the more primitive neosauropod radiation (Wilson and Sereno 1998; Henderson et al. 2000). So far, near-polar sauropods in the southern hemisphere are known only from Australia and New Zealand (Wiffen 1996; Molnar 1997; Rich et al. 2002).

Ornithomimosaurs are no longer safely assumed as ‘Cretaceous coelurosaurian dinosaurs from Eurasia and North America’ because new material from Late Jurassic Africa, although tenuous, may extend the record into Gondwana (Osmolska 1997); and ankylosaurs, once considered a northern hemisphere group, are now known from Argentina, Antarctica and New Zealand, as well as Victoria and Queensland (Molnar 1980, 1997; Wiffen 1996; Vickaryous et al. 2004).

263 In regard to the Australian non-marine reptiles, it appears that Early Cretaceous terrestrial and freshwater turtles (meiolanoids and chelids) are principally Pangean or Gondwanan forms. The discovery in Queensland (Winton Formation) of the eusuchian crocodile Isisfordia, augmented by recent phylogenetic and biogeographic analysis of crocodyliformes, implies a Gondwanan rather than Laurasian origin for modern crocodiles, including those of Lightning Ridge (Salisbury et al. 2006). Freshwater plesiosaurs, on the other hand, are thoroughly cosmopolitan, known worldwide from early mid-Jurassic to Maastrichtian (Kear 2006).

Thus although some uncertainty exists for some taxa, a Pangean origin is likely for the majority of vertebrates in Australian Early Cretaceous terrestrial assemblages. Prominent among those of unclear antecedents are the Victorian oviraptorosaur and neoceratopsian, and ausktribosphenid mammals. ‘Unquestionable’ evidence of oviraptorosaurs is known only from Asia and North America and relationships are unresolved (Barsbold 1997; Osmolska et al. 2004). Neoceratopsians occur from the Late Jurassic-Maastrichtian of Asia and North America, with isolated and meagre records in South America and Australia (Rich and Vickers-Rich 2003) that are considered by some workers as ‘dubious on biogeographic grounds’ (Dodson 1997). The ausktribosphenids are controversial systematically and phylogenetically (Luo et al. 2001; Keilan-Jaworowska et al. 2004) and the group is currently known only from Early Cretaceous Australia.

Significantly, data increasingly points to faunal exchange across the southern supercontinent in the Early rather than Late Mesozoic. Although new records of abelisauroid predators from Cretaceous Africa imply active interchange between the western sections of Gondwana until the end of the Early Cretaceous (Sereno et al. 2004), restrictions on faunal movement to and from south-eastern Gondwana, and particularly between east and west Gondwana, may have been established well before the Aptian-Albian (Molnar 1997; Lapparent de Broin and Molnar 2001).

The ‘central question in historical biogeography is the influence of continental fragmentation on the evolution of terrestrial vertebrate faunas’ (Wilson and Sereno 1998). New fossil material from Mesozoic southern hemisphere locations will

264 progressively assist in palaeogeographic reconstructions. Meantime it is apparent that where phylogenetic affinities of Australian Mesozoic taxa are discernible, these are predominantly with ancient southern hemisphere forms. While ‘no major groups of local origin are apparent’ (Henderson et al. 2000), prevalence of odd and anachronistic taxa in south-eastern Gondwana implies isolation in the Early Cretaceous sufficient to promote development of numerous endemic lineages.

In summary, the Finch Clay Facies at Lightning Ridge (middle Albian) represents a continental lowlands deposition. Palaeochannels correlate with centers of silica precipitation and sediments extracted by opal miners (mullock, tailing heaps and silt tank residues) are a vital palaeontological resource. Articulated and associated vertebrate elements and microvertebrate material is recovered when lithologies are searched methodically and the microfraction is included. An accurate picture of taxonomic diversity and faunal composition over this huge locality is yet to emerge.

Fossil assemblages comprise plant debris, freshwater aquatic invertebrates and vertebrates, and/or terrestrial vertebrates from floodplain habitats, and sparse elements of marine groups. There are bivalve and gastropod molluscs; crayfish; chondrichthyans; actinopterygians and dipnoans; anurans; turtles; sauroptyergians; a squamate; three crocodylians; and pterosaurs. Dinosaurs include prosauropods, titanosauriformes, hypsilophodontids, muttaburrasaurids, and ornithomimosaurid and dromaeosaurid theropods; and at least two ornithoracine birds. Mammals include monotremes and other groups.

Temperate and subtropical biota indicates a mild palaeoclimate despite the high palaeolatitude, but cool to cold winters, and months or weeks of polar twilight imply a palaeoenvironment without modern equivalent. Endothermy, enhanced optical acuity and electrosensory capabilities in turtles, hypsilophodontids and monotremes may be adaptations to environmental extremes. Polar winters would promote burrowing, aestivation, hibernation, nomadism and migration. Summer breeding of crayfish, lungfish, turtles, plesiosaurs and crocodylians would provide seasonal feeding for larger aquatic vertebrates including ‘invaders’ from marine habitats, and terrestrial predators.

265 The fauna is characterized by local and regional endemism, indicative of geographic isolation; early records for several groups; relic species reminiscent of Triassic and Jurassic populations; and faunal links with southern Pangea and western Gondwana, not with Laurasia.

266

CHAPTER ELEVEN

PALAEOECOLOGY OF TERRESTRIAL AND FRESHWATER TURTLES OF LIGHTNING RIDGE, NEW SOUTH WALES

In previous chapters of this thesis, three new turtles from Lightning Ridge, New South Wales, were described and analysed, and evidence was presented of up to four additional groups, including chelid pleurodires. Understanding of the palaeoecology of these turtles is hindered by poor stratigraphic and taphonomic information, incomplete type material and rudimentary data on localized distribution; the subject is very much ‘a work in progress’. Nonetheless, structural evidence provides some guidance on the biology of the turtles, and aspects of behaviour and lifestyle can be deduced from associated biota and palaeogeography.

Spoochelys ormondea, Sunflashemys bartondracketti and Opalania baagiiwayamba were heavily-built terrestrial turtles, and the chelids were freshwater aquatic forms. At Lightning Ridge turtle bones occur in assemblages of weathered plant detritus, with invertebrates that are typical of floodplain, marshland and riverine habitats, and a broad range of mostly freshwater and terrestrial vertebrates. Considering the abundant evidence for large, mobile water bodies (for example, mass aggregations of hyriid and palaeohyriid mussels), there is little doubt that remains of fully aquatic, fluviatile turtles, and quite possibly sparser elements of marine turtles, are represented albeit unrecognized among the multiple fragments in various collections.

Spoochelys material is more common than material of Sunflashemys (see microsite survey results - Appendix 2.0.2), yet Sunflashemys was the more water-adapted form. Sunflashemys has slightly more gracile limb elements, elongated and narrowed bridge peripherals with weakly upturned gutters, and flared posterior peripherals creating the hydrodynamic carapace shelf that is a typical aquatic specialisation (Brinkman 2005). The occurrence of Sunflashemys elements in areas of the Coocoran where

294 viviparid snails and thiarid whelks are common (Chapter Ten; sites 28, 29) may signal that ponds or swamp forest were the preferred habitat. Spoochelys remains are more widespread, occurring in a range of depositional conditions, in varied assemblages. The significance of these differences cannot be gauged without further field investigation.

A terrestrial origin for turtles is argued on grounds of forelimb morphometrics in stem turtles (Joyce and Gauthier 2004; Joyce 2007). Complete articulated forelimbs are not preserved for the Lightning Ridge taxa and measurements are estimates, however the short ‘stumpy’ manus and pes, and digit count of 2222? firmly places Spoochelys and Sunflashemys with Proganochelys, Palaeochersis and Meiolania, in mid-range of the ‘terrestrial field’ as defined by Joyce and Gauthier (2004). The very high olecranon process, bonding of lower limb bones, and overlapping metacarpals and metatarsals are further ‘land-living’ signals. Bulbous plantar expansions of the astragalocalcaneum in Spoochelys and in unstudied material that may be assignable to Opalania are typical of plantigrade land turtles (Gaffney 1990); and Opalania had sturdy hoof-like unguals similar to Meiolania.

As predominantly terrestrial forms, these taxa were vulnerable to predation by large carnivores such as theropods, and presence of crocodylians and plesiosaurs meant that aquatic environments were equally hazardous. Protective structures and defensive behaviours would have been as vital as adaptations to the extreme near-polar climate. During early turtle evolution, protection of the vulnerable head and neck was a crucial priority, achieved in several ways - by cranial and cervical ossifications (Proganochelys and Meiolania); by nuchal outgrowths projecting as ‘horns’ or splints from the carapace (in nanhsiungchelyids; Hirayama et al. 2001); by lateral and vertical neck retraction (in casichelydians); and projection of the carapace over posterior cervicals (Palaeochersis and Proterochersis). The carapace extension that is so pronounced in Early Cretaceous Australian meiolanoids suggests that primitively, lateral neck retraction was a defensive rather than predatory mechanism. Apart from the biconvex fifth vertebra, a suite of synchronized, chelid-like cervical specialisations is evident in these groups. Perhaps development of the biconvex fifth

295 cervical articulation marked the advent of the predatory ‘ambush strike’ feeding mode in pleurodirans.

The skull of Spoochelys was high, fully roofed and possibly spiney and in adult animals, the dermal scutes may have thickened into bosses and projections. The large orbital fossae may signify an adaptation to low light conditions at near-polar palaeolatitudes, and/or in cryptic undergrowth habitats. Most of the short neck, which retracted laterally, was protected below the anterior carapace shelf, which was strengthened by a series of thick elliptical bony domes. The tail was very wide and long and the peculiar sloping condition of central articulations and large transverse processes indicate great strength and mobility in the anterior section, and a propensity for powerful or sudden tail swinging. Progressive enlargement of haemal keels suggests that a distal club or ossifications of some sort were developed. While these caudal features might imply a scudding function when swimming, the skull and shell specializations would be of limited use in an aquatic turtle.

‘Inframarginal musk glands’ in the axillary and inguinal bridge area are typical of extant Australian chelids, and scent gland secretions of Chelodina longicollis are notoriously pungent and effective in deterring predators (Cann 1998). Musk chambers or ‘Rathke’s gland’ cavities are described in Kayentachelys, Platychelys and some extant cryptodires (Weldon and Gaffney 1998). Sunflashemys had musk duct openings as in chelids, and the posterior bridge peripherals contained inflated hollows, the large size of which suggest that this turtle was a real stinker. Tenuous evidence indicates a subsidiary or secondary function for these cavities. In adult individuals of Proganochelys, rear peripherals contained hollows that opened through fossae on the visceral carapace surface (Gaffney 1990: 127, 124-125: 76, 77). Meiolaniid bones are characterized by a peculiar spongiform microstructure (pers. obs.; Scheyer 2007), and in Meiolania, rib ends terminate in cavities, some of which open laterally from the bridge peripherals (e. g. AMF49141 and others; Gaffney 1983: 16), a peculiar condition also seen in peripherals attributed to Spoochelys (pers. obs.). In fish, pterosaurs, sauropods, theropods and birds, development of highly vascularised or pneumatic bone microstructure and pleurocoels are specializations for

296 lightening of the skeleton. Perhaps peripheral cavities in primitive terrestrial turtles served a similar purpose, and incidentally, increased buoyancy in water.

