''Cyclonaias pustulosa'', the pimpleback, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

freshwater mussel Freshwater bivalves are molluscs of the order Bivalvia that inhabit freshwater ecosystems. They are one of the two main groups of freshwater molluscs, along with freshwater snails. The majority of bivalve molluscs are saltwater species that l ...

, an aquatic

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the family

Unionidae The Unionidae are a Family (biology), 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 a ...

, the river mussels. This species is native to North America, where it is widespread and common. It has possibly been

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

from

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

, however, and populations in Pennsylvania are critically imperiled, according to

NatureServe NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, United States, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and ...

. The species was formerly classified within the genus ''

Quadrula ''Quadrula'' is a genus of freshwater mussels, Aquatic animal, 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 wit ...

'', and in 2012 it was moved to ''Rotundaria'' based on genetic evidence.

References

*Williams, J. D.; Bogan, A. E.; Garner, J. T. (2008). Freshwater mussels of Alabama and the Mobile Basin in Georgia, Mississippi and Tennessee. University of Alabama Press, Tuscaloosa. 908 pp. Unionidae Molluscs of North America Fauna of the Great Lakes region (North America) Fauna of the Southeastern United States Bivalves described in 1831 {{Unionidae-stub