IDENTIFICATION AND IMPLICATIONS OF A COLONIAL RUGOSE CORAL IN THE LATE ORDOVICIAN KOPE FORMATION

The Kope Formation is Upper Cincinnatian (Late Ordovician) and occurs in southwest Ohio, northern Kentucky, and southeastern Indiana. This formation represents a progradational sequence that varies in thickness between 200-260 feet and is comprised of prominent shales interbedded with minor calcareous limestones. The formation is commonly identified by the presence of brachiopods, bryozoan, trilobites, echinoderms, and other benthic invertebrates. Based on the lithology and faunal composition, the Kope Formation represents a distal off shore environment below most normal storms.

Corals are notably absent in the Kope fossil assemblage, which is expected given the depth and amount of clastic sedimentation. However, a large colonial rugose was recently discovered in the Kope Formation of Northern Kentucky. Unfortunately, the slab containing the coral was discovered as float partially buried beneath several inches of sediment. The preservation on the slab was highly variable, with broken and abraded fossil on the top surface as well as an articulated partial asteroid on the lower surface. The slab contains abundant Sowerbyella rugose, a brachiopod which is diagnostic of the formation, indicating the coral is endemic to the Kope. The coral is approximately 5.5 inches in length and 4.0 inches wide and composed of corallites ranging from 3-5mm in diameter with between 10-14 major septa. This is consistent with Cyathophylloides cf. C. burksae, a coral known from the shallower and younger Whitewater Formation following the Richmondian invasion.

The discovery of this coral within the Kope Formation raises questions regarding the timing and nature of the Richmondian invasion. In particular, biogeographic pathways may have been open earlier for the rare migration of planktonic larva. However, the full invasion of Richmondian taxa didn’t occur until either the dispersal events became more common, or the basin became more favorable to the invaders’ environmental preferences.