The comparative rarity of Opalania specimens at Lightning Ridge suggests that the material is allochthonous, and that Opalania was not living in or near the waterways. Large land turtles are ill-suited to wet forest communities, extant forms mostly inhabiting hot dry savannah regions (White 1997). The bauplan of Opalania implies high thermal inertia and that in this near-polar location, long hours of basking in sunlight were critical to maintenance of core body temperature. The extreme thinness of bones in the mid-section of the carapace in Opalania, a condition that persisted in Meiolania, may be correlated with this biological requirement. Given the armoured skull in sister-taxon Spoochelys, the similarities to Tertiary meiolaniids in cranial and podial osteology, and the fact that Opalania co-existed with large predators such as theropods, Opalania probably had horns or heavy cranial scutes, and a tail club or caudal ossifications, although no direct evidence as such has been found to date.

It is not known if the pterygoid ‘teeth’ of Proganochelys and Kayentachelys indicate a durophagous diet, but a diet of soft plant material or small invertebrates in australochelyids and meiolanoids is suggested by the smooth palate and the distinctively narrow maxilla below the orbit. No doubt, vegetation communities included soft-leafed undergrowth and aquatic macrophytes that produced a multitude of fruiting structures, cones and seeds for herbivores. The palate is extraordinarily flimsy and weak in Meiolania and it has been suggested that development of accessory triturating ridges in this taxon and Ninjemys implies a specialized diet (White 1997). The sharper triturating ridges may be an adaptation to tougher sclerophyllous vegetation, a reflection of progressive continental aridity during the Cainozoic. In Opalania, the very deep dentary and narrow triturating surface suggest omnivory – a diet of plant material and possibly small molluscs and invertebrates. The triturating surface seems to be very narrow in Sunflashemys, and the articular area resembles that of Elseya, implying that small invertebrates and vertebrates were the food source (Cann 1998).

297 The Lightning Ridge chelid material provides few clues on palaeoecology of the group in this near-polar locality, but these were probably fluviatile forms. It is noted however that very small turtles tend not to inhabit fast-flowing water bodies (White 1997), and the small Lightning Ridge chelids may have favoured shallow or calm enclosed water systems. Biological requirements of Early Cretaceous chelids were probably much the same as extant Australian taxa, which are either carnivorous (Chelodina sp.; Cann 1998) or predominantly herbivorous (Emydura/Elseya; White 1997). Abundant and varied freshwater invertebrates and small vertebrates were a plentiful food source for aquatic adapted species. Early Cretaceous Australian chelids were contending with extreme near-polar climatic conditions as well as a redoubtable range of predators, including large actinopterygians, plesiosaurs, at least three types of crocodylians, and theropod dinosaurs that may have been specialized for hunting in shallow water. The need was great for cryptic behaviours, speed on land and in water, and complete withdrawal of body parts into the shell.

Turtles can survive long periods without food, and at these high palaeolatitudes during the long polar winters, would have hibernated or aestivated in deep mud. Two of the microsites examined in this study (Chapter Ten; sites 34 and 39) produced turtle material in the absence of other vertebrates, and additional locations producing only turtle material have been cited (pers. obs.). Perhaps these were low-energy burials in ponds or still water at some distance from primary palaeochannels, but there is an interesting possibility that these isolated individuals were hibernating or aestivating in the sediments, where they died due to freezing or other stresses. Smaller chelids, or sub-adult animals, may have aestivated communally, as do some extant groups in northern Australia (Cann 1998).

The number of frost-free days in warmer months directly influences success rates of breeding and hatching in turtles. Tiny turtle elements in the assemblages demonstrate that the Lightning Ridge floodplain with its abundance of small water bodies, was an important breeding ground, and meiolanoid-like turtles were breeding at even higher palaeolatitude in the Albian of southern Victoria. Chelycarapookus from the Merino Formation at Casterton, and Otwayemys from Cape Otway are fluviatile forms (Warren 1969; Gaffney et al. 1998). The Eumeralla Formation at Cape Otway

298 comprises deposits that are typical of broad shallow waterways, braided river systems and lakes. Meiolanoid turtles resembling Spoochelys occur in the Aptian Strzelecki Group (Wonthaggi Formation; pers. obs.) which is characterised by thick floodplain deposits and variable flow regimes, including seasonal flash flooding (Vickers-Rich 1996).

Turtle eggs and hatchlings would have been a prime dietary target for carnivorous or omnivorous predators. Ichthyosaurs ate hatchling sea turtles in Early Cretaceous Queensland (Kear et al. 2003). Compression and step fractures caused by predation or scavenging are a feature of at least one turtle bone at Lightning Ridge, and closer inspection of the hundreds of turtle specimens will probably reveal further evidence of predation and predator. Given that dermal and cartilaginous material is preserved, albeit sparsely, it is likely that opalised turtle eggs or at least egg-shell will be found. It would be interesting to know if eggs of the Lightning Ridge meiolanoids were oval and soft-shelled as in modern pleurodiran taxa, or thick-shelled and spherical as in Meiolania.

In summary, the diversity of non-marine turtles in the Early Cretaceous of Lightning Ridge reflects a range of ecosystems and habitats. The meiolanoids were basically land-living turtles, and presence of large carnivorous predators, both terrestrial and aquatic, indicates that structural adaptations for protection and defensive behaviours were developed. This included anterior extension of the carapace, lateral neck retraction, and a powerful tail-swinging capability. In Spoochelys, the dermal skull roof was heavily ossified with bony scutes, and Sunflashemys had defensive scent glands. Dietary requirements of the meiolanoids are unclear; jaw structure in Spoochelys and Opalania suggests omnivory; Sunflashemys may have been the more predatory form. The chelids were most likely opportunistic feeders, both carnivorous and herbivorous, as in modern groups.

Large eye size in Spoochelys may be an adaptive response to polar twilight conditions and turtles would have aestivated or hibernated in deep mud during extreme winters. At other times, as poikilothermic reptiles with high thermal inertia, turtles would rely on sunbaking to maintain core body temperatures. Breeding was governed by seasonal

299 cycles, temperatures effecting duration of incubation and hatchling attributes. Eggs, hatchlings and juveniles would be heavily predated by carnivores and .

300 CHAPTER TWELVE

BIOGEOGRAPHY OF NON-MARINE TURTLES OF EARLY CRETACEOUS AUSTRALIA

The Australian fossil record to date has allowed only a glimpse of the earliest phases of turtle history in the eastern section of Pangea, and biogeography of Mesozoic turtles in this region is very poorly understood. Discovery of at least seven taxa of non-marine turtles in the Albian of Lightning Ridge, New South Wales, confirms the presence of more complex and ancient diversifications in this region than previously indicated. Biogeographic hypotheses are still highly speculative, however, and will be effected profoundly by new fossil discoveries. Impending interpretation and analysis of unstudied material from Antarctica (Jeffrey Stilwell pers. comm.) and from the Strzelecki and Eumeralla Formations of Victoria (Lesley Kool and Gene Gaffney, persn. communs.) will be critical to future discussions. The following preliminary observations are offered in the interim.

Early Cretaceous Australian turtle faunas include terrestrial, freshwater aquatic and marine forms: meiolanoids, chelid pleurodires and protostegids, plus a variety of currently indeterminate groups. PAUP analysis undertaken during this study indicates that phylogenetic affinities of the Australian taxa are with southern hemisphere groups (Fig. 70). This analysis did not resolve relationships of Otwayemys; the possibility of a sister-group relationship with Mongolochelys from Asia is considered inconclusive. Comparable forms and faunas are in Liassic Pangean India (Indochelys); and in South America: - the Late Triassic Los Colorados Formation (Palaeochersis) and the mid-late Jurassic Canadon Asfalto Formation, Argentina (Condorchelys); the Vaca Muerta Formation, Argentina (Notoemys); the Albian Lohan Cura Formation (small chelids cf. Prochelidella); the Early Cretaceous Cerro Barcino Formation of Chubut, Patagonia (Chubutemys) and Santana Formation, Brazil (the protostegid Santanachelys gaffneyi Hirayama 2000); the Late Cretaceous Rio Negro/Los Alamitos (meiolaniids and chelids); and the Eocene Punta Peligro Formation of Argentina (meiolaniids).

301 Identification of meiolanoids and chelids in the Albian of Lightning Ridge suggests a greater uniformity of taxonomic composition across the eastern and western divisions of Gondwana than previously thought. By this time, however, differences had emerged. The South American/South African record includes, in addition, pelomedusoids, podocnemids and primitive cryptodires, forms apparently unknown to date in the Australian Mesozoic. In relation to non-marine turtles, the disparity infers ‘a continental barrier between West and East of Gondwana’ during the Early Cretaceous, promoting the notion of an ‘Occidental’ turtle fauna in South America and an ‘Oriental’ turtle fauna in Victoria, New South Wales and Queensland (Lapparent de Broin and Molnar 2001).

In Patagonia, the southern Gondwanan turtle fauna of meiolaniids and chelids developed from the Late Cretaceous to early Eocene. Palaeogeography of the pelomedusoids, sister-clade to the chelids, is well documented (Lapparent de Broin 2001; Gaffney et al. 2006). Extant pelomedusoids are freshwater forms confined to the southern hemisphere, but fossil taxa were wide-ranging near-shore marine turtles (Nicholls 1997). The ‘formidable’ Early Cretaceous radiations possibly originated shortly before separation of South America and Africa (Lapparent de Broin 2000), when pelomedusoids dispersed northwards from the northern provinces of South America across Africa, southwestern Europe and India (de Broin and de la Fuente 1993; Lapparent de Broin 2001). From the Early Cretaceous onwards, pelomedusoids are known from South America, Africa, Europe, Asia and North America, excluding only Antarctica and Australia - and their absence from the Australian record is anomalous, to say the least. Primitively they may have been temperate or tropical forms, diversifying mainly during periods of high global temperatures. Presumably geographic and climatic barriers prevented dispersal into southeastern Gondwana not only of pelomedusoids, but also the non-marine cryptodiran groups.

Distribution of extant turtles is governed by climate and because the most likely distribution pathway during the Mesozoic was so far to the south, climate may have been crucial to interchange between Australia and other Pangean/Gondwanan sectors. Ectothermic reptiles in general appear to be barred from polar distribution

302 at a coldest month mean temperature of ~ 5.5oC (Brinkman and Tarduno 2003). High temperatures in the Eocene are cited as a critical factor allowing interchange of turtle assemblages between Asia and North America at that time (Brinkman 2005). During the Albian, high temperatures may have permitted faunal movement between South America and Australia across Antarctica, through the southern sector of Gondwana. Preceding and subsequent to the Albian, faunal exchange at these higher palaeolatitudes was likely reduced or prevented during episodes of colder global climates.

