DIVERSITY OF PALEOZOIC NON-AMNIOTE TETRAPOD FAUNAS

Peak diversities of non-amniote tetrapods occur during the later Pennsylvanian through the mid-Permian, spanning roughly 30 million years. Faunal assemblages for most of the Paleozoic are rare and are almost completely absent for roughly 30 million years from the end of the Devonian until the mid-Mississippian. Most Paleozoic non-amniote faunas typically represent deposition in fresh- to brackish-water pond and swamp settings located in present day North America and Europe. Faunal data from nine non-amniote faunas (Delta, Iowa; East Kirkton, Scotland; Joggins, Nova Scotia; Newsham, Northumberland; Nyrany, Czechoslovakia; Linton, Ohio; Waurika, Oklahoma; Geraldine, Texas; and Orlando, Oklahoma) were subjected to rareifaction, producing diversity curves with which comparisons of the various faunas were made. Mississippian faunas show lower diversity than either Pennsylvanian or Permian faunas, while diversity curves for Pennsylvanian faunas are much higher than either Mississippian or Permian faunas. The diversity peaks for the Pennsylvanian faunas, in particular Linton and Nyrany, coincide with family level diversity peaks for all three orders of lepospondyls. Examination of faunal lists for the nine localities show that Linton, Nyrany, and Joggins have greater numbers of lepospondyl taxa than any of the other faunas, while the number of taxa from other orders is roughly similar between localities. Faunal comparisons based upon the depositional environment of the localities indicate that diversity levels are not consistent through time. Lake faunas (Nyrany, Linton, Newsham, Waurika, Orlando, and Delta) show high levels of variation in diversity during the Paleozoic. In contrast the curves for East Kirkton and Joggins, the two terrestrial deposits, show similar trajectories. The in trajectory stability between terrestrial and fresh-water deposits are likely attributable to variation in depositional setting among the fresh-water faunas.