The Jurassic Origins of Mesoeucrocodylia: Taxonomic and Phylogenetic Revision of a Key Mesozoic Reptile Lineage

Crocodyliformes, the reptile group including crocodiles, alligators, and their extinct relatives is a key vertebrate lineage that originated approximately 230 million years ago. There are fewer than 30 living crocodyliform species surviving today and all are semi-aquatic ambush predators. However, the extinct relatives of modern alligators and crocodiles were incredibly diverse during the Cretaceous period (~145-66 million years ago) with body sizes, shapes, and habitat preferences rivaling modern mammals. Crocodyliforms were apex predators on land in the southern hemisphere, acquired their modern semi-aquatic ambush ecology multiple times, evolved to have generalist and even plant-eating diets, and even became some of the largest most dominant sea-going predators. This project will focus on understanding this spectacular radiation of reptiles by delving into the its evolutionary roots in the Jurassic Period, 100 million years earlier. The investigators will examine fossil specimens in museum collections around the world, as well as the skeletons of modern species, to assemble a comprehensive, precise history of crocodyliform origins. The researchers will use these data to reconstruct the crocodyliform family tree and redescribe and illustrate key Jurassic specimens based on first hand observation and high-resolution x-ray CT imaging, allowing the researchers to view previously unknown internal features that will help clarify their evolutionary relationships. The outcome of this project will an unprecedented reconstruction the crocodyliform tree of life, illuminating their evolution during the “Crocodyliform Dark Age” of the Jurassic. The researchers will apply cutting-edge biogeographic models and methods incorporating information from continental fragmentation and climate to test how and where these groups moved across the globe over broad time scales. These novel approaches will allow for a comprehensive look at abiotic continent-scale changes and their biotic effects on skeletal adaptation as well as rate and mode of evolution. The project will generate a massive amount of phenotypic and phylogenetic data that will be made freely available to the research community via open access NSF-funded distribution platforms such as MorphoBank and MorphoSource. The project will contribute to the training of the next generation of paleontologists by supporting PhD and postdoctoral researchers. Moreover, the robust morphological phylogeny, constructed using the latest phylogenetic methods, will provide a framework for future work on archosaur evolution. The innovative techniques and widely applicable conclusions from this research will promote interdisciplinary work among paleontologists, ecologists, and evolutionary biologists. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.