Reevaluating Maniraptoran Pelvic Musculature: Cursoriality, Convergence, and Caudal Decoupling by Matthew Michael Rhodes A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Systematics and Evolution Department of Biological Sciences University of Alberta © Matthew Michael Rhodes, 2019 Abstract Maniraptora is a clade of non-avian theropod dinosaurs comprising avians and several “bird-like” groups with semilunate wrist bones. Maniraptorans tend to exhibit anterior migration in centre of mass, enlargement of the pectoral region, and progressive decrease in tail length and bulk. This culminates in birds with a habitually crouched posture, development of wings, and radical reorganization of leg and tail musculature that caused profound changes in locomotion. However, the evolution of these archetypal “avian” features is not entirely understood. Thus, a desire exists to characterize how and when these adaptations were acquired, and the resultant palaeobiological effects. Did these changes affect running ability (cursoriality)? Were similar adaptations gained independently (convergence)? Did disentanglement of tail from hip musculature (caudal decoupling) also proceed in a stepwise fashion, mirroring reduction of the tail as a whole? Previous studies addressing these questions have tended to focus strictly on osteology. However, soft tissue reconstruction affords a new perspective not possible using only skeletal. Furthermore, does soft tissue evidence corroborate adaptations inferred from osteology? Relatively recent fossil discoveries of caenagnathids, dromaeosaurids, therizinosaurians, and troodontids permit reconstruction of maniraptoran locomotory musculature to infer adaptations and compare to skeletal evidence. Major locomotory muscles moor to the pelvis, which is also a junction between the leg and the tail. Direct observation of fossil pelvic material for osteological correlates of muscle attachments was done with reference to the closest living relatives to infer the presence or absence of major locomotory muscles. Extant conditions were determined by dissection and supplemented by literature review on soft tissue morphology and homology. Relative sizes of muscles and muscle groups allowed qualitative comparison within and between theropod taxa. ii Skeletal and myological inferences are variably consistent. In the therizinosaurian Falcarius, muscular reconstruction reveals reduction in major leg extensors. This is consistent with therizinosaurian evolution but suggests that basal maniraptorans had a punctuated onset of caudal decoupling. In Caenagnathidae, moderate reduction of major leg extensors contradicts alleged high cursoriality inferred from limb proportions and metatarsus structure, but corroborates gradual, progressive caudal decoupling preceding the evolution of birds. Troodontid muscular reconstruction instead upholds postulated high cursoriality in derived members, an adaptation gained secondarily and predominantly owing to intrinsic hip muscles. In Dromaeosauridae, the microraptorine lateral pubic tubercle is considered homologous with other osteological correlates of the pubogastralial ligament. The relationship between the tubercle and the pubic apron, to which locomotory muscles attach, may explain why a pronounced tubercle or process is unique to Microraptorinae. Reconstruction of maniraptoran pelvic musculature reveals a complex relationship with skeletal data. However, this facilitates a reevaluation of locomotory adaptations such as cursoriality, convergence, and caudal decoupling in non-avian maniraptorans. iii Preface Some of the research conducted for this thesis forms part of collaborative research, led by Matthew Rhodes and including colleagues at the University of Alberta. G. F. Funston provided a caenagnathid silhouette for modified use in Figures 1.1, 2.1, 3.1, 4.1, 5.1, and 6.2. All measurements and general descriptions of pelvic morphology presented in this thesis were respectively taken and written by the author. P. J. Currie was the supervisory author and was involved with concept formation and manuscript edits for all chapters. At the time of thesis submission, all four data chapters had been submitted for consideration of publication. Chapter 2 was submitted as Rhodes, M. M. and Currie, P. J., “Pelvic myology of the basal therizinosaurian Falcarius and evolution of locomotion in Therizinosauria and Maniraptora” to The Anatomical Record. I conducted data collection, analysis, and manuscript writing, and P. J. Currie provided manuscript edits. Chapter 3 was submitted as Rhodes, M. M., Funston, G. F., and Currie, P. J., “New material reveals the pelvic myology of Caenagnathidae (Theropoda, Oviraptorosauria)” to Cretaceous Research. G. F. Funston and I