Functional Morphology of the Vertebral Column in Remingtonocetus (Mammalia, Cetacea) and the Evolution of Aquatic Locomotion in Early Archaeocetes by Ryan Matthew Bebej A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Ecology and Evolutionary Biology) in The University of Michigan 2011 Doctoral Committee: Professor Philip D. Gingerich, Co-Chair Professor Philip Myers, Co-Chair Professor Daniel C. Fisher Professor Paul W. Webb © Ryan Matthew Bebej 2011 To my wonderful wife Melissa, for her infinite love and support ii Acknowledgments First, I would like to thank each of my committee members. I will be forever grateful to my primary mentor, Philip D. Gingerich, for providing me the opportunity of a lifetime, studying the very organisms that sparked my interest in evolution and paleontology in the first place. His encouragement, patience, instruction, and advice have been instrumental in my development as a scholar, and his dedication to his craft has instilled in me the importance of doing careful and solid research. I am extremely grateful to Philip Myers, who graciously consented to be my co-advisor and co-chair early in my career and guided me through some of the most stressful aspects of life as a Ph.D. student (e.g., preliminary examinations). I also thank Paul W. Webb, for his novel thoughts about living in and moving through water, and Daniel C. Fisher, for his insights into functional morphology, 3D modeling, and mammalian paleobiology. My research was almost entirely predicated on cetacean fossils collected through a collaboration of the University of Michigan and the Geological Survey of Pakistan before my arrival in Ann Arbor. Iyad S. Zalmout collected the new specimen of Remingtonocetus domandaensis described in Chapter 3 (as well as many others), and he generously permitted me to study this remarkable specimen for my dissertation work. Others who collected the fossils utilized in my work include Mohammad Anwar, Muhammad Arif, M. Akram Bhatti, William C. Clyde, Philip D. Gingerich, Munir ul-Haq, iii Intizar Hussain Khan, William J. Sanders, and Neil A. Wells. I especially thank William J. Sanders for skillfully preparing these fossils; patiently training me in the art of preparing, molding, and casting fossils; and for all of our stimulating and insightful discussions about vertebral biomechanics, the evolution of cetaceans in general, and, on occasion, the St. Louis Cardinals vs. the New York Mets. My research would also not have been possible without access to specimens of both modern and fossil mammals for comparison. I thank the following people for access to specimens in their care: Steve Hinshaw, Philip Myers, and Priscilla Tucker in the Mammal Division at the University of Michigan Museum of Zoology (Ann Arbor, MI); Judy Galkin and Eileen Westwig at the American Museum of Natural History (New York, NY); and David Bohaska, Linda Gordon, Jeremy Jacobs, and Charlie Potter at the National Museum of Natural History (Washington, DC). My dear friends Kyle and Michele Peterson graciously provided me with food, lodging, and wonderful tours of the District of Columbia during multiple research visits to the National Museum. Many faculty, staff members, post-docs, and fellow students contributed to making the University of Michigan Museum of Paleontology a wonderful and vibrant place to work, including Catherine Badgley, Tom Baumiller, Robyn Burnham, Devapriya Chattopadhyay, Mike Cherney, Mike D’Emic, Tom Eiting, Julia Fahlke, John Finarelli, Brady Foreman, John Graf, Gregg Gunnell, Amber Heard, Takehito Ikejiri, Alex Janevski, Cait Lamborne, Carly Manz, Amy McKeighan, Dan Miller, Chrissy Minor, Vlad Miskevich, Pieter Missiaen, Emile Moacdieh, Meegan Novara, Shanan Peters, Gerald Smith, Cindy Stauch, John Whitlock, Jeff Wilson, Miriam Zelditch, and the myriad of students working iv in the prep lab. Bonnie Miljour provided the beautiful reconstruction of R. domandaensis (see the frontispiece and Chapter 3), along with invaluable help in navigating Adobe Photoshop and Illustrator. Adam Rountrey was an invaluable resource on many topics, especially 3D scanning and modeling, and Katy Smith offered innumerable discussions about mammalian evolution, multivariate statistics, the latest episode of Lost, and Major League Baseball. I will forever be indebted to Aaron Wood for his depth of insight, his listening ear, his unwavering advice, and, most of all, his friendship. I am also grateful for many faculty, staff members, and students in the Department of Ecology and Evolutionary Biology (EEB), including Prosanta Chakrabarty, Clay Cressler, Deborah Goldberg, Aaron Iverson, Mandy Izzo, George Kling, Gail Kuhnlein, Jessica Middlemis Maher, the late Beverly Rathcke, Nancy Smith, and Rachel Vannette. Julia Eussen and Jane Sullivan were fabulous graduate coordinators, and I am thankful for their willingness to deal with and answer any question, no matter how inane. My experiences teaching with Marc Ammerlaan, Bill Fink, Phil Myers, and Ron Nussbaum were fantastic. But most of my favorite memories teaching are from my three semesters as co-graduate student instructor with Lucia Luna; she taught me so much, and her enthusiasm and humor always made my day. I also thank Chris Van Ee at Design Research Engineering (Novi, MI), whose time and expertise made it possible for me to develop the multibody dynamic models in Chapter 5; Brett Lyons and Eric Maslowski of the University of Michigan 3D Lab; my undergraduate mentors Ralph Stearley, Randy Van Dragt, and Dave Warners of Calvin v College (Grand Rapids, MI) for their continued encouragement and support; Rolf Bouma and all of the Au Sable Graduate Fellows who have come and gone in the past six years; and Matt Remy and Paul Steen for their camaraderie, graduate life commiseration, and board game acumen. Lastly, I must express my sincere gratitude to my family, especially my parents and my in-laws, for all of their love and support over the years. Most of all, I am extremely thankful to my wife Melissa, who has given and sacrificed so much for me as I pursued my dream. Her love, encouragement, smile, and culinary skills are appreciated far more than she could ever know. And last, but not least, I am grateful for my wonderful little dog Duncan, who has never failed to greet me with a wagging tail, a belly to scratch, and/or a lick on the face after coming home from a long day at work— and who also never seemed to mind that I tried to gain insight into vertebral function by staring at his lumbar region while he gallivanted around our apartment. This research was supported by EEB Block Grants, the Peter Olaus Okkelberg Award, and the University of Michigan Museum of Paleontology. vi Table of Contents Dedication ............................................................................................................................ ii Acknowledgments............................................................................................................... iii List of Figures ..................................................................................................................... xii List of Tables ...................................................................................................................... xv List of Abbreviations ........................................................................................................ xvii Abstract ............................................................................................................................. xix Chapter 1: Introduction ...................................................................................................... 1 Background ................................................................................................................... 1 Evolution of Aquatic Locomotion ................................................................................. 3 Changes in the Function of the Vertebral Column ....................................................... 6 The Archaeocete Family Remingtonocetidae ............................................................... 8 Overview ..................................................................................................................... 10 Figures ......................................................................................................................... 14 Table ............................................................................................................................ 18 References .................................................................................................................. 19 vii Chapter 2: Systematic Review of the Remingtonocetidae (Mammalia, Cetacea) ........... 33 Introduction ................................................................................................................ 33 Age of Remingtonocetid-Bearing Formations ............................................................ 34 Systematic Paleontology ............................................................................................. 37 Discussion.................................................................................................................... 54 Are Dalanistes and Remingtonocetus males and females of a single species? .... 54 Differences in Size Between Homologous Postcranial Elements ................... 58 Differences in Size Between Canine Teeth ..................................................... 60 Stratigraphic