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Skull Anatomy and Relationships of Jingshanosaurus Xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China By

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Skull Anatomy and Relationships of Jingshanosaurus Xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China By Skull Anatomy and Relationships of Jingshanosaurus xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China by Joshua Sundgren, B.S. A Thesis In Geoscience Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved Dr. Sankar Chatterjee Chair of the Committee Dr. Thomas Lehman Dr. James Barrick Mark Sheridan Dean of the Graduate School May, 2021 Copyright 2021, Joshua Sundgren Texas Tech University, Joshua Sundgren, May 2021 ACKNOWLEDGEMENTS First, I would like to thank my advisor and committee chair, Dr. Sankar Chatterjee, for giving me this incredible opportunity. His support and guidance have been invaluable while working on this project, especially with all of the challenges over the past year. I would also like to thank my other committee members, Dr. James Barrick and Dr. Tom Lehman, for all of their assistance, both on this project and throughout my entire time at Texas Tech. I am extremely grateful to Kendra Dean-Wallace and John-Henry Voss of the Museum of Texas Tech University for their help throughout all stages of this project. I would also like to thank Dr. Hai-Lu You of the Institute of Vertebrate Paleontology and Paleoanthropology for providing the phylogenetic data which played such a key role in this research. I am very appreciative of all of the help I’ve received from Celeste Yoshinobu, throughout my entire time at Texas Tech University. Finally, I cannot thank my parents, Gary and Stacy, enough for all of their support and everything they have done for me. I would not be where I am today without them. ii Texas Tech University, Joshua Sundgren, May 2021 TABLE OF CONTENTS ACKNOWLEDGEMENTS .................................................................................... ii ABSTRACT .............................................................................................................v LIST OF FIGURES .............................................................................................. vi 1. INTRODUCTION ...............................................................................................1 1.1 Materials and Methods ....................................................................................9 1.2 Institutional Abbreviations .............................................................................10 2. GEOLOGIC SETTING .....................................................................................11 3. PREVIOUS WORK ...........................................................................................21 3.1 “Gyposaurus” sinensis ...............................................................................21 3.2 Lufengosaurus ............................................................................................22 3.3 Yunnanosaurus ...........................................................................................24 3.4 Chuxiongosaurus .......................................................................................27 3.5 Xixiposaurus ..............................................................................................28 3.6 Xingxiulong ................................................................................................28 3.7 Yizhousaurus ..............................................................................................30 3.8 Irisosaurus .................................................................................................32 3.9 Jingshanosaurus ........................................................................................34 4. SKULL DESCRIPTION OF JINGSHANOSAURUS ........................................37 4.1 General Features ........................................................................................37 4.2 Dermal Bones of the Skull Roof ................................................................38 4.2.1 Premaxilla .........................................................................................38 4.2.2 Maxilla ..............................................................................................39 4.2.3 Nasal .................................................................................................40 4.2.4 Frontal ...............................................................................................41 4.2.5 Prefrontal...........................................................................................42 4.2.6 Postorbital .........................................................................................42 4.2.7 Quadrate ............................................................................................43 4.3 Palatal Complex .........................................................................................46 4.3.1 Vomer ...............................................................................................46 4.3.2 Pterygoid ...........................................................................................46 4.3.3 Ectopterygoid ....................................................................................47 4.4 Lower Jaw ..................................................................................................50 iii Texas Tech University, Joshua Sundgren, May 2021 4.4.1 Dentary ..............................................................................................50 4.4.2 Surangular .........................................................................................51 4.4.3 Articular ............................................................................................51 4.5 Dentition ....................................................................................................55 5. PHYLOGENETIC ANALYSIS ........................................................................60 6. SUMMARY .......................................................................................................64 BIBLIOGRAPHY ..................................................................................................66 APPENDICES A. LIST OF PHYLOGENETIC CHARACTERS .................................................74 iv Texas Tech University, Joshua Sundgren, May 2021 ABSTRACT The basal sauropodomorphs are an important group of saurischian dinosaurs which include some of the earliest dinosaurs known to researchers, with the oldest taxa dating to the Late Triassic. Different members of the basal sauropodomorphs are closely related to several other groups, including the immediate ancestors to dinosaurs, theropods, and the true sauropods. Because of these close relations, a good understanding of the phylogenetic relationships between the basal sauropodomorphs is key to a broader understanding of early dinosaurs. Jingshanosaurus xinwaensis is an Early Jurassic sauropodomorph which has been recovered previously as a basal member of the clade Sauropodiformes, which eventually gave rise to the true sauropods. However, J. xinwaensis has suffered from a lack of cranial material for research, a problem that this study addresses. Specimen IVPP-13246 consists of 14 previously undescribed and disarticulated cranial bones from the skull roof, palatal complex and the lower jaw, as well as teeth preserved in good condition. The teeth are of particular interest partially because of their condition and also because of their unique form which is more similar to those seen in sauropods than in basal sauropodomorphs. These bones are described here and have characters scored and entered into a data matrix from another recent study. A phylogeny is then reconstructed from this data using PAUP*4.0a169. The results of this analysis do not show Jingshanosaurus as having changed position which lends robust support to the findings of previous studies. There is potential for future studies, particularly in relation to bones that had not been described for earlier skulls, such as the nasal and the vomer. v Texas Tech University, Joshua Sundgren, May 2021 LIST OF FIGURES 2.1 Earth in the Early Jurassic ..........................................................................12 2.2 Lufeng, China ............................................................................................15 2.3 Detailed Locality Map ...............................................................................17 2.4 Stratigraphy Column ..................................................................................19 4.1 Jingshanosaurus skull ................................................................................37 4.2 Bones of the Skull Roof .............................................................................44 4.3 Line drawings of skull roof bones .............................................................45 4.4 Palate Bones ...............................................................................................48 4.5 Line drawings of palatal complex bones ...................................................49 4.6 Lower Jaw Bones .......................................................................................53 4.7 Line drawings of lower jaw bones .............................................................54 4.8 Jingshanosaurus dentition .........................................................................58 4.9 Line drawings of Jingshanosaurus dentition ..............................................59 5.1 Sauropodomorph Phylogeny ......................................................................62 vi Texas Tech University, Joshua Sundgren,
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