performed data collection and analysis, morphological interpretation, and manuscript writing. P. J. Currie contributed to manuscript edits. Chapter 4 was submitted as Rhodes, M. M. and Currie, P. J., “Troodontid pelvic myology offers insight into the convergence of cursoriality in Theropoda” to Palaeontology. I did data collection, analysis, and manuscript writing. P. J. Currie added to data collection, manuscript edits, and provided specimen photographs and data of some troodontid pelvic material that was also used in Figure 5.13. Chapter 5 was submitted as Rhodes, M. M. and Currie, P. J. “The homology, form, and function of the microraptorine lateral pubic tubercle” to Journal of Vertebrate Paleontology. I conducted data collection, analysis, and manuscript writing. P. J. Currie offered manuscript edits. iv Selected Quote “Any one of the larger carnivorous dinosaurs would meet the case. Among them are to be found all the most terrible types of animal life that have ever cursed the Earth or blessed a museum.” ~ Doyle 1912, p. 100, “The Lost World” (Professor Challenger simultaneously describing the ferocity, public appeal, and enigmatic essence of non-avian theropod dinosaurs) v Acknowledgements I firstly thank my supervisor P. J. Currie for his contributions both integral and peripheral to this thesis. This includes guiding research, mentorship, and leading field crews that have prepared me for lab and field work alike. I thank M. W. Caldwell for guidance and support despite my clear affliction with “dinosaur syndrome”. On more than a few occasions, my ability to critically analyze and assess various concepts was tested, but simultaneously improved. I also thank E. B. Koppelhus for assistance and encouragement throughout my program, especially for reminding me about the wonderful world of fossil plants. I am grateful for the advice and patience of my committee as it kept my program on track and developed my abilities as a researcher. Funding that enabled research for this thesis was generously provided by the Department of Biological Sciences, Dinosaur Research Institute, Government of Alberta, Graduate Students’ Association, Natural Sciences and Engineering Research Council of Canada, and University of Alberta Faculty of Graduate Studies and Research. For access to collections, I thank R. Esplin and R. Scheetz (BYUVP); K. Corneli and K. Carpenter (CEUM); J. Mallon, K. Shepherd, and M. Currie (CMN); A. Atwater and J. Scannella (MOR); A. Howell (RM); B. Iwama and K. Seymour (ROM); B. Strilisky and D. Brinkman (TMP); C. Coy and H. Gibbins (UALVP); B. Barr (UAMZ); and C. Levitt-Bussain and R. Irmis (UMNH). The hospitality and assistance provided made for enjoyable collections visits and helped me to find some fantastic specimens that I may have otherwise overlooked. I owe appreciation to the many folks of my cohort that contributed in major and minor ways. I thank T. Miyashita for counsel and meaningful, thought-provoking questions that provided timely motivation to refocus on the bigger picture. I thank G. Funston, whose wit kept me on my toes to try and match his many quips, but whose intellect also helped to adjust my vi approach to various research problems. I thank M. Powers for discussions and banter that balanced work and fun in the field, in the lab, and on our many research trips. I also thank my other former and current lab mates and cohorts (A. Dyer, A. LeBlanc, A. van der Reest, A. McIntosh, B. Stettner, F. Garberoglio, I. Paparella, K. Bramble, M. Campbell-Mekarski, M. Dueck, O. Vernygora, P. Jiménez Huidobro, R. Vice, S. Hamilton, S. Mohr, S. Persons, S. Sinha, T. Simões, and Y. Wang) for discussion, positivity, and fun at social gatherings over the years. To others that helped in academic ways or alleviating conversations during my graduate studies, I thank A. Murray, A. Richard Palmer, A. Rhodes, A. Torices, B. Barr, C. Hatley, C. Sullivan, D. Evans, D. Henderson, D. Brinkman, G. Bradley, J. Theodor, J. Voris, M. Pruden, R. Brown, R. Dievert, R. Holmes, R. Nottrodt, R. Sissons, and V. Arbour. Regarding fossil preparation, I thank A. Lindoe for technical advice and countless puns, and Evening Dino Lab volunteers for company and conversation during weekly sessions. Additionally, I thank T. Trump for being a great roommate while we tackled our theses. I am also grateful for other friends, family, and colleagues not explicitly mentioned that made their impact along the way. A great deal of gratitude goes to Mom, Dad, Kathryn, Grandma, and Grandpa for their unwavering love and support that encouraged me to chase my dreams and bestowed me with the skills to do so. I deeply appreciate their tolerance for obscure anatomical and veterinary questions, patience during excited but lengthy