Although the Aptian-Albian record in Australia comprises fewer major turtle groups than western Gondwana, radiations within those groups are distinctive and endemic. Presence of a number of relic vertebrate groups (this volume; Rich et al. 1988; Woodburne et al. 2003; Thulborn and Turner 2003; Kear 2006) implies that restrictions to faunal movement may have been in place from the mid-Jurassic or earlier. The Lightning Ridge meiolanoids may be descendents of very ancient forms that were established widely across Pangea during the Early Mesozoic. Phylogenetic affinity between the Lightning Ridge meiolanoids and archaic turtles from South America, South Africa, India and Europe suggests that during the early Mesozoic, turtles that were more closely allied with pleurodiromorph stem groups than with cryptodires enjoyed a near world-wide distribution, spanning both hemispheres. The meiolanoids may have originated in Pangea and were apparently restricted to the southern hemisphere after the mid-Jurassic.

Palaeogeographic reconstructions (Veevers 2001) show that early Mesozoic exchange routes during periods of global cooling may have been through those sections of Pangea that later separated out as Africa, Madagascar and India. Biogeographic evidence for this is provided by Indochelys, the nearest southern hemisphere turtle record to Early Cretaceous Australia. India began to rift from Africa, Australia and Antarctica during the Late Jurassic, and structural affinity between Indochelys and Chelycarapookus from the Albian of Victoria, reinforces the likelihood of an early Mesozoic origin for the relic Australian taxa.

Apart from Proganochelys from Germany, turtles identified as proganochelyids occur in the Late Triassic of East Greenland (Jenkins et al. 1994), Thailand (de

303 Broin et al. 1982; de Broin 1984) and possibly Mexico (Lucas et al. 2000). Priscochelys hegnabrunnensis Karl 2005, a possible sister taxon to Proganochelys, is known from Middle Triassic Germany (235 my; Rieppel and Reisz 1999; Joyce and Karl 2006). Sparse as they are, these records suggest that proganochelyids were confined to Europe and Laurasia (Fig. 70). A geographical barrier to southern dispersal of the proganochelyids is inferred, and a more limited distribution than for pleurodiromorph taxa.

The platychelyids, united with chelids and pelomedusoids in the Megapleurodira (Gaffney et al. 2006), were near-shore marine forms (Gaffney et al. 2006). The fossil record demonstrates widely dispersed and vicariant radiations of platychelyids on three continents (South and Middle America, Europe and Africa) from the mid- Jurassic to Late Cretaceous. Diversity and broad distribution of chelids and pelomedusoids (pelomedusids + podocnemids) by the Aptian-Albian in South America suggests that the basal eupleurodiran divergence occurred much earlier in the Jurassic (Lapparent de Broin and de la Fuente 2001).

The Chelidae is a Gondwanan group that probably originated in the southern South America/Antarctica/Australia block (de la Fuente 2003). Affinities of the Lightning Ridge chelids are uncertain and at this stage it is unclear if South American groups are represented. Chelids are more cold-adapted than pelomedusoids, hence the more southern distribution (Lapparent de Broin 2001; Lapparent de Broin and Molnar 2001), but the diaspora would have been limited by intolerance of salt water and climatic extremes.

The protostegid sea turtles (Chelonioidea) were uneffected by the biological or geographical impediments that excluded the marine pelomedusoids from southeastern Pangea. Protostegids were well advanced by the Aptian-Albian when at least five lineages had developed (Hirayama 1998; Kear and Lee 2006); and were widely dispersed during the Cretaceous (Wiffen 1981; Hirayama 1994, 1997). These marine cryptodires are abundant in Early Cretaceous Queensland (Fig. 1) but unknown in slightly older, colder localities of South Australia, possibly due to the higher palaeolatitude and deeper marine offshore deposition (Kear 2003). Evidence of protostegids is absent, so far, from Lightning Ridge.

304 Commenting on the disjunctive distribution of the horned turtles, some palaeontologists have proposed that meiolaniids floated or rafted between islands (Anderson 1925; Simpson 1938; Mittermeier 1987). The distribution pattern of Meiolania is attributed to Mesozoic vicariance and ‘escalator hopscotch’, a geological model that explains the occurrence of archaic fauna on young oceanic islands. Briefly, as the lithosphere traverses hot spots in the mantle, island chains are created when seamounts progressively form and submerge, permitting transfer of fauna over small oceanic distances (McDougall et al. 1981; and McKenna 1983, cited by Gaffney 1983). In this context, it is intriguing that adaptive structures that may have facilitated flotation are seen in carapace material of meiolanoid taxa from Lightning Ridge, and in Meiolania and Proganochelys. Perhaps the ability to float over large distances was crucial to dispersal of certain primitive turtle groups.

Chelid history spans ~150 my (Jurassic-Recent), an extraordinary evolutionary trajectory; but the Meiolanoidea, with a Triassic-Holocene biochron, may have been the longest surviving turtle group. Meiolaniid scraps from Pindai Cave, Nepoui Peninsula of mainland New Caledonia are associated with fossils that are charcoal-dated to 1720 + 70 years BP (Balouet 1991; Gaffney 1996). Faunal elements from Pindai Cave are contemporaneous with cooking fires, suggesting human involvement in the extinction of at least one species of meiolaniid (Gaffney et al. 1984; Molnar 1991).

Low taxonomic diversity of the Australian turtle fauna persists even today. Several groups of sea turtles (Chelonioidea) inhabit coastal waters of northern Australia. The Australian trionychid record extends from the Eocene to Pleistocene and the monotypic cryptodire Carettochelys insculpta Ramsay 1886 is known from the Northern Territory. The trionychids and Carettochelys may be Asian Tertiary immigrants, but otherwise there were apparently no incursions of non-marine forms from at least the Early Cretaceous to the present. All extant taxa are chelid pleurodires and today the turtle fauna at Lightning Ridge consists entirely of chelids (Chelodina, Elseya and Emydura sp.).

305 In summary, Early Cretaceous Australian turtle faunas include meiolanoids, chelid pleurodires, protostegids and additional groups that are currently indeterminate. Taxonomic diversity is higher, and similarity to turtle faunas of South America is greater than previously thought. The meiolanoids appear to be Triassic-Jurassic relics, and comparative morphological and biogeographic data suggests a diversity of these ancient forms widely distributed across Pangea. Prior to the Late Jurassic, faunal exchange into Australia could have been by way of the African and Indian landmass components; and during the Albian, high global temperatures may have permitted interchange through Antarctica.

Chelids and protostegids may be Late Jurassic-earliest Cretaceous immigrants from other Gondwanan sectors, but the degree of regional endemism suggests the Australian Aptian-Albian radiations were the result of prolonged geographic isolation. Occurrence of chelids in southeastern Gondwana in the Albian supports the likelihood of monophyletic origin of South American and Australian chelids, and vicariant evolution of both groups long before the actual physical rupture of the South American and Antarctica/Australian sectors of Gondwana.

306 CHAPTER THIRTEEN

POSSIBLE TRIASSIC ORIGIN FOR THE HORNED TURTLES (MEIOLANOIDEA) AND IMPLICATIONS FOR TURTLE RELATIONSHIPS

Although investigation of turtle ancestry is far beyond the scope of this study, a few speculative comments on this topic appear to be warranted. The following observations are based on examination and analysis of the Lightning Ridge spoochelyids and the meiolaniids (Niolamia L.1418 and Meiolania specimens from Lord Howe Island); and literary comparisons (Gaffney 1979, 1983, 1990).

The subject of turtle origins and relationships is one of the enduring unresolved issues in palaeontology. Putative turtle sister groups are parareptiles, in particular, dwarf parieasaurs (Lee 1995, 1996, 1997; Kordikova 2002), procolophonids (Reisz and Laurin 1991; Laurin and Riesz 1995), sauropterygians (Rieppel and De Braga 1996; De Braga and Rieppel 1997), lepidosaurs (Hill 2005), and saurians - the archosaurian crocodiles and aetosaurs (Hedges and Poling 1999). In fact, just about every group, at one time or another, has been suggested.

The phylogenetic analysis discussed in Chapter Nine was undertaken before descriptions were published of the basal turtles Odontochelys semitestacea Li et al. 2008, Chinlechelys tenertesta Joyce et al. 2008, and Eileanchelys waldmani Anquetin et al. 2008. Odontochelys (Late Triassic, China), now the oldest known and most primitive turtle, is apparently marine, with a formed plastron but carapace elements consisting only of neural plates that are separate from the vertebrae. Odontochelys is presented by its authors as confirming an aquatic origin for turtles and development of the turtle shell from the endoskeleton, not by fusion of osteoderms. In what seems a direct contradiction, Chinlechelys (Late Triassic, New Mexico) supposedly reinforces a terrestrial origin, showing that the earliest turtles were encased in rows of thin dermal armour and that costal plates ossify as independent elements (Joyce et al. 2008). Eileanchelys (Middle Jurassic, Scotland)

308 indicates that some stem turtles were aquatic, rather than terrestrial. These new records demonstrate all too convincingly that Early Mesozoic turtles were as varied structurally and biologically as their modern counterparts, and that an enormous swathe of turtle evolutionary history remains unseen.

In recent phylogenetic analyses, Proganochelys is accepted as sister taxon to all remaining turtles (Gaffney et al. 2006; Sterli et al. 2007). Proganochelys was the outgroup in the analysis conducted in the course of this present study, results of which suggest that Proganochelys may fall outside a clade containing Palaeochersis and Proterochersis, which is sister clade to the Meiolanoidea. The close phylogenetic relationship between two ancient turtle groups, and a clade consisting of the Lightning Ridge taxa and meiolaniids, is consistently supported in the majority of trees. This morphological evidence, the fact that meiolanoids were diverse and abundant in Early Cretaceous Australia, and that meiolanoid-like forms were widespread across Pangea, infers that Meiolanoidea is a Triassic group.

A number of archaic features in the Meiolanoidea, known from Spoochelys and/or Meiolania, are not seen in Proganochelys. This provides tantalizing evidence that Proganochelys may be closer to forms such as Kayentachelys than to Palaeochersis and Proterochersis. Primitive amniote features in the Meiolanoidea include: integration of cranial scutes and underlying bones; vestigial pineal or parietal concavity towards posterior of midline parietal suture (Spoochelys); and postorbital-quadratojugal contact, supratemporal-postorbital contact, possible presence of tabulars and postfrontal (Spoochelys); basisphenoid-epipterygoid contact (basipterygoid process from basisphenoid may have articulated with epipterygoid?); stapedial foramen and stapedial canal; vagus nerve passed between basioccipital and exoccipital; coronoid medial wall to fossa meckelii; possible presence of postsplenial or preangular; atlantal ribs; and large cavities above postzygapophyses in rear cervical vertebrae. These features are not recorded in Proterochersis, and are not reported in Palaeochersis or in any northern hemisphere group; and it is unclear if they occur in newly-discovered basal taxa.

