Inferring Body Mass in Extinct Terrestrial Vertebrates and the Evolution of Body Size in a Model-Clade of Dinosaurs (Ornithopoda) by Nicolás Ernesto José Campione Ruben A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Ecology and Evolutionary Biology University of Toronto © Copyright by Nicolás Ernesto José Campione Ruben 2013 Inferring body mass in extinct terrestrial vertebrates and the evolution of body size in a model-clade of dinosaurs (Ornithopoda) Nicolás E. J. Campione Ruben Doctor of Philosophy Ecology and Evolutionary Biology University of Toronto 2013 Abstract Organismal body size correlates with almost all aspects of ecology and physiology. As a result, the ability to infer body size in the fossil record offers an opportunity to interpret extinct species within a biological, rather than simply a systematic, context. Various methods have been proposed by which to estimate body mass (the standard measure of body size) that center on two main approaches: volumetric reconstructions and extant scaling. The latter are particularly contentious when applied to extinct terrestrial vertebrates, particularly stem-based taxa for which living relatives are difficult to constrain, such as non-avian dinosaurs and non-therapsid synapsids, resulting in the use of volumetric models that are highly influenced by researcher bias. However, criticisms of scaling models have not been tested within a comprehensive extant dataset. Based on limb measurements of 200 mammals and 47 reptiles, linear models were generated between limb measurements (length and circumference) and body mass to test the hypotheses that phylogenetic history, limb posture, and gait drive the relationship between stylopodial circumference and body mass as critics suggest. Results reject these and instead ii recover a highly conserved relationship that provides a robust method to estimate body mass in extinct quadrupedal tetrapods. The constrained model is then used to derive a mathematical correction that permits the body mass of bipedal taxa to be estimated from the quadrupedal-based equation. These equations thus form the empirical baseline dataset with which to assess the accuracy of mass estimates derived from volumetric reconstructions, which, although subjective, are crucial for interpreting biomechanical and physiological attributes in extinct forms. The models developed through this research provide accurate and consistent estimates of body size in terrestrial vertebrates, with important implications for generating large datasets aimed at reconstructing macroevolutionary patterns of body size in association with changing Earth systems. iii I dedicate this thesis to my greatest contribution, Dominic, whom I can’t wait to run through a dinosaur gallery with; to my wife Michelle for always being by my side and emotionally supporting me over the past 5 years of this work; to Sofía and Alejandro for being the greatest sister and brother; and lastly, to my parents José Campione and Martha Ruben for encouraging my love for science from a young age, and in particular for taking me to la Isla de las Ardillas (a.k.a.,Victoria Island, on the Ottawa River) about 25 years ago, where I found my first fossil (an Ordovician cephalopod). iv Acknowledgments When I began my journey to complete a PhD in September 2008, I could not have imagined the plethora of people that would be integral to its completion. Over the past five years I have had the pleasure of meeting and discussing my research with some of the best palaeobiologists and evolutionary biologists in the world and through their experiences and knowledge I have learned an amazing range of both theoretical and methodological concepts that have made me the scientist I am today. First and foremost I need to thank my supervisor David Evans. I am David’s first PhD student and I could not be more certain that I made the right choice five years ago when I joined the then young Evans lab. David has provided me with all the necessary tools and guidance that I needed not only to complete this PhD but also prepare me for an academic career. Dave, I will forever cherish our numerous travels around the world. Second, I must thank Robert Reisz, my co-supervisor. Robert supported my desire to pursue graduate school, supporting me through my M.Sc., and being a great resource with whom to discuss results and implications. Two world- class biologists round out my supervisory committee: Matthew Carrano has been pivotal in discussing and suggesting methods critical to this project, as well as sharing personal data and greatly improving the quality of my PhD; and Daniel Brooks has been central in getting me to think a bit broader about the significance of my work. My appraisal examination committee has been critical for expanding my horizons