EARLY PERMIAN MARINE VERTEBRATE COMMUNITIES OF THE NORTH AMERICAN GREAT PLAINS

While freshwater, estuarine, and terrestrial vertebrate ecosystems are well known from the Lower Permian rocks of the United States and elsewhere, similarly-aged marine sites featuring any number of vertebrate taxa are scarce in the global fossil record. Studies of the Permian in the Ural Mountains, Peruvian Andes, and Northeast Kansas, originally suggest that marine communities from this time featured large grazing elasmobranchs and small bony fishes living on a typical Paleozoic carbonate reef ecosystem. This in turn supported a food chain featuring medium sized piscivorous Elasmobranchs and large predatory Eugeneodont Holocephalians. Our work over the last three years in Texas and Kansas has shed light on a different type of community: one with crushing (hybodont) sharks, grazing Holocephalians, large predatory bony fishes, and Ctenacanthiform sharks serving as apex predators in much of the Permian Basin. The invertebrates supporting this community varied wildly in space and time, but fossils from above the Carboniferous-Permian Boundary of Texas suggest that one dominant feature of this ecosystem, the Hybodont sharks, were in place in Texas’ Permian Basin at the very start of Permian deposition. Comparison of these sites to other marine vertebrate bearing Permian sites in Texas, Kansas, and Oklahoma has also helped to shed light on the varied paleoecologies of the Hybodonts, Ctenacanths, and Eugeneodonts of the entire Permian Seaway of the central United States, and provide a useful point of comparison for a better global consensus on marine vertebrate ecosystems of this time.