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HARPER-DISSERTATION-2019.Pdf CRANIODENTAL ADAPTATION AND HOMOPLASY IN EARLY MAMMALS by Anthony Maxwell Harper A dissertation submitted to Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland September, 2019 Abstract For the first two-thirds of their over 180-million-year history, mammals left a sparse fossil record. Often the only direct evidence of these early forms are small and unassociated craniodental fragments. Despite these limitations, the three chapters of this thesis support the effectiveness of this type of material for estimating the functional and autecological capacities in Mesozoic mammals, through high resolution imaging and morphometric analysis of the molariform dentition. Each of the three chapters is a self-contained study addressing separate topics relating to the evolution of dental and petrosal morphology. The common thread between all sections is that variation in craniodental structure among Mesozoic lineages is greater than would be expected based only on the disparity seen among extant small mammals. This is a result of both the more “modern” dynamics of dental evolution in more Mesozoic mammalian lineages than historically appreciated (Chapters 1 and 3), and the more “primitive” morphology of the inner ear, even in groups very closely related to extant crown therians (Chapter 2). In both cases, the craniodental morphologies described are outside the range of variation seen in extant species. Chapter 1 describes several new specimens from the herbivorous stem-therian mammal Reigitherium, from the Late Cretaceous of Patagonia. These newly available specimens demonstrate that the herbivorous molar morphology seen in Reigitherium is ii derived from the more plesiomorphic tuberculosectorial pattern seen in the South American endemic group Meridiolestida. Chapter 2 presents descriptions and analysis of the internal structure of three stem therian petrosal bones from the Late Jurassic of North America, and middle Cretaceous of Mongolia. Within the comparative context of labyrinthine endocast evolution, it can be determined that many of the advanced features of modern therian hearing likely developed only after their divergence from their common ancestor with the fossil groups described here. Finally, Chapter 3 presents a macroevolutionary analysis of lower molariform shape change across a large sample of early mammaliaforms, using high-level morphometric methods. The results of this analysis suggest that the stochastic processes controlling the shape evolution of lower molariforms in crown Mammalia are shared across a wide range of “triconodont”, “symmetrodont”, and “tribosphenic” Mesozoic taxa. Dissertation Adviser Gabriel S. Bever Dissertation Readers Guillermo W. Rougier Brian M. Davis Adam D. Sylvester iii When I lay asleep, then did a sheep eat at the ivy-wreath on my head—it ate, and said thereby: “Zarathustra is no longer a scholar.” It said this, and went away clumsily and proudly. A child told it to me. I like to lie here where the children play, beside the ruined wall, among thistles and red poppies. A scholar am I still to the children, and also to the thistles and red poppies. Innocent are they, even in their wickedness. But to the sheep I am no longer a scholar: so willeth my lot—blessings upon it! F. Nietzsche Thus Spoke Zarathustra: Chapter 38 – On Scholars iv Acknowledgments Even during the darkest times in my academic and professional career, I have had the incredible good fortune of being able to look up toward several brilliant constellations. In the paleontological sphere these stars include the amazing people at the Los Angeles County Museums, especially Xiaoming Wang, Luis Chiappe, and Shelly Cox, who gave me my start as a volunteer in VP. I am also thankful for the kindness and patience shown by my supervisors Mark Roeder, Bruce Lander (both at Paleoenvironmental Associates), and Aaron Kaye (Badlands National Park) during my first part-time jobs in this field. Since joining the JHU anatomy program it has been an amazing experience contributing to three field seasons in the Big Horn Basin of Wyoming with Amy Chew, Shawn Zack, and Tonya Penkrot. And I will also fondly remember driving across central Patagonia looking for huesitos with Leandro Canessa, Andy Lires, Willy Turrazini, and Luca Appella-Guiscafre. Gracias por aguantarme. I have also been embarrassingly fortunate to have accumulated such an immense number of other friends, teachers and inspirations in paleontology, without whom this dissertation would have been impossible. Topping this list are Don Prothero, Michael Novacek, Rich Cifelli, ZheXi Luo, Annalisa Berta, Brian Davis, John Wible, Gabriel Bever, Eric Ekdale, David Weishampel, Cara Burres-Jones, Beth Strassler, Kena Fox-Dobbs, Paul Koch, Greg Wilson, Aneila Hogan, Yue Zhang, and Jessica Martin. To these folks I apologize for not knowing not to express how much your hard work and kindness has meant to me in this project, short of quoting G. G. Simpson the most prominent paleomammalologist, who in recommending his field to