The turtle progenitor was a small, massively-built reptile, either terrestrial (Joyce and Gauthier 2004; Joyce et al. 2008) or aquatic (Li et al. 2008), with a typical

309 predominantly lateral mode of axial movement. The turtle ancestor may have exhibited some of the following features, which are variably developed in Proganochelys, australochelyids and Meiolanoidea: box-like skull with pronounced angle between skull roof and cheek; Prominent supraorbital ridges and tuberosities; Skull roof heavily ossified with tuberculate surface texture, spikes or bosses; Skull scales X, G, D (after Gaffney 1990, 1996); Postparietal present; Inner skull roof with inflated ?pineal cavity on dorsal midline (marking expanded diencephalon?); Large nasal bones; Large lacrimal bone and lacrimal duct; Deep cheek flanges formed primarily by quadratojugal; Supratemporal relatively large and perhaps tuberous or prominent; Palatal teeth on vomer, pterygoid and palatine; Kinetic basicranium (moveable basipterygoid articulation); Large interpterygoid vacuity, possibly quite wide and U-shaped anteriorly; Parasagittal palatal perforations; Division between palatine and carotid arteries outside braincase; Primary neurocranium (basisphenoid and basioccipital) massively thick; Rostrum basisphenoidale dorsally inflected; Passage of canalis caroticus internus steeply inclined within basisphenoid; Jaw adduction mechanics involving front side wall of braincase; Very large epipterygoid; Middle ear without bony floor; Quadrate process of pterygoid elongated, forming a vertical wall along ventromedial face of quadrate; Massive stapes; Foramen jugulare anterius very large; Splenial reaching symphysis and extending to ventral rim of jaw ramus; Large cervical ribs, deep dorsoventrally, along entire cervical series; Eighth cervical vertebra with massive transverse processes;

310 Very large transverse processes on anterior caudals; Tail very long, broad anteriorly; Posterior of tail deep dorsoventrally; Tail club formed by dermal ossifications (spikes, rings or sheaths); Large clavicles (cleithra), interclavicles and gastralia; Scapular spine long and circular in section; Short hands and feet; Metacarpals and metatarsals with pronounced proximal overlap, possibly developed as tubercles; Proximal articulations of first manual and pedal phalanges forming deep circular acetabula, extended posteroventrally; Broad, robust unguals.

Any new insights into turtle origins will be critical to future phylogenies. An expanded cladistic analysis that includes hypothesized turtle outgroups and structural information from newly described basal taxa, and recognizes the Meiolanoidea as a Triassic group, may well elucidate aspects of turtle origins and produce more stability in relation to Early Mesozoic stem turtles.

311 CHAPTER FOURTEEN

CONCLUSIONS

Non-marine turtle faunas of eastern Gondwana exhibit higher taxonomic diversity and greater similarity to turtle faunas of South America, than previously thought. Identification and interpretation of fossil turtles from Lightning Ridge, New South Wales, has prompted comparison with Mesozoic groups that are widely separated in space and time. This process has significantly augmented information on turtle evolution in Mesozoic Australia.

Prior to this study, only two non-marine turtles from Early Cretaceous Australia were formally described, both from Victoria. Lightning Ridge has yielded up to seven taxa – evidence of at least two indeterminate chelid pleurodires, additional groups of uncertain affinities, and three new primitive meiolaniid-like forms - Spoochelys ormondea, Sunflashemys bartondracketti and Opalania baagiiwayamba. Multiple shared derived features attest to a close phylogenetic relationship with the Tertiary horned turtles and these three taxa are assigned to the new family Spoochelyidae, sister-group to Meiolaniidae, in the superfamily Meiolanoidea.

Turtle remains at Lightning Ridge are found in deeply weathered claystone sediments representing wetlands and waterways of a broad coastal delta. This study includes a comprehensive survey and description of the Lightning Ridge fossil locality. Various collection methods were employed, producing 40 sample assortments from known locations, and from discrete unprovenanced sites. The middle Albian assemblages comprise freshwater aquatic invertebrates and vertebrates, terrestrial vertebrates from floodplain habitats, and sparse elements of marine groups.

The abundance of opalised and lithified plant debris in the opal-bearing levels attests to the high biomass component of the Finch Clay Facies, evidence of a

312 tight physical and geochemical nexus between organic material and opal. Palaeochannels correlate with centers of silica precipitation, and historically, fossil collection at Lightning Ridge has been incidental to opal mining, rather than by means of conventional scientific exploration and excavation. Opalised specimens that are of global scientific importance - monotreme mammal jaws and bird material, for example - have been found in sediments extracted by opal miners. Mullock, tailing heaps and silt tank residues are vital repositories of palaeontological data; excavated sediments contain fossil material even after being processed mechanically and searched for opal by miners.

Fossils occur at almost every location where opal-bearing sediments are brought to the surface, over an area of more than 1500km2. Fidelity of sampling from surface locations is a measure of the number of search hours at that site. Tailing heaps are concentrations that represent greater spatial coverage of the biofacies, and therefore provide a greater diversity and quantity of fossil material per unit of search time than mullock or silt in the settling tanks. As might be expected over this enormous locality, spatial densities of fossils are hugely variable. Tonnes of claystone may produce no fossils, other sites yield plant material only, or multiple bone elements.

In general, opal miners’ collections are imprecise, highly biased samplings that do not reflect taxonomic diversity, species composition or faunal size range. Articulated and associated elements of a greater number of groups, including microvertebrates, are retrieved when sediments that include the smallest fractions are searched methodically. The full extent of taxonomic diversity and an accurate picture of faunal composition over this vast locality are yet to emerge.

Lightning Ridge is one of the most diverse Early Cretaceous localities in Australia and is among the world’s most productive near-polar vertebrate sites. The locality holds enormous potential for future palaeontological work. Biodiversity is exceptionally high – 28 named taxa; and many more that are undescribed, unstudied and undocumented. The invertebrate fauna consists of up

313 to fifteen taxa of bivalve molluscs; at least five families of freshwater gastropods, including viviparids that are among the oldest in the world; and freshwater crayfish. Vertebrate groups include chondrichthyans; anguilliformes (the oldest known eel skull); actinopterygians and lungfish; Australia’s oldest anuran; sauropterygians; squamata (a snake); three crocodylians; and pterosaurs. Prosauropods, sauropods, hypsilophodontids, a muttaburrasaurus and ornithomimosaurid and dromaeosaurid theropods, and at least two ornithoracine birds are recorded. Stegosaurids, spinosaurids, abelisaurids and an alvarezsaurid may be present. The locality has produced an unprecedented array of up to five taxa of monotreme mammals, a possible synapsid and evidence of at least one other mammal group.

During the Early Cretaceous, eastern Australia lay at palaeolatitudes of ~60- 70oS. Mild palaeoclimates are inferred by presence of temperate and subtropical forms like viviparid snails, freshwater crayfish, lungfish, anurans, turtles, crocodiles and sauropod dinosaurs. High summer rainfall and strong seasonality, cool to very cold winter temperatures and months or weeks of polar twilight or complete darkness suggest a palaeoenvironment without modern equivalent. Endothermy, enhanced optical acuity and electrosensory capabilities in at least three groups that are especially diverse at generic and species level (turtles, hypsilophodontid dinosaurs and monotreme mammals) may be adaptations to extreme climatic conditions. Biological strategies such as burrowing, aestivation, hibernation, seasonal nomadism and migration may have been vital. Warmer summer conditions would attract nomadic herbivores, and it is likely that synchronized seasonal breeding of crayfish, lungfish, turtles and crocodylians provided an abundant annual food source for aquatic and terrestrial predators, migratory species capable of aquatic hunting, and, more rarely, marine ‘invaders’ of freshwater systems.

The Lightning Ridge chelids are Australia’s oldest, the first pre-Eocene record for this group outside South America. The most southern known occurrence for chelids, at higher palaeolatitude than records from the Albian of Patagonia, this new record demonstrates that chelids were widely dispersed across the polar

314 supercontinent by the Albian and that their evolutionary history in Australia and South America was protracted and multiform. A Pangean origin, possibly in the Late Jurassic or even earlier, is inferred. It is unclear as yet if the Lightning Ridge chelids represent new groups or South American clades previously unknown in Australia, and generic diagnosis awaits discovery of further fossil specimens. It seems likely that fossil data will eventually confirm vicariant radiations pre-dating the actual physical rupture of the Pangean continental plates.

Small to middle sized forms, the Lightning Ridge meiolanoids were land turtles with high-domed carapaces, robust and tightly-bound lower podial elements, and very short hands and feet. The chelids were rather small and probably fully aquatic. The palaeolatitude suggests that these turtles were close to their thermal limits. Large eye size in Spoochelys may be an adaptive response to polar twilight conditions, and turtles would have aestivated or hibernated in deep mud during the winter. At other times, as poikilothermic reptiles with high thermal inertia, turtles would have relied on sunbaking to maintain core body temperatures. Breeding was governed by seasonal cycles, temperatures effecting duration of incubation and hatchling attributes. Eggs, hatchlings and juveniles would have been heavily predated by carnivores and omnivores. The range of predators in the assemblage, both terrestrial and aquatic, implies that the turtles had developed protective structural and behavioural adaptations. In the meiolanoids, this included anterior extension of the carapace, lateral neck retraction, and a powerful tail-swinging capability. In Spoochelys, the dermal skull roof was heavily ossified with bony scutes, and enlarged scent glands in Sunflashemys probably served a defensive role, as in modern chelids.

Results of this study support the hypothesis that the Lightning Ridge land turtles and meiolaniids are archaic stem taxa. In rebuttal of previous endeavours linking the meiolaniids to Laurasian groups, this present search has lead inexorably to ancient southern hemisphere records, and it is Pangean turtles that are crucial to resolution of affinities.

315 According to a phylogenetic analysis, australochelyids and Proterochersis are sister- group to a clade containing Indochelys from India, Chubutemys from Patagonia, and the meiolanoids (Spoochelyidae, Chelycarapookidae and Meiolaniidae). Although relationships of Otwayemys from Cape Otway are uncertain, it seems that further meiolanoid taxa, in addition to Chelycarapookus and NMVP19057, occur at Early Cretaceous sites in Victoria.

This analysis implies that the Australian taxa are not closely related to cryptodires or eucryptodires, or to the Pleurodira. All the same, they are resolved as sister group to a clade containing Palaeochersis and Proterochersis, and it is generally accepted that Proterochersis is the most basal pleurodire (Joyce 2007; Sterli et al. 2007; Gaffney et al. 2006, 2007). Meiolanoids are excluded from the Pleurodira on presence of the epipterygoid, cervical ribs and opisthocoelous caudals, among other features. Nonetheless, they exhibit a limited quota of derived features which might be expected in basal forms that are closer to pleurodires than to cryptodires. Notwithstanding the copious amounts of missing data and the need for finessing of characters for basal groups, the hypothesis that the Lightning Ridge taxa and meiolaniids share common ancestry with pleurodiran stem taxa rather than with cryptodires is the most plausible explanation of relationships.

