The first fossil sea turtles (Testudines: Cheloniidae) from the Cenozoic of Australia ERICH M. G. FITZGERALD and LESLEY KOOL FITZGERALD, E.M.G. & KOOL, L., XX.XX.2015. The first fossil sea turtles (Testudines: Cheloniidae) from the Cenozoic of Australia. Alcheringa 39, xxx–xxx. ISSN 0311-5518 An isolated dentary and costal identified as cf. Pacifichelys and Cheloniidae indet., respectively, are described from the upper Miocene–lower Plio- cene Black Rock Sandstone of Beaumaris, Victoria, Australia. These remains represent the first fossil evidence of sea turtles from the Cenozoic of Australia. Neither of the fossils can be referred to living genera, indicating that extinct cheloniids occurred in southeast Australian coastal waters for at least part of the late Neogene. Thus, the taxonomic composition of the current sea turtle fauna of Australia was apparently established within the last five to six million years. Erich M. G. Fitzgerald [efi[email protected]] and Lesley Kool [[email protected]], Geosciences, Museum Victoria, GPO Box 666, Melbourne, Victoria, 3001, Australia. Received 26.6.2014; revised 9.8.2014; accepted 14.8.2014. Key words: Pacifichelys, Neogene, Miocene, Pliocene, Victoria, marine, vertebrate. AUSTRALIAN seas are inhabited by six of the seven liv- 2012), sirenians (Fitzgerald et al. 2013), phocid seals ing sea turtle species of the families Cheloniidae and (Fordyce & Flannery 1983), baleen whales (Fitzgerald Dermochelyidae, including one endemic species 2004, 2012), odontocetes (Chapman 1912, 1917) and (Márquez 1990). Cretaceous marine basins of northern rare remains of terrestrial dromornithid birds (Park & Australia have additionally produced an abundance of sea Fitzgerald 2012b) and marsupials (Piper et al. 2006). turtle fossils, including the extinct genera Notochelone, To this rich local fauna we now add cheloniid turtles, Cratochelone, Bouliachelys and other indeterminate which constitute the first fossil evidence of sea turtles forms (Kear 2003, Kear & Lee 2006). Yet, a nearly from the Cenozoic of Australia. 66-million-year gap in the Australian sea turtle record separates an upper Maastrichtian fossil from Western Australia (Kear & Siverson 2010) and the Holocene Materials and methods diversity of sea turtles. Despite reports of alleged ‘turtle Institutional Abbreviations. LACM: Natural History bones’ from the marine lower Pliocene Grange Burn Museum of Los Angeles County, Los Angeles, USA. Formation of Victoria (Chapman 1914, p. 47), Australia NMV D: Museum Victoria Reptiles and Amphibians Downloaded by [Monash University Library] at 16:56 18 October 2014 has remained the only continental mainland without sub- Collection, Melbourne, Australia. NMV P: Museum stantiated Cenozoic fossil sea turtles. Proximal to the Victoria Palaeontology Collection, Melbourne, Australia. Australian mainland, fossil sea turtles have been described from the Quaternary of New Guinea (Vis Comparative Material. Dermochelyidae (Dermochelys 1905), and the Paleocene (Fordyce 1979, Buchanan et al. coriacea): NMV D54542, D57420 and D74912. Chelo- 2007), Eocene (Fordyce 1979, Köhler 1995, Karl & niidae (Chelonia mydas): NMV D5828, D58526 and Tichy 2007, Grant-Mackie et al. 2011) and Miocene D74919. Cheloniidae (Caretta caretta): NMV D54543, (Buckeridge 1981) of New Zealand. D65879 and D74935. Cranial osteological terminology – The shallow marine upper Miocene lower Pliocene follows Gaffney (1979). Black Rock Sandstone of Beaumaris, Victoria (southeast Australia; Fig. 1), has produced the Beaumaris Local Fauna, including sharks and rays (Kemp 1991), Geological setting fi osteichthyan sh (Chapman & Pritchard 1907), The coastal section at Beaumaris occurs onshore in the penguins (Park & Fitzgerald 2012a), diomedeid and cliffs, shore platform and beach shingle from pelagornithid seabirds (Wilkinson 1969, Fitzgerald et al. Table Rock about 1.6 km northeast to ‘Dog Tooth Rock’ (approximately opposite the intersection of Beach Road and Cliff Grove), and approximately 100 m out to © 2014 Museum Victoria http://dx.doi.org/10.1080/03115518.2015.964047 sea as submarine outcrop (Gill 1957). The rock is 2 ERICH M. G. FITZGERALD AND LESLEY KOOL ALCHERINGA 144° 148° ferruginous sandstone containing burrows but no carbonate (Abele et al. 1988, Wallace et al. 2005). The urr M ay Rive r 36° Beaumaris section of the Black Rock Sandstone repre- Australia Victoria sents a shallow marine sandy lower shoreface facies 27° (Wallace et al. 2005). The basal nodule bed and overlying 6.7 m of the area shown below Bass Strait Black Rock Sandstone at Beaumaris constitute the type area shown at right 40° 0 1000 km 0 100 km section of the Cheltenhamian southeast Australian mar- Tasmania ine stage, which was originally correlated with the N 145°06´ upper Miocene (Singleton 1941). More recently, the Melbourne microfossil assemblage from the Black Rock Sandstone at Beaumaris has indicated its deposition during plank- tonic foraminiferal zones N17b–N18 (Mallett 1977), Beaumaris late Messinian–early Zanclean, or about 4.5–6.5 Ma (McGowran et al. 2004, Hilgen et al. 2012). 