introverts like me wrote: “one of v the great values of paleontology is that it enables us to live in our own complex minds not just a few score years but more than three billion years.”1 Thank you for making those years so memorable. Above all, I am grateful for the direction provided by the brightest stars in my graduate career - David Archibald, Ken Rose, and Guillermo Rougier. It’s been a long strange trip. Thank you. I also want to thank all my friends and teachers in the Earth sciences, starting especially with David Douglass, Bruce Carter, Ling O’Connor, and Gerry Lewis, at Pasadena City College’s Geology Department, and the PCC Dana Club. As an undergraduate at UC Santa Cruz it was also a lot of fun taking part in several geology classes, and the 2007 Summer field season in the Inyo/White Mountains, thanks to the impressive organizational capabilities of Hide Schwatrz, Casey Moore, and Chris Pluhar (currently at Fresno State). I am also grateful to Gary Girty (SDSU), Ben Passey, and Naomi Levin (both currently at University of Michigan) for letting me into their exceptional graduate courses, and for allowing me to work on various non sequitur projects. Outside of the classroom, I am also extremely lucky to have received advice and encouragement from Thomas Bown, Judy King (CSU Dominguez Hills), Andy Evans (Geologist at AECOM), and Kimberly “Rain” Miner (Geoscientist at the Army Geospatial Research Lab). Thank you all for providing me with a compass in this strange world. Once this dissertation is finished I hope to see you in the field soon. vi The last decade and a half has also brought me into sympatric association with an amazing variety of biologists. The classes taught by Russell DiFiori (Pasadena City College), Tod Reeder, Marshall Hedin, Ken Burns, Michael Simpson, and Robert Zeller (SDSU) have been amazing experiences, for which I am extremely grateful. As a wildlife biologist at the San Diego Natural History Museum, working with my role models Scott Tremor, Phil Unit, Drew Stokes, Lori Hardgrove, Brad Holingsworth, and Melissa Stepek, has been one of the greatest times of my life. And my former supervisors Punkaj Kapahi (currently at Buck Institute), Viceca Sapin (Caltech), and Sandra Garver (SDSU anatomy), have also been inspirations to me throughout my academic career. Additionally, I have benefited immeasurably from the kindness of Patrick Luckett (JHU), Geoffrey Manley (University of Oldenburg), Steve Gliessman (UC Santa Cruz), Richard Etheridge, Mike Van Patten, Bob Mangan (the last three at SDSU), Phil Rundel (UCLA), Cindy Corbitt (University of Louisville), Samantha Young (Grossmont College), Yvea Moore (Crissy Field), and Isaac Simpson (Halibut for Humanity). Thank you all for making life so interesting. I will also be forever grateful for the expertise and patience that my teachers in the rarified spheres of math and other technical fields have shown me; starting especially with Anna Osipova, my high school math teacher who convinced me to “stick with it.” Likewise, this project would not have been possible without the superhuman commitment towards teaching shown by my graduate statistics professors Doug Deutschman and Matt Edwards at SDSU; and Gary Rosner, Robert Scharpf, Fernando Pineda, Frank Curriero, and Adam Sylvester at JHU. What little illustration skill I have is entirely due to the amazing talents of vii Tim Phelps, Ian Suk, Juan Garcia, and Gary Lees in the Johns Hopkins Art as Applied to Medicine Department; and the fact that this dissertation exists at all is due to Arlene Daniel (JHU Functional Anatomy and Evolution). To the many people I have missed here, please know that I am very sorry that I will never be able to list everyone who has indispensably helped me along my academic and professional trajectory. To everyone who has ever gotten behind me and helped push, thank you. Finally, because the best part of being a mammal is having a mom, I thank first and foremost my mom Lynn, and her mom Mary Ann (“Mimi”). Thank you for letting me pick apart those owl pellets, and everything else. 1In: Laporte, L. 2000. George Gaylord Simpson: Paleontologist and Evolutionist. Columbia University Press viii Publications and Coauthors The material in Chapter 1 is published as: Harper, T., A. Parras, and G. W. Rougier. Reigitherium (Meridiolestida, Mesungulatoidea) an enigmatic Late Cretaceous mammal from Patagonia, Argentina: morphology, affinities, and dental evolution. Journal of Mammalian Evolution (2018). https://doi.org/10.1007/s10914-018-9437-x This work was accomplished with the expert help and advice of the following coauthors: Ana Parras, INCITAP (CONICET-UNLPam), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina Guillermo W. Rougier, Department of Anatomical Sciences and Neurobiology, University of Louisville, 511 S. Floyd St., Louisville, KY 40202, USA In particular, the sections “Study Area and Sample Provenance” and “Geological Background” in Chapter 1 were written by Ana Parras, one of the original discoverers of the Anfiteatro locality.
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