Casuarius): a Case Study of Cranial
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ONTOGENY, DISPARITY, AND FUNCTION OF THE ENIGMATIC CASQUES OF CASSOWARIES (CASUARIUS): A CASE STUDY OF CRANIAL ORNAMENTATION IN ARCHOSAURS By TODD LANDON GREEN Bachelor of Science in Biology; Zoology Colorado State University Fort Collins, Colorado 2008 Master of Science in Zoology Colorado State University Fort Collins, Colorado 2012 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY December, 2020 ONTOGENY, DISPARITY, AND FUNCTION OF THE ENIGMATIC CASQUES OF CASSOWARIES (CASUARIUS): A CASE STUDY OF CRANIAL ORNAMENTATION IN ARCHOSAURS Dissertation Approved: Paul M. Gignac, PhD Dissertation Adviser Haley D. O’Brien, PhD Holly N. Ballard, PhD Jennifer L. Volberding, PhD ii ACKNOWLEDGEMENTS This project has been fueled by lifelong interests in flightless birds and paleontology. My parents, Richard and Jane Green, helped cultivate my early passions for the natural world, and they have been an unwavering source of encouragement and inspiration. I am proud to be their son. To my partner Amie McCarthy, I thank you for your love, strength, and patience, particularly during the stressful periods of my doctoral program, as well as accompanying me to cassowary territory in Australia despite your demanding schedule. I express the sincerest gratitude to my advisor, Paul Gignac, whose generosity, compassion, and ravenous pursuit of knowledge exemplify the characters I aspire to attain as a professional scientist. I thank the other members of my committee, Haley O’Brien, Holly Ballard, and Jennifer Volberding, for their emotional support, feedback, and excitement for my project. Haley has taught me how to always strive to be better, and simultaneously kind to myself along the way. My lab mate, David Kay, has become a trustworthy and loyal colleague and friend, and there is no one I would have rather fought in the graduate student trenches with. I additionally thank all of the other paleontology faculty, biomedical faculty, staff, postdocs, graduate students, medical students, undergraduate researchers, and OKStars students at Oklahoma State University Center for Health Sciences that have helped me through this journey. This project would not have been possible without the constant support and generous cassowary access from R. Glenn Hood and Scott Snedecker (Cassowary Conservation Project; Fort Pierce, FL, USA). We are bonded by birds. Linn and Terry Turner (Rabbit Creek Emu Ranch; Livermore, CO, USA) have donated specimens over the course of my graduate career, and in the process have become an invaluable support system. We lost Linn during my time in this program, but I will always remember him standing beside the emus he loved. Other specimen access, data files, or regional information were provided by the considerate assistance of: Bentley Bird, Paul Sweet, Thomas Trombone (American Museum of Natural History; New York, NY, USA), Mark Balman (BirdLife International; Cambridge, UK), Leslie Boucher, Tony Boucher, Madison Boucher, Thomas Grazier (Boucher Family Farms, Longmont, CO, USA), M. David Quavillon, Michelle Ferguson, Ellen Dreyer, Michelle Smurl (Brevard Zoo; Melbourne, FL, USA), Jay Young (Colorado Gators; Mosca, CO, USA), Peter Rowles (Community for Coastal and Cassowary Conservation, Mission Beach, QLD, AU), Mark Corbridge, Tish Corbridge (Dream Acres Emu Ranch; Cheyenne, WY, USA), Garth Spellman, Jeff Stephenson, Andrew Doll (Denver Museum of Nature and Science; Denver, CO, USA), Thomas deMaar, Natalie Lindholm (Gladys Porter Zoo; Brownsville, TX, iii Acknowledgements reflect the views of the author and are not endorsed by committee members or Oklahoma State University. USA), Yulia Brockdorf, Rich McClure (Hillsboro, OR, USA), Jeff Krehbiel (Krehbiels Specialty Meats; McPherson, KS, USA), Stan Barenberg, Samantha Potts (Longneck Ranch; Rose Hill, KS, USA), Ricky-Lee Erickson, Kylea Clarke (Melbourne Museum - Museums Victoria; Melbourne, VIC, AU), Jay Villemarette, Michelle Hayer (Museum of Osteology; Oklahoma City, OK, USA), Hein Van Grouw, Mark Adams, Paul Kitching. Joanne Cooper, Judith White, Pete Key, Claire Walsh (Natural History Museum; Tring, UK), Lawrence Witmer (Ohio University Vertebrate Collection; Athens, OH, USA), Eddie Witte, Rebecca Snyder, Jennifer D’Agostino (Oklahoma City Zoo, Oklahoma City, OK, USA), Ashley Bowen, Kathy Wolyn, Katie Glatfelter (Pueblo Zoo; Pueblo, CO, USA), Heather Janetzki, Kristen Spring, Alison Douglas (Queensland Museum; Brisbane, QLD, AU), John De Campo (Queensland Parks and Wildlife Service and Partnerships; Cairns, QLD, AU), Scott Newland, Heather Arens, Phillip Horvey (Sedgwick County Zoo; Wichita, KS, USA), Joylene Reavis (Sugar Maple Emus; Monroe, WI, USA), Josef