''Alvania densecostata'' is an extinct

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), ...

of minute

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

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

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

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Rissoidae Rissoidae is a large family of sea snails. Members of the Rissoidae are very small in size and possess an operculum. Distribution and habitat Rissoidae are found worldwide. They live on sandy or gravel bottoms among algae or marine plants. Th ...

.MolluscaBase eds. (2024). MolluscaBase. Alvania densecostata Harmer, 1920 †. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1027565 on 2024-02-06

Description

The length of the shell attains 3 mm, its diameter 1 mm. (Original description) The solid, minute shell is elongate-turreted. The

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

s are convex. They are ornamented by numerous fine, nearly straight ribs, crowded closely together, intersected by spiral striae which become stronger and more prominent below the periphery.Harmer F. W. (1920-1925). The Pliocene Mollusca of Great Britain, being supplementary to S.V. Wood's monograph of the Crag Mollusca. Vol. 2. Monographs of the Palaeontographical Society. 72(344): 485-652, pl. 45-52 (part 1, December 1920); 73(346): 653-704, pl. 53-56 (part 2, July 1921); 75(352): 705-856, pl. 57-64 (part 3, December 1923); 76(354): i-xiv, 857-900, pl. 65 (part 4, January 1925)
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Distribution

Fossils of this species were found in late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58St. Erth, Cornwall, Great Britain.

References

Gastropods described in 1920 densecostata {{Improve categories, date=February 2024 Prehistoric gastropods Rissoidae stubs