Investigations Into the Evolution of Australian Mammals with a Focus on Monotremata
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INVESTIGATIONS INTO THE EVOLUTION OF AUSTRALIAN MAMMALS WITH A FOCUS ON MONOTREMATA Thesis submitted by ANNE MARIE MUSSER August 2005 For the Degree of Doctor of Philosophy in the School of Biological, Earth & Environmental Sciences University of New South Wales ABSTRACT This thesis began as an investigation into evolution of the platypus family (Ornithorhynchidae, Monotremata), now known from both Australia and South America. The thesis broadened its scope with inclusion of non-ornithorhynchid Mesozoic monotremes from Lightning Ridge, NSW. This change in direction brought an unexpected result: a fossil mammal from Lightning Ridge investigated for this thesis (presumed to be monotreme: Flannery et al., 1995) appears to be a new and unique type of mammal. Specimens were procured through Queensland Museum (Riversleigh material); Australian Museum (Lightning Ridge material); and Museum of Victoria and the South Australian Museum (fossil ornithorhynchids). Specimens were examined under a light microscope and scanning electron microscope; specimens were photographed using light photography and a scanning electron microscope; and illustrations and reconstructions were done with a camera lucida microscope attachment and photographic references. Parsimony analysis utilised the computer programs PAUP and MacClade. Major conclusions: 1) analysis and reconstruction of the skull of the Miocene platypus Obdurodon dicksoni suggest this robust, large-billed platypus was a derived northern offshoot off the main line of ornithorhynchid evolution; 2) the well-preserved skull of Obdurodon dicksoni shows aspects of soft anatomy previously unknown for fossil ornithorhynchids; 3) two upper molars from Mammalon Hill (Etadunna Formation, late Oligocene, central Australia) represent a third species of Obdurodon; 4) the South American ornithorhynchid Monotrematum sudamericanum from the Paleocene of Argentina is very close in form to the Oligocene-Miocene Obdurodon species from Australia and should be considered congeneric; 5) a revised diagnosis of the lower jaw of the Early Cretaceous monotreme Steropodon galmani includes the presence of two previously undescribed archaic features: the probable presence of postdentary bones and a meckelian groove; 6) morphological evidence is presented supporting a separate family Steropodontidae; and 7) analysis of new fossil material for Kollikodon ritchiei suggests that this taxon is not a monotreme mammal as originally identified but is a basal mammal with close relationships to allotherian mammals (Morganucodonta; Haramiyida). Kollikodon is provisionally placed as basal allotherian mammal (Allotheria sensu Butler 2000) and is unique at the ordinal level, being neither haramiyid nor multituberculate. A new allotherian order – Kollikodonta – is proposed. i ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project’s design and conception or in style, presentation and linguistic expression is acknowledged.’ Anne Marie Musser 31 August 2005 ii TABLE OF CONTENTS Abstract i Originality Statement ii Table of Contents iii List of Figures viii List of Tables x Acknowledgments xi Introduction to the thesis 1 Mammalian evolution in the southern hemisphere 2 Australia’s role: a key player 3 General aims and approach of this thesis 4 Chapter aims and results 5 References 7 CHAPTER 1: A review of the monotreme fossil record and 14 comparison of palaeontological and molecular data. Abstract 16 Introduction 16 Early mammalian evolution 17 Mesozoic mammals from the southern hemisphere 20 Mesozoic monotremes 21 Cainozoic monotremes 22 The relationship between platypus and echidnas 23 ‘Molecules vs. morphology’: consensus or disagreement? 24 Prototherian-therian dichotomy 24 The Marsupionta hypothesis 25 iii A trichotomy 27 Future directions 28 Summary 28 Acknowledgements 29 References 29 CHAPTER 2: Furry egg-layers: monotreme relationships and radiations 33 Introduction 35 Living monotremes 36 Echidnas 37 Monotreme morphology 39 Skull structure 41 Postcranial skeleton 44 Soft anatomy and physiology 46 Fossil monotremes 48 Cretaceous forms 48 Ornithorhynchids 52 Fossil tachyglossids 58 Biogeography 63 Monotreme relationships 65 Relationships within Monotremata 65 Relationships with other mammals 66 Gondwanan radiation 67 Evolutionary trends 67 Summary 68 Acknowledgements 68 References 68 CHAPTER 3: New information about the skull and dentary 