This Specimen has been sold.
2" Ordovician, Oncoceratid (Tripteroceras) Fossil - Wisconsin
This is a 2" long example of a Middle Ordovician fossil Oncoceratid (Tripteroceras planoconvexum) from Wisconsin. This fossil is part of an old collection from the Grand Detour Formation in Rock County.
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.