.7" Ordovician Hyolithid (Hyolithes) Fossil - Wisconsin

This is a .7" wide example of Hyolithes baconi, an Ordovician-aged genus of hyolitha. Hyolithids are a member of the Lophotrochozoans, which is the superphyllum containing molluscs, brachiopods, and bivalves. The relationship of hyolithids to these groups is still a mystery. This fossil is part of an old collection from the Grand Detour Formation in Beloit, Wisconsin. It has been exposed from the rock it was found in.