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Braincase Anatomy in Non-Neosauropodan Sauropodomorphs: Evolutionary and Functional Aspects

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Braincase Anatomy in Non-Neosauropodan Sauropodomorphs: Evolutionary and Functional Aspects Braincase anatomy in non-neosauropodan sauropodomorphs: evolutionary and functional aspects Dissertation der Fakultät für Geowissenschaften der Ludwig- Maximilians-Universität München zur Erlangung des Doktorgrades in den Naturwissenschaften (Dr. rer. nat.) Vorgelegt von Mario Bronzati Filho München, 15. März 2017 Erstgutachter: PD Dr. Oliver Rauhut Zweitgutachter: Prof. Dr. Max Cardoso Langer Tag der mündlichen Prüfung: 26.09.2017 I Statutory declaration and statement I hereby confirm that my thesis entitled “Braincase anatomy in non-neosauropodan sauropodomorphs: evolutionary and functional aspects”, is the result of my own original work. Furthermore, I certify that this work contains no material which has been accepted for the award of any other degree or diploma in my name, in any university and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text. In addition, I certify that no part of this work will, in the future, be used in a submission in my name, for any other degree or diploma in any university or other tertiary institution without the prior approval of the Ludwig- Maximilians-University Munich. II Contents Statutory declaration and statement II Abstract of the thesis VI Acknowledgements IX Chapter 1. Introduction 1 1.1. Introduction 2 1.2. Evolution of Sauropodomorpha 10 1.3. Braincase 13 1.4. Objectives of the dissertation 15 1.5. Overview of studies presented in Chapter 02 to Chapter 07 16 1.6. References 20 Chapter 2. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet 29 2.1. Abstract 31 2.2. Results 31 2.3. Discussion 37 2.4. Acknowledgements 41 2.5. References 41 Chapter 3. Early dinosaur brain indicates faunivorous exaptation in the early evolution of sauropodomorph herbivory 44 3.1. Abstract 45 3.2. Introduction 46 3.3. Results 48 3.4. Discussion 49 3.5. Material & Methods 55 3.6. Acknowledgements 57 III 3.7. References 58 Chapter 4. Braincase anatomy of the early sauropodomorph Saturnalia tupiniquim (Late Triassic, Brazil) 64 4.1. Abstract 65 4.2. Introduction 66 4.3. Material & Methods 68 4.4. Results 72 4.5. Discussion 109 4.6. Conclusions 122 4.7. References 123 Chapter 5. Braincase redescription of Efraasia minor (Huene, 1908) (Dinosauria, Sauropodomorpha) from the Late Triassic of Germany, with comments on the evolution of the sauropodomorph braincase 127 5.1. Abstract 128 5.2. Introduction 129 5.3. Material & Methods 131 5.4. Results 135 5.5. Discussion 184 5.6. Conclusions 218 5.7. Acknowledgements 220 5.8. References 221 Chapter 6. Rapid transformation in the braincase of sauropod dinosaurs: implications for the early evolution of gigantism 231 6.1. Abstract 232 6.2. Introduction 233 6.3. Material & Methods 235 6.4. Results 238 6.5. Discussion 245 IV 6.6. Conclusions 252 6.7. Acknowledgements 254 6.8. References 254 Chapter 7. Should the terms ‘basal taxon’ and ‘transitional taxon’ be extinguished from cladistic studies with extinct organisms? 260 7.1. Abstract 261 7.2. Plain Language Summary 262 7.3. Introduction 262 7.4. Discussion 266 7.5. Practical guidelines 279 7.6. Conclusions 280 7.7. Acknowledgements 281 7.8 References 281 Conclusions Appendix i Appendix Chapter 2 ii Appendix Chapter 3 xxvii Appendix Chapter 5 xxxvii Appendix Chapter 6 lxii V Abstract of the thesis The evolutionary history of sauropodomorphs starts in the Late Triassic, a period characterized by the extinction and radiations of distinct archosaur lineages. During the first c. 50 million years of sauropodomorph evolution, a great number of anatomical transformations are observed among non-sauropodan lineages of Sauropodomorpha, once thought as ‘typical herbivore’ and ‘conservative’. All these transformations are reflected in the morphological disparity observed among sauropodomorph dinosaurs. The earliest members of the group, from the Late Triassic (Carnian) were small animals, faunivorous and omnivorous, and with a bauplan that differs significantly from the quintessential representatives of the group, the gigantic sauropods, the biggest land animals that ever lived on Earth. This morphological disparity, alongside a rich and globally distributed fossil record, represents a very interesting case to study morphological changes within a lineage. Notwithstanding, the anatomy of sauropodomorph was the topic of many studies, mainly aiming to understand the origins of the peculiar and distinct sauropod bauplan, especially the transition from a bipedal to a quadrupedal stance, and the evolution of a fully herbivore diet. The aim of this study is an analysis of patterns of transformation of the braincase in sauropodomorph