87Sr/86Sr 38°03´ Beaumaris Bay 38°03´ dates from the basal nodule bed and overlying 5 m of Black Rock Sandstone at Beaumaris range between 6.2 Port Phillip Ma (within basal nodule bed) to 4.9 Ma (at 4.3 m high; Bay Dickinson et al. 2002, Wallace et al. 2005, Dickinson & Wallace 2009). These data indicate that the fossilifer- ous Black Rock Sandstone at Beaumaris was deposited between the latest Miocene and earliest Pliocene. Bass Strait The cheloniid fossils described here (NMV P240713, NMV P232865) were collected as float in the 0 10 km 145°06´ intertidal zone at Beaumaris; however their stratigraphic Fig. 1. Locality of Beaumaris in Victoria, southeastern Australia. provenance is not in doubt. Fine-grained, yellow, calcar- eous sandy matrix was found adhering to the fossils: exposed parallel (W–E) to the shoreline by a shallow this, and the relatively fine preservation of the bones asymmetrical anticline with its axis occurring at approx- themselves, suggests that the fossils were derived from imately the level (horizontally) of the intersection of the lower 6.7 m of the Black Rock Sandstone overlying Beach Road and Banksia Avenue (near 37°59ʹS, the basal nodule bed. Dickinson & Wallace (2009) 145°02ʹE; Gill 1957). From here, the strata dip eastward reported a spread of 87Sr/86Sr dates between 4.9 and 6.0 along strike at a shallow angle of ≤2° (Gill 1957). The Ma from this part of the section at Beaumaris. cliffs along the shoreline are parallel with the eroded Beaumaris Monocline, which has a seaward (SE) aver- Systematic palaeontology age dip angle of 10–20° (Gill 1957, Kenley 1967). The base of the sequence at Beaumaris consists of Class REPTILIA Laurenti, 1768 middle Miocene Fyansford Formation, which is discon- Order TESTUDINES Batsch, 1788 formably overlain by a thin (ca 20 cm thick) phosphatic Suborder CRYPTODIRA Cope, 1868 nodule bed at the base of the Black Rock Sandstone, Superfamily CHELONIOIDEA Baur, 1893 Downloaded by [Monash University Library] at 16:56 18 October 2014 which has a maximum thickness of about 15 m (Kenley Family CHELONIIDAE Oppel, 1811 1967, Abele et al. 1988). The clayey limestone of the Pacifichelys Fyansford Formation is not exposed in onshore outcrop, cf. Parham & Pyenson, 2010 and only in limited areas on the sea bed close to shore where it is covered by beach sand (Gill 1957). The Material. NMV P240713, nearly complete left dentary, phosphatic nodule bed at the base of the Black Rock collected by Timothy Flannery ca January 1982 – Sandstone consists of phosphatic and limonitic intra- (Figs 2 3). clasts and mollusc shells, together with resistant and usually isolated and abraded vertebrate elements (e.g., Locality. Found as float below high tide level on the teeth, vertebrae, ribs, cetacean ear bones) within a western shore of Beaumaris Bay at Beaumaris, north- quartz-rich sandy matrix (Singleton 1941, Gill 1957, east side of Port Phillip Bay, central coastal Victoria, Wallace et al. 2005). The nodule bed is only exposed at southeast Australia, near 37°59ʹ34ʺS, 145°02ʹ32ʺE. low tide. The succeeding ca 6.7 metres of Black Rock – Sandstone consists of fossiliferous fine calcareous sands Stratigraphic unit. Upper Miocene lower Pliocene and silts, commonly burrowed and containing mollusc- Black Rock Sandstone. and echinoid- (especially Lovenia) rich layers (Gill 1957, Abele et al. 1988). The top 8.5 m of the Black Description. The dentary is nearly complete, relatively Rock Sandstone comprises sparsely fossiliferous broad and dorsoventrally flattened (Fig. 2A, C). The ALCHERINGA CENOZOIC SEA TURTLES FROM AUSTRALIA 3 Fig. 2. cf. Pacifichelys, NMV P240713, isolated left dentary in: A, dorsal; B, ventral; C, lateral; and D, medial views. Specimen whitened with ammonium chloride. symphyseal length (20.0 mm) is 50.7% of the preserved of the dentary is smoothly rounded in the transverse dentary length (39.4 mm), similar in size to the juvenile plane. mandibles of Pacifichelys urbinai (Parham & Pyenson 2010, fig. 7). The triturating surface is expanded and flat to slightly concave transversely, with no accessory Comparisons. NMV P240713 compares most closely to fi ridge; its posterior edge is at a level just anterior to the the dentaries of Paci chelys urbinai Parham & position of the foramen dentofaciale majus. The broad Pyenson, 2010 and P. hutchisoni Lynch & Parham, and flattened triturating surface suggests specialization 2003 by having the following combination of fi fl for