3.4" Ordovician Oncoceratid (Richardsonoceras) Fossil - Wisconsin

This is a 3.4" long (straightline) example of Richardsonoceras simplex, an Oncoceratid (Nautiloidea) from the Middle-Upper Ordovician of Wisconsin. This fossil is part of an old collection from the Grand Detour Formation in Rock County, Wisconsin. Oncoceratids are curved nautiloid cephalopods that have been identified from the Middle Ordovician, up to Late Silurian. Richardsonoceras is known for having a stronger convex curvature than other cephalopods in the family Oncoceratidae.

There is a repaired crack through this specimen.