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The Anatomy and Phylogenetic Relationships of Antetonitrus Ingenipes (Sauropodiformes, Dinosauria): Implications for the Origins of Sauropoda

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The Anatomy and Phylogenetic Relationships of Antetonitrus Ingenipes (Sauropodiformes, Dinosauria): Implications for the Origins of Sauropoda THE ANATOMY AND PHYLOGENETIC RELATIONSHIPS OF ANTETONITRUS INGENIPES (SAUROPODIFORMES, DINOSAURIA): IMPLICATIONS FOR THE ORIGINS OF SAUROPODA Blair McPhee A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013 i ii ABSTRACT A thorough description and cladistic analysis of the Antetonitrus ingenipes type material sheds further light on the stepwise acquisition of sauropodan traits just prior to the Triassic/Jurassic boundary. Although the forelimb of Antetonitrus and other closely related sauropododomorph taxa retains the plesiomorphic morphology typical of a mobile grasping structure, the changes in the weight-bearing dynamics of both the musculature and the architecture of the hindlimb document the progressive shift towards a sauropodan form of graviportal locomotion. Nonetheless, the presence of hypertrophied muscle attachment sites in Antetonitrus suggests the retention of an intermediary form of facultative bipedality. The term Sauropodiformes is adopted here and given a novel definition intended to capture those transitional sauropodomorph taxa occupying a contiguous position on the pectinate line towards Sauropoda. The early record of sauropod diversification and evolution is re- examined in light of the paraphyletic consensus that has emerged regarding the ‘Prosauropoda’ in recent years. iii ACKNOWLEDGEMENTS First, I would like to express sincere gratitude to Adam Yates for providing me with the opportunity to do ‘real’ palaeontology, and also for gladly sharing his considerable knowledge on sauropodomorph osteology and phylogenetics. This project would not have been possible without the continued (and continual) support (both emotionally and financially) of my parents, Alf and Glenda McPhee – Thank you. Natasha Phillips – thank you for your endless support and intellectual patience on all things dinosaur. In letting me pretend that I knew anything about the archaeological and human paleontological record and then paying me to both teach and record it, I would like to thank Kathleen Kumin. Bruce Rubidge I would like to thank for both his good humour and for assisting in trips to collections and conferences beyond Johannesburg. Bernard Zipfel, for responding to my constant requests for the collection keys with happy acquiescence, thank you. To both Jonah Choiniere and Jay Nair, thanks for giving me something more to think about after every conversation. To the Mike, Aurore, Vincent and Matt’s of the world – cheers for being a mate. Finally, I would like to thank my supervisor Fernando Abdala, for your prodigious patience, cladistic moxie, willingness to help, and providing me with (free) accommodation in Argentina. You are, like, probably, one of the sincerest human beings that I will ever meet. Chur. iv CONTENTS DECLARATION …………………………………………………………………………………………………………………….ii ABSTRACT……………………………………………………………………………………………………………………………iii ACKNOWLEDGEMENTS……………………………………………………………………………………………………….iv LIST OF FIGURES………………………………………………………………………………………………………………….vi LIST OF TABLES……………………………………………………………………………………………………………………vii 1. INTRODUCTION AND LITERATURE REVIEW ...................................................... 1 1.1 General Introduction .............................................................................................. 1 1.2 The Elliot Formation of South Africa ....................................................................... 3 1.2.1 Sauropodomorpha and the Lower Elliot Formation ................................................... 6 1.2.2 Internationally contemporaneous taxa and deposits ............................................... 11 1.3 Recent interpretations of sauropodomorph phylogenetics and the definition of Sauropoda ...................................................................................................................... 13 1.4 The Fossil Evidence: character-state dichotomies and the sauropodomorph/sauropod transition. .......................................................................... 17 2. METHODS AND MATERIALS .............................................................................. 29 3. RESULTS ................................................................................................................ 32 3.1 SYSTEMATIC PALEONTOLOGY ............................................................................... 32 4. ANATOMICAL DESCRIPTIONS ............................................................................ 37 4.1 Axial skeleton....................................................................................................... 37 4.1.1 Cervical vertebrae ..................................................................................................... 37 4.1.2 Dorsal vertebrae ........................................................................................................ 39 4.1.3 ?Caudosacral/anterior caudal ................................................................................... 48 4.1.4 Caudal vertebrae ....................................................................................................... 51 4.1.5 Chevrons and ribs ...................................................................................................... 54 4.2 Appendicular skeleton .......................................................................................... 55 4.2.1 Scapula ...................................................................................................................... 55 v 4.2.2 Humerus .................................................................................................................... 58 4.2.3 Ulna ........................................................................................................................... 62 4.2.4 Radius ........................................................................................................................ 65 4.2.5 Manus ........................................................................................................................ 67 4.2.6 Ilium ........................................................................................................................... 74 4.2.7 Pubis .......................................................................................................................... 77 4.2.8 Femur ........................................................................................................................ 80 4.2.9 Tibia ........................................................................................................................... 85 4.2.10 Fibula ...................................................................................................................... 88 4.2.11 Pes .......................................................................................................................... 91 4.3 Results of cladistic analysis ................................................................................. 100 5. DISCUSSION ....................................................................................................... 109 5.1 Just how quadrupedal was Antetonitrus? ........................................................... 109 5.1.1 Beyond Ratios: The range of motion in Antetonitrus as inferred from recent studies into sauropodomorph functional morphology. ............................................................................... 113 5.2 A brief word on early sauropod paleoecology ..................................................... 123 6. CONCLUSION ...................................................................................................... 127 7. REFERENCES ........................................................................................129 8. APPENDIX ...........................................................................................141 LIST OF FIGURES Figure 1: The Elliot Formation of South Africa ......................................................................... 4 Figure 2: Sauropodomorph phylogeny from Langer et al. (2010a) ......................................... 16 Figure 3: Isolated centra .......................................................................................................... 38 Figure 4: Mid-anterior dorsal neural arch .............................................................................. 42 Figure 5: Mid-posterior dorsal neural arch ............................................................................. 44 Figure 6: Posterior dorsal neural arch ..................................................................................... 47 Figure 7: ?Caudosacral neural arch & anterior caudal vertebra ............................................. 50 Figure 8: Mid-caudal vertebra and chevrons .......................................................................... 52 Figure 9: Scapula ...................................................................................................................... 56 vi Figure 10: Humerus ................................................................................................................. 60 Figure 11: Ulna ......................................................................................................................... 64 Figure 12: Radius ..................................................................................................................... 66 Figure 13: Metacarpal I ...........................................................................................................
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