The Scaleshell Mussel (Potamilus leptodon) is a species of freshwater mussel currently found in Arkansas, Illinois, Missouri, Oklahoma, and South Dakota. It is considered extirpated from an additional seven states. The Scaleshell Mussel is a small, thin-shelled mussel that inhabits medium to large rivers with stable riffles and river bottoms with sand and gravel where the mussels can burrow. Threats to the species include water quality degradation, sedimentation, channel destabilization and habitat destruction.