COMPARISON OF LATE PALEOZOIC ICE AGE TETRAPODS, PALEOENVIRONMENT, AND PRESERVATION BETWEEN EASTERN AND WESTERN PANGEA

Earth's climate history throughout the Phanerozoic is dominated by global greenhouse conditions. Only rarely do we have fully icehouse worlds such as today and during the Late Paleozoic. Considerably less is known about the global and local effects of the Late Paleozoic ice age due to its position in deep time and debates on the Pangean supercontinent’s paleogeography. The global trend in climate displays a shift from wet to dry as the equatorial coal swamps collapsed, and an expansion of drier ecosystems within the continental interior. The shift in the predominant ecosystems allowed for a radiation of dry adapted flora and fauna within Western Pangea, with wetter taxa being restricted to the less expansive wetlands. Numerous early synapsids, diapsids, and dry adapted amphibians occupied these new terrestrial habitats. In contrast, Eastern Pangea differs in having an underrepresented tetrapod fossil record and a climate regime at odds with the global trend. To assess whether this is a taphonomic issue, ~100 paleosol samples were collected from sedimentary outcrops of the Dunkard Group exposed near Coolville, Ohio. These samples were studied by using diffuse reflectance spectroscopy, magnetic susceptibility, and anhysteretic remanent magnetization to reveal information on redox conditions that may have affected bone preservation. Our results demonstrate that increased magnetism and decreased concentrations of hematite are associated with samples collected from distal levee and some proximal floodplain environments. This may have been conducive for the preservation of large synapsids like Edaphosaurus and the small amphibian Cacops. However, the data also suggest the paleoclimate may have been too wet to accommodate these taxa. In combination, the data generated by this study provide new insights into Late Paleozoic terrestrial environments, tetrapod evolution, and paleoclimates.