''Quadrula'' is a genus of

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

s, aquatic

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is es ...

s in the family

Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is at its most dive ...

native to rivers of the

American Midwest The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of ...

and mid-south. All have thick

nacreous Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre i ...

shells with well-developed

hinge teeth Hinge teeth are part of the anatomical structure of the inner surface of a bivalve shell, i.e. the shell of a bivalve mollusk. Bivalves by definition have two valves, which are joined together by a strong and flexible ligament situated on the hin ...

, many also with external shell sculpturing of nodules or lumps.

Species within the genus ''Quadrula''

In 2012, many species classified as ''Quadrula'' were moved to '' Rotundaria'' and ''

Theliderma ''Theliderma'' is a genus of freshwater mussels, aquatic bivalve mollusks in the family Unionidae. They are native to North America. This genus is sometimes classified in an expanded ''Quadrula''. Species within the genus ''Theliderma'' Note: ...

'' based on genetic and morphological evidence. Species currently in ''Quadrula'' now consist of:''Quadrula'' World Register of Marine Species
/ref> * '' Quadrula apiculata'' (Southern mapleleaf) * '' Quadrula fragosa'' (Winged mapleleaf) * '' Quadrula nobilis'' (Gulf mapleleaf) * '' Quadrula quadrula'' (Mapleleaf) * '' Quadrula rumphiana'' (Ridged mapleleaf) * '' Quadrula verrucosa'' (Pistolgrip)

References

Bivalve genera Molluscs of the United States Taxonomy articles created by Polbot {{Unionidae-stub