and directing me along the right research path. For this I thank Jason Head and Deborah MacLennan. v I am indebted to the members of the Evans and Reisz labs. Without you guys, I would not have been able to keep my sanity over the last five years. You have not only helped me academically (putting up with my ill-prepared talks and manuscripts) and in pursuing new avenues of research (a.k.a, side projects) but also emotionally over beers or coffee. Thank you Kirstin Brink, Caleb Brown, Kentaro Chiba, Daniel Dufault, Derek Larson, Aaron Leblanc, David Mazierski, Christopher McGarrity, Lorna O’brien (Honorary Member), Collin VanBuren, Ryan Schott, Diane Scott, and Matthew Vavrek. In particular, I need to thank Matthew Vavrek for his amazing help with R; if I know anything about R now, it’s because of you. Caleb, thank you for your help with deriving the correction factor (a.k.a., the Brown Constant) and for showing me the secrets to good figure making. Kirstin, thank you for making everyday Friday! Along the way, I have had the honour of discussing my doctoral research with several awe-inspiring researchers that have taken the time to share their thoughts; all of whom have helped me arrive to this point in my life: John Alroy, Jason Anderson, Jessica Arbour, Paul Barrett, Stephen Brusatte, Richard Butler, Per Christiansen, Philip Currie, Robin Cuthbertson, Alexander Dececchi, Jerry De Iulius, Peter Dodson, Richard Fariña, Denver Fowler, Jörg Fröbisch, Nadia Fröbisch, Stephen Gatsey, Donald Henderson, John Horner, Grant Hurlburt, John Hutchinson, Donald Jackson, Matthew Lamanna, Hans Larsson, Michel Laurin, Hernan Lopez-Fernandez, Hillary Maddin, Susannah Maidment, Jordan Mallon, Philip Manning, Albert Prieto-Márquez, Michael Ryan, Natalia Rybczynski, Rowan Sage, Martin Sanders, John Scannella, Mary Silcox, Corwin Sullivan, Matthew Wedel, and David Weishampel. Numerous individuals have helped on specific aspects of my research; in particular Roger Benson has been an invaluable resource for discussing and understanding methods for reconstructing evolutionary patterns of body size; Lars Schmitt helped with conducting vi independent contrasts analyses; Roland Sookias, provided R-code and help in reproducing some of his previous research on my dataset; David Warton aided in understanding linear model- fitting techniques in R; and both Graham Slater and David Bapst (through the R-sig-phylo List) helped understand errors when running model-fitting analyses on phylogenetic trees. My doctoral research relied on numerous collections and museum staff in order to reach completion. In particular, I am indebted to the efforts of Kevin Seymour, Suzan Woodward, Mark Peck, and Ross MacCulloch at the ROM, without whom the extant datasets presented in this thesis would not have been possible. They have amassed one of the most useful collections in world in which skeletonized specimens are directly associated with body mass data. For their help with accessing and handling specimens I thank Kevin Seymour, Ian Morrison, and Bian Iwama (ROM); Kieran Shephard, Margaret Currie, Alan MacDonald, and Clayton Kennedy (CMN); Brendan Strilisky (TMP); Mogen Andersen (ZMUC); Paul Barrett (NHM); Pascal Godefroit, Pascaline Lauters, and Annelise Folie (IRSNB); Corwin Sullivan and Xu Xing (IVPP), Carl Mehling and Mark Norell (AMNH), Amy Henrici (CM); Peter Larson (BHI); Chinzorig Tsogtbaatar and Khishigjav Tsogtbaatar (MPC); John Horner (MOR); and Michael Brett-Surman (USNM). Finally, but definitely not least I thank my family: my wife Michelle Campione van Zetten and my baby boy Dominic, thank you for following me in this crazy dream of mine; my parents José Campione and Martha Ruben for always believing in me; my sister Sofía Campione and brother Alejandro Campione for their love and always being around to talk; to my niece Anya Campione for always being keenly aware that I like dinosaurs; to my in-laws Debbie and John van Zetten; and finally to my large family in Uruguay. You’ve all supported me vii emotionally (and sometimes financially) and I cannot imagine being here today without you, los quiero mucho! viii Table of Contents ACKNOWLEDGMENTS ........................................................................................................... V TABLE OF CONTENTS ........................................................................................................... IX LIST OF TABLES ................................................................................................................... XIII LIST OF FIGURES ................................................................................................................... XV LIST OF APPENDICES .....................................................................................................