Quadrula

Quadrula is a genus of freshwater mussels, aquatic bivalve mollusks in the family Unionidae native to rivers of the American Midwest and mid-south. All have thick nacreous shells with well-developed hinge teeth, many also with external shell sculpturing of nodules or lumps. In 2012, many species classified as Quadrula were moved to Rotundaria and Theliderma based on genetic and morphological evidence.Species currently in Quadrula now consist of: