Two Exceptional Echinoderm Occurrences from the Cincinnatian (Katian, Late Ordovician) of Maysville, Kentucky, USA

Abstract

Record ID: 26

Award(s): Excellence in Research Mentoring; Excellence in Research Communication

Student Major: Geology; Paleontology

Project Advisor: Carlton Brett

Abstract: Echinoderms dissolve quickly after death; therefore, their fossils are generally considered rare. However, Late Ordovician rocks exposed by the Cincinnati Arch have yielded many excellent examples of echinoderms suddenly buried alive en masse and preserved beautifully. Here we describe two new occurrences of such exceptional echinoderm preservation, both from the Grant Lake Formation. At one outcrop, a layer preserves a fascinating community including hundreds of Cincinnati's City Fossil, Isorophus cincinnatiensis, and another outcrop nearby contains multiple echinoderm bearing layers preserving crinoids, edrioasteroids, and one interval containing a shocking twenty-six individuals of cyclocystoids, which are usually incredibly rare, especially in numbers greater than one. This study considers echinoderm population dynamics, intraspecies and interspecies competition, paleoecology, and taphonomy to rebuild a picture of Cincinnati 450 million years ago: near the Equator, sub-tropical, teeming with fascinating communities populated by echinoderms that have been extinct for hundreds of millions of years, and regularly attacked by severe tropical storms. These storms triggered mudslides that moved vast amounts of entombing sediment across the seafloor, rapidly smothering anything in its path. But in turn, these obrution deposits contain some of the most beautiful echinoderm fossils found, and the relative regularity of these occurrences in the tristate area including Cincinnati further emphasizes its paleontological, geological, and natural importance.