For over thirty years, monophyly of the Pleurodira, a group distinguished by lateral neck-bending capacity, has been supported by features of the jaw trochlear, basicranium and pelvis, rather than cervical morphology. This analysis has not succeeded in extracting unambiguous synapomorphies from the complicated series of minor and apparently syncopated adjustments basic to lateral neck movement. However when the essential components of a pleurodiran function are present and the cryptodiran derivations are not, then surely the turtle is a pleurodire. As a corollary, given evidence of phylogenetic affinity with Proterochersis, it seems more parsimonious to conclude that the Lightning Ridge taxa and meiolaniids - and hence the australochelyids - are pleurodiromorph or proto-pleurodiran groups, rather than to assume that a predominantly lateral mode of neck retraction developed twice in turtles. As pleurodiromorphs,

316 meiolanoids are the most primitive known ‘side-necked’ turtles in which cranial structures and postcrania other than the shell are preserved.

This interpretation, if correct, positions the primary casichelydian dichotomy much earlier than previously thought, perhaps as far back as the mid- Triassic. Pleurodiromorph turtles occupied both hemispheres and four continents by the Late Triassic, an interesting contrast to records for proganochelyids which are restricted to Europe and Eurasia, inferring a geographical barrier to southern dispersal of proganochelyids.

Australian Early Cretaceous vertebrate faunas are characterized by relic populations and local and regional endemics, symptomatic of geographic isolation in the southeastern province of Gondwana. Pleurodiromorph distribution in the Early Mesozoic may have included south polar regions during periods of high global temperatures, however Indochelys from the Indian Liassic provides evidence that in colder periods, faunal exchange between east and west Pangea may have been through the African and Indian landmass components, rather than across higher palaeolatitude Antarctica. Warm global temperatures during the Albian probably permitted interchange between east and west Gondwana across Antarctica, but the high degree of endemism suggests that, for some Australian groups, biogeographic isolation commenced very early in the Jurassic, if not before. On the whole, faunal links are demonstrably with Pangea and western Gondwana, not with Laurasia and North America.

Evolutionary persistence is a salient feature of many Mesozoic Australian taxa, particularly the turtles. Chelids have survived for perhaps 150 my and meiolanoids were ‘Triassic-type’ forms, occupying the Australian landmass and Pacific Islands for up to 200 my, the greatest biochron for any turtle group. The most recent remains of horned turtles are associated with cooking fires in the Pacific islands. Humans are implicated in the demise of this most venerable turtle lineage.

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351 APPENDIX 1.0

PHYLOGENETIC ANALYSIS – PAUP DOCUMENTATION CHARACTER SET

1. Cranial scute sulci: (0) undefined or poorly defined; (1) strongly incised. 2. Relationship of cranial scutes and underlying bones: (0) scute and bone not histologically unified; (1) scute and bone integrated. 3. Layout of scute pattern: (0) X small, G and D present; (1) X small and G, D, B, C, H, E, J, K and I present; (2) X large and G, D, B, C, H, E, J, K and I present; (3) any other pattern or no pattern. 4. Premaxilla, midline dorsal process: (0) present; (1) absent. 5. Nasal bones: (0) present; (1) absent. 6. Nasal bones, dorsal exposure: (0) small to large dorsal exposure; (1) very large dorsal exposure. 7. Height of narial aperture: (0) low; (1) level with top of orbit. 8. Fossa nasalis (internal choanae): (0) very large, open ventrally; (1) reduced, open ventrally; (2) reduced, closed ventrally. 9. Narial platform or thickening: (0) absent; (1) present. 10. Large prefrontal (interorbital) bosses and prominences: (0) present; (1) absent. 11. Lacrimal bone: (0) present; (1) absent. 12. Lacrimal duct: (0) formed in lacrimal bone; (1) formed in nasal and maxilla; (2) lacrimal duct fully closed (absent). 13. Vomer: (0) paired; (1) single. 14. Medial meeting of prefrontals: (0) absent; (1) present. 15. Prefrontal-vomer contact: (0) absent; (1) present. 16. Palatal surface: (0) palatal teeth on vomer, palatine and pterygoid; (1) palatal teeth on pterygoid; (2) palate smooth. 17. Maxilla: (0) deep below orbit; (1) narrow below orbit. 18. Deep cheek flanges formed by jugal and quadratojugal: (0) absent; (1) present. 19. Frontal contribution to orbit: (0) absent due to prefrontal-postorbital contact; (1) present. 20. Postparietal: (0) present; (1) absent. 21. Supratemporal: (0) present; (1) absent. 22. Supratemporal shape: (0) wider than long; (1) elongate; (2) subcircular. 23. Contact of supratemporal with postorbital and quadratojugal: (0) absent; (1) present.

352 24. Squamosal-parietal contact: (0) present; (1) absent. 25. Position of squamosal-parietal contact relative to supratemporal: (0) mostly anterior to supratemporal; (1) mostly posterior to supratemporal. 26. Squamosal-parietal contact in turtles lacking the supratemporal: (0) extensive; (1) short or absent. 27. Supraoccipital exposure on skull roof partly dividing parietals: (0) no; (1) yes. 28. Supraoccipital crest: (0) absent; (1) present. 29. Vertical curtain of bone partly closes rear temporal fossa: (0) absent; (1) present. 30. Interpterygoid vacuity: (0) present; (1) absent. 31. Shape of interpterygoid vacuity: (0) rostrocaudal and dorsoventral opening between pterygoid and rostrum basisphenoidale; (1) dorsoventral opening that is predominantly transverse between pterygoid and rostrum basisphenoidale. 32. Basisphenoid-basioccipital medial process: (0) unpaired; (1) paired. 33. Condylus mandibularis position: (0) posterior to basisphenoid-basioccipital suture; (1) near or in line with basisphenoid-basioccipital suture; (2) anterior to basisphenoid-basioccipital suture. 34. Processus trochlearis pterygoidei: (0) absent; (1) present. 35. Processus trochlearis oticum: (0) absent; (1) present. 36. Vertical parasagittal plate on transverse pterygoid process: (0) absent; (1) present. 37. Pterygoid, posteroventral flange along lateral edge, medial to transverse pterygoid process: (0) absent; (1) present. 38. Epipterygoid: (0) present; (1) absent. 39. Epipterygoid structure: (0) with dorsolateral flange into subtemporal fossa, foramen nervi trigemini unformed; (1) with dorsolateral flange into subtemporal fossa, foramen nervi trigemini developed; (2) without dorsolateral flange, foramen nervi trigemini developed. 40. Epipterygoid and prootic for foramen nervi trigemini, epipterygoid forms posterior margin of foramen interorbitale: (0) no; (1) yes. 41. Processus inferior parietalis: (0) undeveloped; (1) slightly developed; (2) developed. 42. Acute quadrate margin: (0) absent; (1) present. 43. Cavum tympani: (0) absent; (1) small or moderately developed; (2) deeply excavated.

353 44. Precolumellar fossa: (0) absent; (1) present. 45. Eustachian tube within incisura columellae auris: (0) absent; (1) present. 46. Antrum postoticum: (0) unformed; (1) formed. 47. Cranioquadrate space or canalis cavernosus: (0) cranioquadrate space opens ventral to fenestra ovalis; (1) canalis cavernosus large, opens ventral to fenestra ovalis; (2) canalis cavernosus reduced, opens dorsal to fenestra ovalis. 48. Quadrate, medial process contacting braincase elements and underlying cranioquadrate space: (0) absent; (1) present. 49. Ventral exposure of prootic: (0) not concealed by pterygoid; (1) partly concealed by pterygoid; (2) fully concealed by pterygoid. 50. Basisphenoid ventral outline: (0) elongate not sutured to pterygoids; (1) more triangular; (2) more pentagonal. 51. Basisphenoid, basioccipital cross section: (0) very thick; (1) thinner. 52. Ventral exposure of basisphenoid: (0) narrow, less than one third of skull width; (1) broad, one third or more of skull width. 53. Basipterygoid process and basipterygoid articulation: (0) basipterygoid process present with a moveable basipterygoid articulation; (1) basipterygoid process present with a sutured basipterygoid articulation; (2) basipterygoid process absent and sutured basipterygoid articulation. 54. Pterygoid sutured to posterolateral section of basisphenoid and anterolateral section of basioccipital: (0) no; (1) yes. 55. Inner ear or cavum labyrinthicum: (0) floored by prootic/opisthotic or basisphenoid/opisthotic; (1) open ventrally, margins formed by prootic, opisthotic, basisphenoid and basioccipital; (2) floored by prootic and/or quadrate; (3) with pterygoid margin or floored by pterygoid. 56. Extended basisphenoid margin of open cavum labyrinthicum: (0) absent; (1) present; (2) present, with margin formed by posterolateral shelves of basisphenoid dorsal to ventral surface of basicranium. 57. Hyomandibular branch (VII) of facial nerve: (0) traverses cranioquadrate space (canalis cavernosus); (1) separated by bone from cranioquadrate space (canalis cavernosus). 58. Foramen posterius canalis carotici laterale in suture between medial margins of pterygoids and anterior section of rostrum basisphenoidale: (0) no; (1) yes.

354 59. Foramen basisphenoidale: (0) formed by basiphenoid, equals fpcci; (1) formed by basisphenoid and pterygoid, equals fpcci; (2) formed by basisphenoid and pterygoid, more posterior fpcci present; (3) absent due to prootic forming fpcci. 60. Foramen posterius canalis carotici interni: (0) foramen caroticum basisphenoidale; (1) formed in part by basisphenoid; (2) formed entirely by pterygoid; (3) formed by prootic. 61. Foramen posterius canalis carotici interni: (0) not formed by basisphenoid and pterygoid; (1) formed by basisphenoid and pterygoid, located midway along basiphenoid-pterygoid suture. 62. Recessus scalae tympani: (0) unformed; (1) formed, unclosed ventrally; (2) formed, closed ventrally. 63. Foramen jugulare posterius: (0) absent; (1) present. 64. Large splenial extending to lower jaw rim: (0) present; (1) splenial reduced; (2) splenial absent. 65. Contact of splenial and dentary in meckelian sulcus anterior to foramen intermandibularis medius: (0) no; (1) yes. 66. High vaulted domed carapace: (0) absent; (1) present. 67. Curvature of anterior carapace margin: (0) transverse or indented; (1) rounded, midline area extends forward. 68. Prominent or bulbous cervical scute: (0) absent; (1) present. 69. Anal notch separating rear marginals: (0) present; (1) absent. 70. Lateral edge of forwardly curved anal notch forms posterior limit of carapace: (0) no; (1) yes. 71. Nuchal articulation with eighth cervical vertebra: (0) facet elongate; (1) circular nubbin. 72. Vertebral scutes: (0) broad; (1) very broad due to narrowing and elongation of pleural scutes; (2) narrow. 73. Distal ends of costal ribs fitted between contiguous bridge peripherals: (0) absent; (1) present. 74. Suture between pygal and suprapygal V-shaped posteriorly: (0) absent; (1) present. 75. Neural count: (0) more than eight; (1) eight or less. 76. First vertebral: (0) transverse anterior margin, straight lateral margins; (1) strongly curved, semicircular anterior margin.

