''Medionidus parvulus'', the Coosa moccasinshell, is a rare

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 ...

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 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 ...

is native to

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

and

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

in the United States, and has 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 the state of

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

.''Medionidus parvulus''.
The Nature Conservancy. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

of the United States.USFWS
Endangered status for eight freshwater mussels and threatened status for three freshwater mussels in the Mobile River Drainage.
''Federal Register'' March 17, 1993. This mussel is up to 4 centimeters long or occasionally larger and has a thin, fragile, dark brown or yellow-brown shell. The

nacre 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 is ...

of the shell is blue, sometimes with pink areas. This mussel is native to the

Mobile River The Mobile River is located in southern Alabama in the United States. Formed out of the confluence of the Tombigbee and Alabama rivers, the approximately river drains an area of of Alabama, with a watershed extending into Mississippi, Georg ...

drainage, where it was once sporadic but widespread. This species is rare except in

Polk County, Tennessee Polk County is a county located in the southeastern corner of the U.S. state of Tennessee. As of the 2020 United States census, its population was 17,544. Its county seat is Benton. The county was created on November 28, 1839, from parts of ...

, where it is locally common in the

Conasauga River The Conasauga River is a river that runs through southeast Tennessee and northwest Georgia. The Conasauga River is longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed April 27, 2011 an ...

. It can also be found in the tributary Holly Creek, which extends into Georgia. It is in severe decline, having been extirpated from much of the

Coosa River The Coosa River is a tributary of the Alabama River in the U.S. states of Alabama and Georgia (U.S. state), Georgia. The river is about long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, ac ...

system and all of the waterways in Alabama where it once occurred.

References

Natural history of Tennessee Natural history of Georgia (U.S. state) parvulus Bivalves described in 1860 ESA endangered species Taxonomy articles created by Polbot {{Unionidae-stub