Temnospondyl amphibians experienced a geologically brief interval of success in the wake of the end-Permian mass extinction. This study examines the relationship between taxonomic and ecological diversity of temnospondyls across the Permian-Triassic boundary in the Karoo Basin of South Africa. Ecomorphological diversity, as implied by differences in cranial shape, was incorporated into the study by the use of a landmark-based geometric morphometric analysis.Both taxonomic diversity and cranial disparity are low during the Permian and increase across the Permian-Triassic boundary. Taxonomic diversity is stable through the Triassic, but disparity shows subsequent increases during the Olenekian and Anisian. Temnospondyls are restricted in size immediately following the extinction, but size range fully rebounds by the Olenekian. Cranial shape is heavily influenced by phylogenetic relatedness, and the observed increases in disparity may be partly the result of decreases in the net relatedness of coeval Karoo stereospondylomorph temnospondyls in younger faunas. The increase in community level taxonomic diversity for temnospondyls in the Karoo following the end-Permian mass extinction was likely facilitated by an influx of distantly related and ecologically distinct species. K E Y W O R D S end-Permian mass extinction, geometric morphometrics, morphological disparity, recovery, Stereospondyli

Recovery of marine biodiversity following the Permo-Triassic extinction is thought to have been delayed relative to other mass extinctions. Terrestrial vertebrate biodiversity is said to have taken as much as 15 Myr longer to recover than the marine. The present study tests, at the scale of an individual fossil community, whether a disparity in biodiversity existed in the American Southwest, between the Moenkopi Formation, containing an early Middle Triassic (Anisian) terrestrial tetrapod fauna, and the Chinle Formation, containing a successor Late Triassic (Norian) tetrapod fauna. Taking Chinle faunal biodiversity to represent full biotic recovery, comparison of taxonomic and guild diversity of faunas from similar depositional and taphonomic environments in these two formations allowed us to assess the possibility of incipient terrestrial recovery of biodiversity in the Anisian.Comparisons were made between the Holbrook Member fauna of the Moenkopi, a unit best characterized as a low-sinuosity medium- to coarse-grained fluvial deposit, and each of four Chinle stratigraphic units, representing fluvial settings from sandy low-sinuosity to muddy high-sinuosity. Three metrics were applied: generic and familial taxonomic diversity and guild diversity; these were compared by rarefaction. Simpson and Shannon diversity metrics augmented the analysis. Units of extraordinary preservation in the Chinle—the so-called blue layers—were removed from the analysis. In all tests the biodiversity of the Holbrook Member fauna is within the variation seen in Chinle faunas.If the results of our study represent global conditions, they suggest that by at least early Anisian time (∼6 Myr after the P/T extinction) biodiversity had reached levels comparable to those seen in the Late Triassic. This potentially brings the terrestrial vertebrate recovery in line with the 4–8 Myr it took for recovery in the marine realm.

Thesis Supervisor: Professor Christopher A. Brochu Copyright by DAVID A TARAILO 2018 All Rights Reserved ii ACKNOWLEDGEMENTS My first expression of thanks must go to Chris Brochu for taking me on as a student, and for the support and advice he has offered me during my time at the University of Iowa. Without his generosity and guidance this dissertation would not have been possible. I am also indebted to the other members of the Brochu lab group, the Brochuchidae, for their help and support over the years. Special thanks go to Adam Cossette, who found himself in the same boat as me during this doctoral adventure, and to Amanda Adams, in whom I have found a companion for graduate school and beyond. I am also thankful to all of the other members of my defense committee: expressed great patience with my efforts to schedule my defense. I hope that my dissertation, and the defense I gave of it, earned me their confidence that I have earned this honor. The Department of Earth and Environmental Sciences provided me with funding for my entire tenure at the University of Iowa, a fact for which I am eternally grateful. Several staff and faculty members in the department deserve special mention, and these include Christine Harms, Angela Bellew, Tiffany Adrain, and Hallie Sims. This dissertation comes as the result o f a lifetime of interest in prehistoric life, and this was only possible because of the support both my parents gave me in my young fascination with dinosaurs and learning in general. I have been lucky to have a loving family on whose support I knew I could always rely. To each end every one of my family members I want to extend my deepest possible expression of gratitude. My dear friend Heather, who I think of as a member of my family, and who has been a positive iii influence on me for more than half my life, deserves her own special acknowledgement. Heather was there for me during some of the most difficult times of my life, and it I fear this degree would never have been possible without her help. I wish to acknowledge the paleontologist fellows I have met over the course of my professional journey. Sandy Carlson has been an enthusiastic and eager mentor since my time at UC-Davis. David Fastovsky made sure my head was on straight, and set me on a good and fruitful path while I was at URI. Dan Chure was a good friend as well a supervisor while I worked at DNM. All of the creators of dinosaur-themed art, merchandise, and entertainment that fueld my obsession as a child deserve a hearty thanks. Forefront in this enormous list (that could go on for pages) include Ray Harryhausen, Abstract The latest-Permian mass extinction was the greatest biotic crisis of the Phanerozoic. The extinction decimated both marine and terrestrial communities, and changed the evolutionary trajectory of multicellular life on the planet. The unique nature of the extinction's aftermath has prompted attention from paleontologists seeking to understand the timing and pattern of the Triassic recovery. With this dissertation I have sought to ...