74 of the Miocene platypus Obdurodon dicksoni and a discussion of ornithorhynchid relationships Introduction 76 Materials and methods 77 iv Referred specimens 77 Abbreviations 77 Results 77 Dorsal view 79 Ventral view 81 Lateral view 82 Foramina 83 Discussion of the differences in cranial morphology separating 87 Ob. dicksoni from Or. anatinus Development of the bill in ornithorhynchids 88 Comparisons involving the crania and dentaries Dental evolution in ornithorhynchids 89 Relationships within Monotremata 90 Relationships within Ornithorhynchidae Addendum 90 References 90 CHAPTER 4: Evolution, biogeography and palaeoecology 93 of the Ornithorhynchidae Abstract 96 Fossils and evolutionary relationships 96 Morphology 99 Dental morphology 100 Cranial morphology 100 Postcranial morphology 102 Biogeography, distribution and palaeoecology 103 Factors limiting distribution of ornithorhynchids 107 A conservation message 107 Acknowledgements 108 References 108 CHAPTER 5: Kollikodon ritchiei: Description, relationships and 112 reassessment of affinities v Abstract 114 Introduction 115 Geological and palaeontological setting 115 Opalisation: processes, timing and preservation of fossils 118 Associated flora and fauna 119 Materials and methods 121 Description 122 Maxilla 122 Palatine 126 Lower jaw 128 Upper dentition 132 Lower dentition 137 Occlusion and dental function 139 Comparisons and discussion 140 Tritylodontoidea 140 Morganucodonta 145 Docodonta 148 Haramiyida 151 Multituberculata 153 Monotremata 157 Other Gondwanan Mesozoic mammals 159 Phylogenetic analysis 160 Data sets and character coding 160 Results 167 General discussion 169 Summary of morphology and function 167 Relationship hypotheses 175 A model for derivation of molar form 181 vi ‘Prototheria’ revisited 183 Conclusions 184 Taxonomic relationships 186 Future directions 187 Acknowledgements 187 Literature cited 188 Appendices 206 Thesis Conclusions 228 References 240 Appendices -1- vii LIST OF FIGURES CHAPTER 1 Figure 1: The geological timescale and the monotreme fossil record 19 CHAPTER 2 Figure 1: The eastern New Guinea long-beaked echidna Zaglossus bartoni 38 Figure 2: The skull and dentary of the living platypus 40 Ornithorhynchus anatinus Figure 3: Skull and dentary of the Short-beaked Echidna 43 Tachyglossus aculeatus Figure 4: The skeleton of the Short-beaked Echidna 45 Tachyglossus aculeatus Figure 5: Shoulder girdle of the Short-beaked Echidna 46 Tachyglossus aculeatus Figure 6: Steropodon galmani: right dentary fragment with M/1-M/3 49 in place and an alveolus for the last premolar (anterior is to the right) Figure 7: Kollikodon ritchiei, right maxillary fragment and right 50 dentary fragment Figure 8: Teinolophos trusleri: comparison between the penultimate molar 51 of T. trusleri and the M/2 of S. galmani Figure 9: Molar teeth of Steropodon galmani and Ornithorhynchidae 52 Figure 10: Reconstruction of the skull and dentary of 57 the Miocene platypus Obdurodon dicksoni Figure 11: Skulls of fossil Australian long-beaked echidnas 59 Figure 12: A restoration of the giant Western Australian echidna 61 'Zaglossus' hacketti Figure 13: Map of Australia showing the present and historic distribution 64 of ornithorhynchids plus S. galmani CHAPTER 3 viii Figure 1: Reconstruction of the skull and dentary of Obdurodon dicksoni 78 Figure 2: The skull and dentary of Ornithorhynchus anatinus 80 CHAPTER 4 Figure 1: Left lower first molar, holotype of Obdurodon insignis (SAM P18087), 97 illustrating the blade structures of ornithorhynchid molars Figure 2: Comparison of the bill and marginal cartilage between 101 Obdurodon dicksoni and Ornithorhynchus anatinus Figure 3: Map of ornithorhynchid distribution 105 CHAPTER 5 Figure 1: Position of Lightning Ridge in Early Cretaceous 116 Figure 2: Extent of incursion of Eromanga Sea 117 Figure 3: Occlusal view, maxilla and dentary 124 Figure 4: Lateral view, maxilla and dentary 125 Figure 5: Medial view, maxilla and dentary 127 Figure 6: Posterior view of maxilla 128 Figure 7: Details of palatal region 129 Figure 8: Posterior views of dentaries of K. ritchiei and Steropodon galmani 131 Figure 9: SEMs of apical pits on molar cusps 135 Figure 10: Upper and lower teeth in occlusion 139 Figure 11: Cladogram of phylogenetic relationships 168 Figure 12: Hypothesis for derivation of multicuspid teeth in Kollikodon 182 Figure 13: Comparisons between molar teeth of various taxa 179 ix LIST OF TABLES CHAPTER 1 Table 1: A glossary of terms highlighted in boldface in the text, 18 taken from