355 77. Position of vertebral III/IV sulcus in turtles with five vertebrals: (0) across neural six; (1) across neural five. 78. Supramarginal scutes: (0) full set (12); (1) less than five; (2) absent. 79. Infarmarginals: (0) present; (1) absent. 80. Costo-vertebral tunnel: (0) wider anteriorly and posteriorly; (1) wide; (2) reduced. 81. Costals: (0) nine; (1) eight. 82. Carapace-plastron connection: (0) sutured; (1) ligamentous. 83. Gular points of plastron: (0) present; (1) absent. 84. Entoplastron, anterior section: (0) reaches front of plastron dorsally and ventrally; (1) reaches front of plastron dorsally but not ventrally; (2) does not reach front of plastron. 85. Entoplastron, posterior section: (0) elongate, reaches level of axillary notch; (1) shortened. 86. Epiplastra: (0) epiplastra extend posterior to widest part of entoplastron; (1) epiplastra very elongated beyond widest part of entoplastron; (2) epiplastra do not extend posterior to widest section of entoplastron. 87. Axillary buttress: (0) short; (1) elongated anteriorly and tightly curved. 88. Mesoplastra: (0) present; (1) absent. 89. Mesoplastra, size: (0) midline contact; (1) no midline contact. 90. Xiphiplastron: (0) undivided at rear; (1) bifid posteriorly. 91. Fusion of atlantal vertebral elements: (0) no; (1) yes. 92. Cervical articulations: (0) unformed; (1) formed. 93. Fourth cervical articulation: (0) biconcave; (1) opisthocoelous or procoelous; (2) biconvex. 94. Fifth cervical articulation: (0) biconcave; (1) opisthocoelous or procoelous; (2) biconvex. 95. Seventh cervical articulation: (0) biconcave; (1) opisthocoelous or procoelous; (2) biconvex. 96. Eighth cervical articulation: (0) biconcave; (1) opisthocoelous or procoelous; (2) biconvex. 97. Posterior central articulations at rear of cervical series: (0) wide, subcircular or oval; (1) narrow, laterally compressed or triangular. 98. Cervical ribs: (0) present; (1) absent.

356 99. Cervical ribs, size and shape: (0) large; (1) very large and paddle-like. 100. Rear cervicals, deep cavity in neural arch above postzygapophyses: (0) absent; (1) present. 101. Size of cervical parapophyses: (0) do not extend anterior to central articulation facet; (1) extend anterior to central articulation facet. 102. Transverse processes, cervical vertebrae: (0) middle of centrum; (1) front of centrum. 103. Cervical postzygapophyses extended posterodorsally on elevated neural arch: (0) no; (1) yes. 104. First thoracic articulation facet, shape: (0) taller than wide; (1) wider than tall. 105. First thoracic rib: (0) very large; (1) smaller than second thoracic rib. 106. First thoracic rib, costal attachment: (0) not fused to overlying costal; (1) fused to overlying costal. 107. Tenth thoracic vertebra integrated with sacrum: (0) no; (1) yes. 108. Tenth thoracic ribs: (0) osseous attachment to carapace; (1) osseous attachment to carapace and ilium; (2) disengaged from carapace. 109. Sacro-caudal vertebra (last caudal integrated with first caudal: (0) absent; (1) present. 110. Anterior caudal centra: (0) amphicoelous; (1) opisthocoelous; (2) procoelous. 111. Caudal articulations: (0) unformed; (1) predominantly opisthocoelous; (2) mixed procoelous/opisthocoelous or predominantly procoelous. 112. Chevrons: (0) present on nearly all caudals; (1) absent or poorly developed along posterior caudals. 113. Caudal ossification (tail club): (0) present; (1) absent. 114. Cleithra: (0) present; (1) absent. 115. Cleithral ventral structure: (0) single transverse base; (1) separate paired bases. 116. Acromial process: (0) triradiate in section and short; (1) triradiate in section and long; (2) not triradiate in section. 117. Coracoid foramen: (0) present; (1) absent. 118. Acromion, distal section withposterolateral spike: (0) absent; (1) present. 119. Olecranon process of ulna: (0) low to medium in height; (1) very high. 120. Dorsal ridge of proximal ulna shaft: (0) weak to medium development; (1) very pronounced.

357 121. Connection of pelvis to carapace and plastron: (0) ligamentous; (1) partly sutured; (2) fully sutured. 122. Ventral ischial tubercle: (0) present; (1) absent. 123. Hypoischium: (0) present; (1) absent. 124. Phalangeal formula: (0) most digits with two short phalanges; (1) most digits with three long phalanges. 125. Reduction or loss of fifth digit phalanges: (0) no; (1) yes.

358

APPENDIX 2.0

LIGHTNING RIDGE FOSSIL FLORA AND FAUNA SURVEY

APPENDIX 2.0.2

MICROSITE SURVEY - SAMPLE ASSORTMENTS AND COLLECTION METHODS

LIGHTNING RIDGE Collected by opal miner from one claim LOCAL over several years. Isolated blocky pieces, FIELDS 10-30 mm. (Collection at the Australian Museum, Sydney) 1 VERTICAL BILL’S 29o 27’ 19” S. 147o 58’ 02” E. First level - depth 14-15 m. 3 EASTERN FALL plant material, pine cones, ?lycopod plant – wood, pine cones, cone cores pelecypods and gastropods pelecypod bivalves - 2 taxa crayfish gastroliths viviparid snail – Albianopalin sp. ?elasmobranchid symphyseal fragment crayfish gastroliths very large fish tooth large fish jaw fragment plesiosaur tooth ?crocodile caudal centrum large theropod vertebral centrum dromaeosaurid tooth small carnosaur/megalosaur tooth theropod phalanx large mammal-like tooth – ?synapsid ?stapes of a large archosaur indeterminate bone fragments unidentified bone elements

Second level - depth 19 m. Collected by author, from old mullock on pine cones several claims. About 30 hours search gastropod snail time. 20-30 isolated specimens, many very large lungfish toothplate small fragments. Blocky shapes, 3-50 mm. indeterminate bone fragments (Collection at the Australian Museum, Sydney) 100+ specimens, collected by opal miners over about 5 years from two adjoining claims. Retrieved from both 4 LUNATIC HILL first and second levels, producing two Second level depth 18 m. groupings. Isolated robust elements, plant material - reeds, cones 15-50 mm. Quality variable. No turtles. crayfish gastroliths (Collection at the Australian Museum, pelecypods Sydney) viviparid – Albianopalin sp. theropod carpal or tarsal indeterminate bone fragments 2 MACNAMARA’S Depth 20 m. Collected by author. Material ‘specked’ pelecypod over many years from mullock on one crayfish gastrolith claim. Probably 25 hours of search. Fine lungfish branchiostegal preservation in small pieces; complex plesiosaur tooth shapes. 20-30 well defined isolated 2 teeth – Muttaburrasaurus sp. specimens, 3-20 mm. (Collection at the crocodile caudal centra Australian Museum, Sydney) indeterminate bone scraps

375 the Australian Opal Centre, Lightning Ridge)

5 HOLDEN’S GPS 29o.27.885 south, 147o 57.69 east FIELDS WEST AND NORTH plant detritus - pine cones, stems with leaf scars OF TOWNSHIP invertebrate trace fossil (worm tubes) 60 mussel shells, various taxa 7 THORLEY’S SIX MILE gastropods - Albianopalin sp. First level depth 13 m. - Melanoides sp. wood and plant fragments - pine cones, 150+ crayfish gastroliths twigs (?Lycopodium), leaf scales, seeds teleost fish dentary crayfish gastrolith Ceratodus wollastoni toothplate unidentified cranial element Neoceratodus forsteri toothplate indeterminate bone fragments ?Neoceratodus sp. toothplate fragment large ornithopod trackway - manus and multiple turtle elements, articulated foot print at 13 m depth in roof of mine ichthyosaur vertebra plesiosaur teeth x 4 Collected by author from surface mullock, Crocodylus selaslophensis – searched for about 8 hours over several 6 articulated thoracic and 7 articulated years. Exceptional preservation in minute caudal vertebrae items. 20 hours of searching under 10x hypsilophodontid jaw fragment with lens yielded many small specimens. germ tooth and other elements Thorley’s has been ‘rehabilitated’ so this theropod dinosaur elements source of microfossils no longer exists. unidentified vertebrate (?reptile) Complex shapes; 1-25 mm. Underground monotreme mammal thoracic vertebra ornithopod trackway recorded in photographs and traced outlines. Collection by opal miners from one (Collection at the Australian Museum, claim. Several hundred diverse Sydney) specimens. Fine preservation, including rare and important material. Articulated and isolated material, complex shapes. 5-- 8 SEVEN MILE -50 mm. (Collection at the Australian wood and plant material, pine cones Opal Centre, Lightning Ridge) crayfish gastroliths pelecypod bivalves gastropods - viviparid snail 6 SHALLOW FOUR MILE turtle – xiphiplastron ref. Spoochelys; plant detritus vertebrae invertebrate ichnofossil – worm casts crocodile caudal vertebra mussel shells (4 or 5 taxa) inc. indeterminate bone fragments Palaeohyridella sp., weathered bone scraps Collected by author from one large bucket of fossil debris (‘opal rough’) purchased Collection by author from old mullock. from opal miner. Preservation poor to very Palaeohyriids are rare outside Coocoran good. 10-20 specimens. Mostly blocky, fields. Fine preservation, mussels isolated items. 5-40 mm. (Collection at the no evidence of predepositional Australian Museum, Sydney) weathering. 11-30 mm. (Collection at