Lindholm, Richard Kotarsky, Tom Mortimer (Tulsa Zoo; Tulsa, OK, USA), University of New England Natural History Museum (Armidale, NSW, AU), Betty Lou Cauffman (Valley View Emus; Fennimore, WI, USA), Steve Sarno, Adam Sarno (Wellington, CO, USA), Terry Carmichael (Wet Tropics Management Authority; Cairns, QLD, AU), and Jean A. Paré, Charlotte Hollinger (Wildlife Conservation Society at Bronx Zoo; Bronx, NY, USA). For believing in me, and always stepping up to assist in my research or foolhardy pursuits when I need them, I am grateful for my close relationships with Nicholas Mahler, Sue Ware, Maria Bailey, Jennifer Campbell-Smith, Tim Carlton, Laura Rosen, and AJ Dodd. For colleagues and mentors that have helped me get to where I am today, and have probably done more for me than they realize, I additionally thank Akinobu Watanabe, Shane Kanatous, Brent Breithaupt, Joseph Sertich, Malcolm Bedell, Louis Taylor, Gregory McDonald, Larry Witmer, Danny Martin, Kirk Johnson, Chris Weege, Ryan Felice, Alan Turner, Peter Larson, Mike Getty, Gregory Erickson, Philip Currie, Mark Norell, Patrick O’Connor, Scott Sampson, Nathan Kley, Amy Balanoff, Gabe Bever, and James Kirkland. I appreciate the assistance in specimen µCT imaging from: Morgan Hill, Andrew Smith (Microscopy and Imaging Facility of the AMNH; New York, NY, USA), Steven Rigsby (Dentsply Research and Development Office; Tulsa, OK, USA), Manon Wilson, Claire Terhune, Lyndon Colvin (MicroCT Imaging Consortium for Research and Outreach; Fayetteville, AR, USA), and Ryan Ridgely (Ohio University MicroCT Scanning Facility; Athens, OH, USA). The author also thanks Jeremy Delcambre, Robert Lee (Colorado State University; Fort Collins, CO, USA) for their kind use of dissection and processing facilities. Research funding and conference travel assistance for this study was provided by the following organizations: National Science Foundation (1450850, 1457180, 1725925, & 1754659; to P. M. G.), Oklahoma State University Center for Health Sciences (Department of Anatomy and Cell Biology, Graduate and Professional Student Government Association Travel Reimbursement), Western Interior Paleontological Society (Karl Hirsh Memorial Grants; to T. L. G.), The Company of Biologists and iv Acknowledgements reflect the views of the author and are not endorsed by committee members or Oklahoma State University. sponsoring journal, Experimental Biology (Visiting Fellowship, JEBTF1903122; to T. L. G.), American Association for Anatomy (Visiting Scholarship, travel awards; to T. L. G.), Society of Vertebrate Paleontology (Jackson School of Geosciences Travel Grant; to T. L. G.), Society of Integrative and Comparative Biology (Charlotte Mangum Student Support Travel Awards; to T. L. G.), and American Emu Association (Travel Assistance; to T. L. G.). v Acknowledgements reflect the views of the author and are not endorsed by committee members or Oklahoma State University. Name: TODD LANDON GREEN Date of Degree: DECEMBER, 2020 Title of Study: ONTOGENY, DISPARITY, AND FUNCTION OF THE ENIGMATIC CASQUES OF CASSOWARIES (CASUARIUS): A CASE STUDY OF CRANIAL ORNAMENTATION IN ARCHOSAURS Major Field: BIOMEDICAL SCIENCES Abstract: Modern cassowaries (Casuarius spp.) are flightless birds best known for their elaborate cranial casques, keratin and bone headgear located above the orbit and neurocranium. Because cassowaries are rare, seclusive, and potentially dangerous, there have been few in-depth studies regarding headgear biology despite functional speculations and suggestions of the casque as a modern analog for the ornaments of extinct taxa, which they resemble. Without baseline anatomical, ontogenetic, disparity, and functional studies, the casque’s position in comparative and evolutionary studies remains uncertain. I address this uncertainty by elucidating the biological role(s) of the casque through micro-computed tomography imaging (µCT), evaluation of allometric scaling, two-dimensional shape analyses, and testing for similarities and differences in the comparative anatomy of osseous headgear across extant and extinct casqued archosaurs. I find that southern cassowary (C. casuarius) casques are comprised of eight distinct cranial bones and are far more complex than previously realized. Additionally, the central, dorsal element appears to be neomorphic and unique to cassowaries. The keratinous and osseous portions of C. casuarius casques scale with strong positive allometry, reaching the majority of their maximum size by sexual maturity. Casques of C. casuarius do not appear to be sexually dimorphic in ontogenetic trajectory nor adult shape. However, I find that casque shape may differ between certain C. casuarius regional populations and that casques are shaped significantly differently between