Crinoids from the Glen Dean Limestone (Middle Chester) of Southern Indiana and Kentucky

Abstract

Twenty-three species and eight nomina aperta of crinoids from the Glen Dean Limestone (middle Chester) are assigned to the genera Agassizocrinus Owen & Shumard, Aphelecrinus Kirk, Eupachycrinus Meek & Worthen, Hypselocrinus Kirk, Onychocrinus Lyon & Casseday, Phacelocrinus Kirk, Phanocrinus Kirk, Pterotocrinus Lyon & Casseday, Tholocrinus Kirk, and Zeacrinites Troost. The genus Hypselocrinus, represented in this fauna by the new species H. campanulus, has not hitherto been recorded from rocks of Chester (late Mississippian) age. Nine other species described herein have not been recognized formerly from the Glen Dean. Seventeen collecting sites in Indiana and six in Kentucky yielded the material forming the basis of this study. As reported by previous workers, Pterotocrinus wing plates are most valuable for identifying the Glen Dean Limestone, and their distinctive morphology permits them to be recognized and used for this purpose by stratigraphers in the field. Thirteen of the twenty -three collecting localities furnished wing plates of P. acutus Wetherby, P. bifurcatus Wetherby, P. depressus Lyon & Casseday, P. spatulatus Wetherby, or P. vannus Sutton. Future collecting may also indicate the stratigraphic usefulness of two described but unnamed types of Pterotocrinus wing plates. Glen Dean crinoids probably were most abundant in clear agitated water and are best preserved on the upper surfaces of limestones covered by shales or in calcareous shales formed under quieter water conditions. Most of the material studied came from interbedded limestone, sandstone, and shale in the upper part of the Glen Dean2 and is associated with an abundant and diverse marine fauna.