The knotty pebblesnail,

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Somatogyrus constrictus'', of minute

freshwater snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

s with an operculum, aquatic

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc 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 esti ...

s or

micromollusc A micromollusk is a shelled mollusk which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine mollusks, although in addition, numerous species of land snails and freshwater mollusks also r ...

s in the family

Lithoglyphidae Lithoglyphidae is a family of small freshwater snails with gills and an operculum, aquatic gastropod mollusks. This family is in the superfamily Truncatelloidea and in the clade Littorinimorpha (according to the taxonomy of the Gastropoda by ...

. This species is endemic to Alabama in the United States. Its natural habitat is the

Coosa River The Coosa River is a tributary of the Alabama River in the U.S. states of Alabama and Georgia. The river is about long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed April 27, 2011 ...

. Although the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

officially categorises the species as

Data Deficient A data deficient (DD) species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as offering insufficient information for a proper assessment of conservation status to be made. This does not necessaril ...

, it also considers it as ''

Possibly extinct The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biologi ...

'', as it has not been recorded since the river was impounded. This latter classification is also supported by The Nature Conservancy. The taxonomic validity of this species has been questioned; it may represent morphological aberrations of other, valid species. If it is a valid species, it would be assessed as threatened.

References

Endemic molluscs of the United States Somatogyrus Freshwater snails Gastropods described in 1904 Taxonomy articles created by Polbot Endemic fauna of Alabama {{Lithoglyphidae-stub