376 Collected by author from surface 9 TEN MILE mullock. Isolated blocky elements to 25 lungfish toothplate mm. (Collection at the Australian articulated turtle humerus and ulna ref. Museum, Sydney) Spoochelys articulated hypsilophodontid hindlimb - femur, tibia, astragalus ref. 12 OLD COOCORAN Fulgurotherium weathered and unworn plant debris, small sauropod tooth fruiting structures, cone cores, cones, drupes, catkins, Collected by opal miner. Small number seeds and pods – several kilos of important specimens including non-monotreme mammal element articulated material. Exquisite preservation, complex shapes. To 180 Collected by author from surface mm. (Collection at the Australian mullock, over many days. Atypical site Museum, Sydney) with abundant plant material and very rare bone elements. No molluscs or crayfish gastroliths. Preservation very precise, 10 WYOMING plant fossil includes diverse structures and plant material - pine stems, cones, nuts, delicate unworn items to 45 mm. seeds (Collection at the Australian Opal Centre, pelecypod - Palaeohyridella Lightning Ridge) viviparid snails crayfish gastroliths turtle elements 13 MUTTABUN PUDDLING DAM 3 plesiosaur teeth 29o 25’ 40” S 147o 45’ 15” E. small crocodile tooth plant detritus, pine twigs, cones, seeds ?theropod carpal and tiny caudal crayfish gastroliths indeterminate bone fragments very small turtle elements avian vertebral centrum Collected by author from tailing heap three avian tibiotarsus fragments and agitator fines representing 30-50 indeterminate bone fragments truckloads. Quality poor to excellent. Small turtle elements and articulation in Collected by author. Opal dirt originally three tiny plesiosaur teeth. Complex from Old Coocoran, processed by opal shapes. 3-35 mm. (Collection at the miners. Exceptionally fine preservation Australian Museum, Sydney) with internal microstructure. About 30-50 specimens, some evidence of articulation. Complex unworn shapes; 3-30mm. COOCORAN FIELDS (Collection at the Australian Museum, Sydney) 11 NEW COOCORAN FIELD wood, plant detritus, pine stems, cones ?polychaete or annelid worm tubes 14 MOLYNEUX’ crayfish gastrolith wood and plant detritus, cones gastropod snail – Melanoides sp. pelecypod bivalves small crocodile teeth crayfish gastroliths indeterminate bone fragments sauropod tooth indeterminate bone fragments

377 Collected by author from tailing heap and Collected by author from one mullock agitator fines from a single claim. About heap. 6 hours searching. 5-10 well 15 hours searching. 50+ well defined preserved isolated robust items. To 25 specimens. Quality poor to fine, with mm. (Collection at the Australian waterwear evident but excellent small Museum, Sydney) items. A good diversity and articulated material (e.g. three small carpals; five small caudal vertebrae). Complex forms. 15 DEAD BIRD To 35 mm. (Collection at the Australian wood fragments, twigs, seeds and cones, Museum, Sydney) Equisetum sp. fragments crayfish gastroliths pelecypod bivalves 17 DEAD BIRD turtle – scraps of carapace and vertebrae weathered plant detritus – several kilos sauropod tooth mussel shells small hypsilophodontid femur cf large teleost jaw fragment with alveoli Fulgurotherium Ceratodus sp. – unusually large toothplate small ?ornithopod basioccipital 3 plesiosaur teeth tiny dentary hypsilophodontid taxon 4 very large crocodile tooth base scrap theropod elements – articulated tarsals, crocodile vertebral centrum metatarsals, phalanges, unguals, multiple turtle elements - Spoochelys calcaneum and vertebrae hypsilophodontid dinosaur thoracic vertebrae, femur and other podial elements Opal miner’s collection from one claim, unidentified vertebrate (?reptile) elements over one year. Many excellent specimens. Fossils in discrete area of Collected by opal miners. Mostly eroded the claim. Evidence of articulation material, but interesting and rare elements. Complex shapes. To 45 mm. Evidence of articulation; mostly blocky (Collection at the Australian Museum, elements. To 55 mm. (Collection at Sydney) Australian Opal Centre, Lightning Ridge)

16 DEAD BIRD 18 SMITH’S wood, plant material, pine fragments, plant debris, cones cones, seeds pelecypod mollusc pelecypod bivalves dromaeosaurid tooth gastropods – Melanoides and pulmonate edentulous dentary of ornithorhynchid - snail monotreme taxon 3 crayfish gastroliths turtle elements ref. Spoochelys – Collected by author. Tailing heap from plastron, vertebrae, limb fragments, unknown number of truckloads. Many carpals and tarsals. hours searching! Monotreme dentary Opalania cervical rib beautifully preserved. Isolated robust plesiosaur tooth elements to 45 mm. (Collection at the crocodile caudal vertebrae fragments Australian Museum, Sydney) 2 sauropod teeth hypsilophodontid ungual dromaeosaurid tooth 19 EMU’S indeterminate bone fragments wood, plant material, pine cones Palaeohyridella and Hyridella sp. pulmonate snail

378 crayfish gastroliths about 35 mm. (Collection at the turtle elements – vertebrae, large centra, Australian Museum, Sydney) plastron/carapace and limb bones crocodile caudal vertebra plesiosaur teeth 22 EMU’S dromaeosaurid tooth wood and plant pieces sauropod tooth turtle vertebra and neural arch fragments indeterminate bone fragments small ornithopod pubis indeterminate bone fragments Collected by author from one tailing heap. Quality poor to excellent but Collected by author from tailing heap many pieces heavily eroded. Almost all from one claim; fossil material from potch from this site was fossiliferous. one or two truckloads. Preservation Evidence of articulated items in matrix. poor or partially silicified. Few items in Blocky material. To 45 mm. total; less than one hour searching. (Collection at the Australian Museum, Blocky isolated material to about 40 mm. Sydney) (Collection at the Australian Museum, Sydney)

20 EMU’S wood and plant material 23 EMU’S pelecypod bivalves - several taxa weathered plant debris, pine cones, gastropods - 2 taxa catkins, cone cores, seeds, pods and ?elasmobranchid or temnospondyl-like fruiting bodies bone or cartilage scraps ichnofossil - worm tube indeterminate bone fragments mussel shells Palaeohyridella sp. gastropods - Melanoides sp. Collected by author, 4 hours searching Albianopalin sp. (viviparid) from a tailing heap representing 5-8 crayfish gastroliths truckloads. Heavy weathering, quality small lungfish toothplate Neoceratodus generally poor. Many Palaeohyridella. forsteri Robust isolated elements to 45 mm. plesiosaur tooth (Collection at the Australian Museum, turtle ilium fragment Sydney) hypsilophodontid dinosaur vertebrae and podials theropod dinosaur caudal centra 21 EMU’S unidentified vertebrate (?reptile) elements wood, plant material, pine cones Palaeohyridella sp., larger unionoids Collected by opal miner from one claim. viviparid snails Isolated elements to 40 mm. Complex very large crayfish gastroliths shapes. (Collection at the Australian Opal teleost vertebra and jaw scraps Centre, Lightning Ridge) turtle centra indeterminate bone fragments 24 EMU’S FENCELINE Collected by author from tailing heap weathered plant material and plant representing many truckloads from one microfossil claim. Quality poor to average; some invertebrate trace fossil – worm tubes items very worn. 10 hours searching hyriid mussels produced about 15 well defined multiple turtle elements specimens. Blocky isolated elements to

379 2 plesiosaur teeth, one very large 26 KELLIE’S THREE/BENO’S specimen small pine cones twigs, stems, seeds, 50+ dinosaur elements, cone scales hypsilophodontid and theropod crayfish gastroliths including vertebrae, limb bones, small turtle costal and ungual phalanges, unguals ? tooth possible ?prosauropod tooth large sauropod ?rib 20 unidentified vertebrate (?reptile) elements Collected by opal miner and author ?coprolites from tailing heap from one claim. Very fine plant material with large variety of Collected by opal miners. Outstanding seeds and fruiting bodies. Complex assortment of articulated and unusual forms. 3-25 mm. (Collection at the dinosaur material. Complex shapes; to Australian Museum, Sydney and 55 mm. (Collection at the Australian Australian Opal Centre, Lightning Opal Centre, Lightning Ridge) Ridge)

25 ALLAH’S 27 KELLIE’S FOUR large quantities of plant material – pine waterworn wood fragments – 2+ kilos cones, Palaeohyridella godthelpi catkins, drupes, seeds, nuts, fruiting viviparid gastropods bodies turtle vertebra and plastron pelecypod bivalves crocodile caudal and vertebral centrum gastropods - viviparids dromaeosaurid tooth crayfish gastroliths Steropodon-like tooth fragment large teleost jaw and bone fragments indeterminate bone fragments lungfish toothplate pieces turtle tibia ref. Spoochelys; sacral and Collected by author after 4 hours caudal vertebrae and carapace searching through one tailing heap. fragments Preservation poor to good, some heavily 2 small crocodile teeth waterworn. About 20-30 good specimens. sauropod tooth Unusual plant forms - ridged stems, 2 dromaeosaurid teeth tetragonal in section; spearpoint shaped theropod carapals or tarsals and caudal pieces. Complex shapes to 30 mm. vertebra (Collection at the Australian Museum, small ornithopod lower cheek tooth cf Sydney) Atlascopcosaurus loadsi indeterminate bone fragments 28 KELLIE’S TWO / MOONSHINE Collected by author and opal miner from wood, plant material, stem fragments with one claim, from tailing heap. 50 leaf scar patterns, growing points, pine truckloads represented. Abundant fossil cones and catkins material in discrete areas of the opal pelecypod mussels - several taxa horizon. 30-40 good specimens. gastropods - Albianopalin sp and naticid Complex forms. 5-45 mm. (Collection at 2 teleost vertebrae the Australian Museum, Sydney and lungfish branchiostegal Australian Opal Centre, Lightning Ridge) 2 very large lungfish toothplates - Ceratodus wollastoni and Ceratodus sp. turtle vertebrae Sunflashemys; carapace scraps, femora

380 2 dromaeosaurid teeth crayfish gastrolith theropod pedal phalanx turtle carapace fragments, caudal hypsilophodontid femur - vertebrae ?Fulgurotherium sacral vertebra - Crocodylus Kollikodon ritchiei type AMF96602 selaslophensis indeterminate bone fragments small sauropod teeth undeterminate bone fragments Collected by opal miners from a small area of one claim at 15 m depth. Collected by author from tailing heap Abundant fossil,with fine internal representing 20 truckloads from one preservation. Evidence of articulation in mineral claim. Many small items and turtle vertebrae and an interesting microfossils lost in the wash. Blocky assortment of excellent plant specimens. forms to 35 mm. (Collection at the Type site for Kollikodon ritchiei. About Australian Museum, Sydney) 40 beautifully preserved specimens. Delicate complex shapes; 5-35 mm. (Collection at the Australian Museum, 31 KELLIE’S ONE Sydney) wood and plant material, plant litter, seeds, leaf scales, pine cones crayfish gastroliths 29 KELLIE’S TWO / MOONSHINE teleost fragments - skull element, teeth, miscellaneous weathered plant debris, otolith, vertebral centra stem fragments with leaf scars 10 – 15 ganoine fish scales cf Richmondichthyes kilos lungfish toothplate - Neoceratodus forsteri ichnofossil worm tube turtle - Spoochelys - multiple carapace pelecypod mussels Palaeohyridella sp. and plastron fragments and tiny elements. and others tiny ?reptile jaw fragment gastropods - Albianopalin sp. 5 plesiosaur teeth - Melanoides sp. crocodile - scute with circular pits, 8 small - undetermined naticid crocodile teeth crayfish gastroliths pterosaur limb bone shaft teleost fragment tiny unidentified reptile elements - femur lungfish toothplate and cartilage scraps or humerus, caudal vertebra, carpal turtle elements Sunflashemys phalanx (?embryonic dinosaur); teeth; 2 plesiosaur teeth neural arch hypsilophodontid vertebral centrum small complete ?theropod toebone indeterminate bone fragments tiny ?hypsilophodontid tooth small crushed hypsilophodontid femur Collected by opal miners from mineral unidentified vertebrate elements claim adjoining type location of Kollikodon ritchiei. Eroded material Collected by opal miner and Henk with a few precise specimens. To 80 Godthelp of University of New South mm. (Collection at the Australian Opal Wales. Many unique specimens in fine Centre, Lightning Ridge) condition, representing small vertebrates. Very few molluscs. Fish teeth, turtle shell, unusual ?reptile elements, very small 30 KELLIE’S ONE dinosaur tooth and femur of particular plant material, pine cones, fruit or nut-like interest. Semi-articulated turtle material. forms Assortment diverse, representing a death pelecypod mussels - 2 or 3 taxa assemblage from a small area. Delicate, viviparids - Albianopalin sp.

