2.2" Ordovician "Gastropod" (Pterotheca) Fossil - Wisconsin
This is a 2.2" wide example of the Middle Ordovician "gastropod", Pterotheca attenuata. These fossils have been classified as monoplacophoran, bellerophont, or as another type of gastropod due to its unusual morphology. This specimen is part of an old collection from the Grand Detour Formation in Rock County, Wisconsin. It has been partially exposed from the rock it was found in.
Gastropods, which are more commonly referred to as snails, have been around since the Late Cambrian period. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. There are 611 known families of gastropods, of which 202 families are extinct and appear only in the fossil record.