1.9" Ordovician, Cephalopod (Allumettoceras) Fossil - Wisconsin

This is a 1.9" long example of Allumettoceras planodorsatum. This fossil is part of a collection from the Grand Detour Formation in Rock County, Wisconsin. Allumettoceras was an oncoceran, a curve-shelled nautiloid cephalopod. This specimen is a partial shell found embedded in stone.