The proposed study involves both a detailed systematic revision of the crinoids from the late Osagean (Mississippian) Keokuk Limestone and the basal part of the Warsaw Formation in Iowa, Illinois, and Missouri, and a study of their depositional settings. Crinoids from the Keokuk and basal Warsaw have not received study in the latter half of this century, despite the fact that crinoids of this age in other areas are well understood, and these faunas are from the North American Standard Section of the Mississippian. Re.evaluation of these faunas will complete our understanding of the systematics, community paleoecology, and depositional occurrences of crinoid faunas from the late Osagean throughout the east.central United States. This in turn will enable us to interpret the constraints and controlling factors that were responsible for the distribution of late Osagean crinoids. We will test these new data against the environmental controls model, which is based on multivariate analysis of late Osagean crinoid faunas from the Borden deltaic complex in Indiana and Kentucky. Documentation of controlling factors operating on late Osagean crinoids is essential for a fundamental understanding of Paleozoic crinoids. The Osagean was witness to the maximum diversity known among crinoids, and yet at the close of the Osagean, crinoids suffered extreme extinction. Crinoid faunas after the terminal Osagean extinction were very different in taxonomic character and remained basically the same from the recovery following the extinction event until the terminal Paleozoic mass extinction. Results from the proposed study are prerequisite for posing larger questions on the evolution of Paleozoic crinoids.