dinosaurs and their implications for our understanding concerning the phylogenetic relationships and palaeobiology of these animals. The analysis of two new fossils, the sauropodomorph dinosaur (Buriolestes schultzi) the lagerpetid (Ixalerpeton polesinensis), helps clarifying anatomical transformations of the braincase in the Dinosauromorpha lineage and the early evolution of dinosaur diets. The tooth morphology of Buriolestes indicates that it was a faunivorous animal. Thus, given its phylogenetic position as the sister group of all VI the other sauropodomorphs, and the faunivorous diet of theropods and herrerasaurids, the new data indicate that faunivory is the ancestral condition of Sauropodomorpha. The endocast of Saturnalia tupiniquim helps to understand one of the well- known traits of sauropodomorph dinosaurs, a short skull. Saturnalia has a well- developed flocculus (i.e. projecting into the space between the semi-circular canals of the inner ear), which is a feature observed in predatory dinosaurs, and absent in later sauropodomorphs, including sauropoda. Combining new information on the soft- tissues of the brain with data on skeletal anatomy and phylogeny of sauropodomorphs, it is proposed that skull reduction was firstly an adaptation to feed on small and elusive preys. As a small skull was later a ‘key’ trait for the evolution of a fully herbivorous diet (by diminishing the constraint on the neck), skull reduction in sauropodomorph can be now understood as an exaptation. The osteological descriptions of the braincases of Saturnalia tupiniquim and Efraasia minor allow tracing the evolution of braincase anatomy in Sauropodomorpha in more details. Comparisons with lagerpetids, silesaurids, and other dinosaurs showed that features once thought to be absent or less widespread in dinosaurs, such as the semilunar depression (or subotic recess) and a basioccipital and subsellar recesses, are in fact found among members of the three main lineages of Dinosaria, and also among non-dinosaurian dinosauromorphs. Furthermore, the results of a phylogenetic analysis focusing on non-neosauropodan sauropodomorphs indicate that despite the existence of characters supporting a monophyletic ‘Prosauropoda’ (i.e. a calde encompassing the non-sauropodan sauropodomorphs), constrained phylogenetic analyses indicate that the paraphyletic condition of ‘prosauropods’ in relation to Sauropoda is still a much stronger hypothesis. VII A great number of transformations in the braincase anatomy were also detected within sauropods in the phylogenetic analyses conducted for this thesis. Discrete character-taxon matrix analyses indicate a drastic transformation in the braincase of these animals in relation to their non-sauropodan relatives, with the results of a principal coordinate analysis showing that the morphospace occupation of sauropod braincases does not overlap with the morphospace of non-sauropodan sauropodomorpsh. Furthermore, analyses of rates of character evolution indicate that transformations shaping the braincase anatomy of sauropods occurred in a short period of time, during the Middle Jurassic, and can be linked to the further elongation of the neck also observed in Middle Jurassic taxa. Ultimately, these modifications in the cranio-cervical complex are likely related to a re-activation of the ‘neck and head’ cascade of gigantism, and potentially played a role in the differential survival of sauropodomorphs in the Early-Middle Jurassic. Finally, differently from what is stated in a great number of previous studies on the evolution of Sauropodomorpha, the non-sauropodan sauropodomorphs (or “prosauropod”) do not represent transitional forms between the hypothetical ancestor of Sauropodomorpha and Sauropoda. Nevertheless, sauropods and ‘prosauropods’ share part of their evolutionary history, and the data presented here emphasizes that tracing anatomical transformation in non-sauropodan lineages is crucial to understand the evolution of the gigantic sauropods. VIII Acknowledgements I would like to thank my supervisor Oliver Rauhut (Oli), who supported my scientific work and gave me the possibility to wrap my brain around braincases over the last three and half years of my life. I further thank my first (and still?) supervisor Max C. Langer, who gave me the possibility to study the braincase of one of the oldest dinosaurs, what a privilege. I am also especially thankful to Claudia Malabarba, Marco Brandalise de Andrade, Rainer Schoch, Daniela Schwarz, Jay Nair, and Roger Benson for the opportunity to study the braincase of ‘a lot’ of sauropodomorphs. Another thanks goes to all my co-authors, Roger Benson, Jonathas Bittencourt, ‘The Ixalerpeton and Buriolestes team’, and of course Max and Oli, without whom I would not be able to get to work on the most distinct and
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