381 complex forms from 3-45 mm. (Collection hundreds of mussel shells, variably at the Australian Museum, Sydney) preserved as steinkerns or fully opalised; mostly articulated with valves closed. Blocky forms to 45 mm. (Collection at 32 KELLIE’S ONE the Australian Museum, Sydney and charophytes Australian Opal Centre, Lightning plant debris, microfossil and mats, Ridge) pinecones, stems with growing points and gall structures 34 TYRONE’S / SMITH’S 6 teleost denticles, rib, vertebrae, skull First level at 13 m. fragments ?Lycopodium sp. fragments one freshwater mussel- Palaeohyridella pelecypod mollusc Richmondichthyes sp. ganoine scales small crayfish gastrolith frog (Anura) maxilla with teeth turtle - Sunflashemys bartondrackettii type snake (Squamata) dentary with teeth AMF116217 turtle elements - Spoochelys crocodile scute fragments Second level at 26 m. dinosaur vertebral centrum, tooth base turtle caudal vertebra – ref. Spoochelys ornithomimosaurid vertebra - ?Timimus monotreme sacral vertebra unidentified theropod neural arch dromaeosaurid ungual fragment Material from first level collected by opal unidentified ?fibula and other bone miner and author; Sunflashemys type fragments location. Complex delicate shapes to 60 mm. (Collection at the Australian Collected by Henk Godthelp from Museum, Sydney) topdirt and underground. Diverse collection with microfraction. Important records (charophytes, anuran, squamate, 35 T-BONE EXTENSION ornithomimosaurid, dromaeosaurid). plant material - seeds, leaf scales, cones, Microfossils and delicate structures to catkins, drupes; horsetail fragments around 45 mm. (Collection at the (Equisetum sp.) Australian Opal Centre, crayfish gastroliths Lightning Ridge) pelecypod mussels (several taxa) pulmonate gastropod small teleost jaw with tooth bases 33 SOUTHERN OLGA’S toothplate – juvenile Ceratodus wollastoni weathered plant material turtle material - 150+ pieces of skull, pine cones and catkins shell, vertebrae, podials – Spoochelys, unusual large flattened seed pods, stem Opalania sections plesiosaur tooth several hundred mussel shells – crocodile teeth Palaeohyridella sp., Protovirgus sp. and sauropod tooth other unidentified taxa hypsilophodontid femur proximal teleost fish vertebra unidentified ?dinosaur vertebral centra large plesiosaur tooth small ?prosauropod tooth turtle plastron scrap theropod caudal centra, carpal and tarsal sauropod tooth phalanges indeterminate bone elements Collected by author and opal miner. Unusual, low diversity assemblage, with Collected by opal miners from one claim

382 Over two years. Specimens retrieved Collected by author from tailing heap. direct from underground and from Blocky isolated pieces to 18 mm. tailings after processing. Assortment (Collection at the Australian Museum, includes microfossils, semi-articulated Sydney) turtle material (Opalania, Spoochelys), hypsilophodontid and theropod material. Complex delicate forms to 50 mm. 39 STEEN’S RUSH / COOCORAN B (Collection at the Australian plant detritus - small quantity Museum,Sydney and the Australian pelecypod mussels Opal Centre, Lightning Ridge.) two plesiosaur teeth turtle material, many elements

36 T-BONE EXTENSION Collected by opal miners. Well plant material preserved, articulated turtle material, crayfish gastroliths badly damaged by mining machinery; turtle elements x 10 – peripherals, under study. Mostly blocky elements to vertebrae about 30 mm. (Collection at the plesiosaur teeth Australian Opal Centre, Lightning Ridge). dinosaur vertebral centra unidentified vertebrate elements coprolite 40 POTATO PATCH / RAINBOW ?monotreme tibia plant detritus, pine cones, fruiting structures Small collection by opal miner, from bark sections with invertebrate trace mineral claim within 100 m of site 35. ichnofossil (?worm tube) Part of large palaeochannel assemblage. hyriid mussels - Palaeohyridella sp. Mostly robust elements but evidence of crayfish gastroliths articulated and associated material. teleost jaw fragment with alveoli (Collection at the Australian Opal plesiosaur tooth scrap Centre,Lightning Ridge) crocodile podial fragment tibia of large hypsilophodontid unidentified vertebrate (?reptile) elements 37 MOLYNEUX’ EAST plant detritus, pine cone Collected by opal miners from one site. Albianopalin benkeari and limnaeid Small robust isolated elements with one gastropods large unweathered hypsilophodontid tibia crayfish gastrolith to 200 mm. (Collection at the Australian turtle humerus fragment Opal Centre, Lightning Ridge) sauropod tooth

Collected by author from one mullock heap. Blocky pieces to 25 mm. (Collection at the Australian Museum Sydney)

38 CC’S turtle coracoid small monotreme dentary fragment - taxon 5

383

APPENDIX 3.0

THE LIGHTNING RIDGE LOCAL FAUNA APPENDIX 3.0

THE LIGHTNING RIDGE LOCAL FAUNA

Locality: Opal fields at Lightning Ridge, New South Wales Approx 29.5oS 148oE Rock unit and age: Finch Claystone Facies of the Wallangulla Sandstone Member of the Griman Creek Formation. Middle Albian (100 million years) on palynological evidence (Morgan 1984).

Chlorophyceae Charophyta undetermined taxon

Foraminifera Hyperammina sp Ramulina tetrahedralis ?radiolarian

Polychaeta undetermined taxon

Mollusca Pelecypoda Alaythyria jaqueti Newton 1915 Megalovirgus wintonensis Hocknull 1997 Hyridella macmichaeli Hocknull 1997 Hyridella (Protohyridella) goondiwindiensis Hocknull 1997 Palaeohyridella godthelpi Hocknull 2000 Coocrania hamiltonbrucei Kear 2006 ~5 undetermined taxa large ?hyriid (LRF798) sphaeriid (LRF1154, LRF1156, LRF1169) ‘tellen’ or nut shell (LRF16, LRF1429)

386 corbiculid ‘river pea shell’ (LRF17) strongly ridged subcircular unionoid (pers. obs.)

Gastropoda Viviparidae Albianopalin benkeari Hamilton-Bruce et al. 2002 Albianopalin lizsmithae Hamilton-Bruce et al. 2002 Notopala sp. Hamilton-Bruce et al. 2002 Melanoides godthelpi Hamilton-Bruce et al. 2004 Fretacaeles gautae Hamilton-Bruce and Kear 2006 thiarid taxon 2 (LRF544) undescribed succineid (under study) undescribed naticid (pers. obs.)

Crustacea - Decapoda freshwater crayfish – undetermined taxon

Pisces small shark cf Isurus or Cretolamna Actinopterygia Teleostei ~ 4 undetermined taxa (Susan Turner pers. comm.) aspidorhynchid cf Richmondichthys sweeti Etheridge et al. 1891 Anguilliforme freshwater eel – undetermined taxon (Tom Rich pers. comm.) Dipnoi – lungfish Ceratodontidae Ceratodus wollastoni Chapman 1914 (Kemp and Molnar 1981) Ceratodus sp. (Kemp 1991) Neoceratodontidae Neoceratodus forsteri Krefft 1870 (Kemp and Molnar 1981)

387 Anura frog – undetermined taxon (Henk Godthelp pers. comm.)

Ichthyopterygia – Ichthyosauria ichthyosaur - undetermined taxon (Ben Kear pers. comm.; pers. obs.)

Sauropterygia Pliosauria ?Leptocleidid pliosaur (Kear 2006)

Testudines Superfamily Meiolanoidea Spoochelyidae n. fam. Spoochelys ormondea n. gen., n. sp. Sunflashemys bartondrackettii n. gen., n. sp. Opalania baagiiwyamba n. gen., n. sp. Pleurodira Chelidae indet. ~2 taxa Testudines indet. ~2 taxa

Lepidosauria – Squamata snake – undetermined taxon (Henk Godthelp pers. comm.)

Crocodylia Crocodylus (?Botosaurus) selaslophensis Etheridge 1917 ziphodont crocodile – undetermined taxon (Molnar and Willis 2001) ‘round tooth’ morphotype – undetermined taxon (Molnar and Willis 2001; pers. obs.)

Pterosauria pterosaur - undetermined taxon (Henk Godthelp pers. comm.; pers. obs.)

388 Dinosauria Ornithischia stegosaurid (Dr Ben Kear pers. comm.; pers. obs.) Ornithopoda Muttaburrasauridae Muttaburrasaurus sp. (Molnar 1991, 1996) Hypsilophodontidae Fulgurotherium australe von Huene 1932 (Molnar and Galton 1980) Atlascopcosaurus loadsi Rich and Rich 1989 ~ 4 undetermined taxa (pers. obs.) Saurischia Sauropodamorpha Prosauropoda (pers. obs.; LRF660) Sauropoda Titanosauriformes - peg tooth morphotype 1 (pers. obs.) - spatulate tooth morphotype 2 (LRF10; pers. obs.) - acuminate tooth morphotype 3 (LRF461) Theropoda Rapator ornitholestoides von Huene 1932 Theropoda incertae sedis Ceratosauridae undetermined ?abelisaurid (LRF100 – LRF103) Dromaeosauridae undetermined dromaeosaurid (LRF326) Ornithomimosauridae ?Timimus sp. (LRF543; Henk Godthelp pers. comm.) Spinosauridae undetermined ?spinosaurid (Ben Kear pers. comm.; pers. obs.)

Aves undetermined ornithoracines - two taxa (Molnar 1999) undetermined taxon cf Hesperornis (LRF443; Henk Godthelp pers. comm.)

389 Mammalia Synapsida undetermined ?synapsid (AMF118621; Clemens et al. 2003) Monotremata Steropodontidae Steropodon galmani Archer et al 1985 undetermined ornithorhynchid taxon 3 (Henk Godthelp persn. comm..) undetermined taxon 4 (AMF97263; pers. obs.) undetermined small form, taxon 5 (pers. obs.) Kollikodontidae Kollikodon ritchiei Flannery et al 1995 Undetermined small non-monotreme mammal (pers. obs.)

390