Phylogenetic, Ontogenetic, and Functional Implications of Hominoid Mandibular Corpus Shape Variation by Mary Kathleen Pitirri A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Anthropology University of Toronto 2019 Phylogenetic, Ontogenetic, and Functional Implications of Hominoid Mandibular Corpus Shape Variation by Mary Kathleen Pitirri Department of Anthropology University of Toronto 2019 Abstract Mandibular fragments are among the most commonly preserved elements in the primate fossil record. These specimens are often studied through linear measurements of mandibular corpus height and breadth, which are used to calculate mandibular robusticity (MR). Presently, the significance of mandibular corpus variation in both living and fossil hominoids remains unclear. Here, three separate analyses are conducted to develop and evaluate an alternative method to quantify hominoid mandibular corpus shape and to investigate the dietary, phylogenetic and ontogenetic significance of hominoid mandibular corpus shape variation in order to help interpret corpus shape variation in the primate fossil record. These analyses use landmarks and semilandmarks to capture the shape of the outline of the mandibular corpus in cross-section in a sample of extant great apes, corporal cortical bone distribution (CBD) in a sample of extant and fossil hominoids, and to assess ontogenetic changes in corpus shape and the ii relationship between these changes and molar crypt length, breadth and height in a sample of extant hominoids. These results show that quantification and comparison of the shape mandibular corpus in cross-section is a preferred alternative to MR in studying the hominoid fossil record. Additionally, extant hominoids are found to have significant CBD shape differences that are phylogenetically significant and do not match morphological predictions based on diet. Investigation into ontogenetic changes in corpus shape shows clear differences in growth patterns among all three species prior to the emergence of M1, and finds a significant covariance between molar crypt form and corpus shape during the developmental stage marked by the emergence of M1. This research is significant because it provides support for the hypothesis that hominoid mandibular corpus shape is influenced by the development of the molars in their crypts during development. These results also indicate that both corpus shape and corporal CBD shape are taxonomically and phylogenetically significant and do not match morphological predications based on diet in hominoids. Additionally, this research shows that quantification and comparison of the outline of the mandibular corpus is a preferred alternative to MR in studying the hominoid fossil record. iii Acknowledgements I would like to take this opportunity to express my gratitude to my exceptionally patient and supportive doctoral supervisor, David Begun. It has taken us a very long time to get here. You inspired me as an undergraduate student to change the course of my life to this point. You tolerated every annoying question, every stupid idea and every terrible sentence with unwavering support. I’ve learned so much from you and I cannot thank you enough for everything you have done for me. I am also indebted to the other members of my core committee, Mary Silcox and Michael Schillaci. Without your guidance and input I would have been lost. Your dedication to me as your student has given me such an amazing opportunity to learn and grown into a much stronger researcher than I would have without you. I would also like to thank Jay Kelley for access to invaluable scans of fossil material and for his collaborative input in this research. Additionally, I would like to thank the Smithsonian’s Division of Mammals and Human Origins Program for the scans of USNM specimens and Dr. Emmanuel Gilissen for use of the scans of the RMCA specimens in this research. Finally, I would like to thank my family and friends for their encouragement and support during every step of this process. Steve Dorland and Amy Beresheim thanks for the coffee breaks, football games and nights out. Halszka Glowacka, thank you for expertise, proof reading and decades of friendship. Mom, Connie, Jim, Ang, Tam, Dee, Will, Nick and RJ thank you for everything you have done to encourage me from childhood through to adulthood. To Ben and Russ, thank you for inspiring me to achieve my goals, hopefully I am giving you the same gift. iv Table of Contents Abstract ........................................................................................................................................... ii Acknowledgements ........................................................................................................................ iv List of Tables ............................................................................................................................... viii List of Figures ................................................................................................................................ xi List of Appendices ....................................................................................................................... xiii List of Appendix Figures ............................................................................................................. xiii Chapter 1 Introduction .....................................................................................................................1 1.1 Background ............................................................................................................................2 1.1.1 Diet and the Hominoid Mandibular Corpus ....................................................................2 1.1.2 Growth and the Hominoid Mandibular Corpus ...............................................................6 1.1.3 Phylogeny and the Hominoid Mandibular Corpus ..........................................................7 1.1.4 Measuring the Hominoid Mandibular Corpus .................................................................8 1.2 Research Goals .......................................................................................................................9 1.3 Organization of Thesis ...........................................................................................................9 1.4 Literature Cited ....................................................................................................................10 Chapter 2 A New Method to Quantify Mandibular Corpus Shape in Extant Great Apes: Implications for Interpreting the Hominid Fossil Record. .............................................................20 2.1 Abstract ................................................................................................................................20 2.2 Introduction ..........................................................................................................................21 2.3 Materials and Methods .........................................................................................................24 2.3.1 Sample ...........................................................................................................................24 2.3.2 MR Data Acquisition and Analyses ..............................................................................24 2.3.3 Corpus Outline Data Acquisition and Analyses ............................................................25 2.3.4 Comparison of MR with Analysis of Corpus Outline Shape ........................................27 2.4 Results ..................................................................................................................................27 2.4.1 Analysis of Corpus Shape from MR Approach ............................................................27 2.4.2 Analysis of Corpus Outline Shape ...............................................................................30 2.4.3 Comparison of MR Analysis with Analysis of Corpus Outline Shape ........................33 2.5 Discussion ...........................................................................................................................37 2.6 Conclusion ...........................................................................................................................38 2.7 Literature Cited ....................................................................................................................39 v Chapter 3 Functional and Phylogenetic Implications of Cortical Bone Distribution in the Mandibular Corpus of Extant and Fossil Great Apes. ...................................................................48 3.1 Abstract ................................................................................................................................48 3.2 Introduction ..........................................................................................................................49 3.3 Materials and Methods .........................................................................................................58 3.3.1 Sample ...........................................................................................................................58 3.3.2 Data Acquisition ...........................................................................................................59 3.3.3 Geometric Morphometric Analysis ...............................................................................62 3.3.4