''Extra extra'' or ''Marginella extra'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of minute

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

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 ...

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 e ...

micromollusk 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 ...

in the family

Cystiscidae Cystiscidae is a taxonomic family of minute sea snails, marine gastropod mollusks or micromollusks. Description The shell is minute to large, either white, uniformly colored, or patterned; the surface is smooth, sculptured, or axially costate; ...

. Some malacologists place this genus more simply in the family

Marginellidae Marginellidae, or the margin shells, are a Taxonomy (biology), taxonomic family (biology), family of small, often colorful, sea snails, Marine (ocean), marine gastropod molluscs in the clade Neogastropoda. Taxonomy The higher classification of ...

Taxonomy

''Marginella extra'' was originally described under name ''Extra extra'' by French zoologist

Félix Pierre Jousseaume Félix Pierre Jousseaume (12 April 1835, in Charente-Maritime – 3 November 1921) was a French zoologist and malacologist. He studied medicine in Paris where he then practised. His thesis was ''Des Végétaux parasites de l'Homme''. He participate ...

in 1894. He placed this species to the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus ''Extra'' Jousseaume, 1894. Dautzenberg (1929)Dautzenberg, Ph. (1929). Mollusques testaces marins de Madagascar. Faune des Colonies Françaises, Tome III moved this species into genus ''

Marginella ''Marginella'' is a very large genus of small tropical and temperate sea snails, marine gastropod molluscs in the subfamily Marginellinae of the family Marginellidae, the margin snails. It is the type genus of the family. The shells of species ...

''.

Diagnosis

The

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

is minute, white, semitranslucent; prominent axial costae present;

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

sunken but not immersed; lip strongly thickened, smooth, lacking denticulation, flared posteriorly; siphonal notch absent; posterior notch absent; distinct parietal callus "shield" present; columella multiplicate, with 5 plications plus parietal lirae, plications slightly excavated inside

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

due to parietal callus deposits.

Distribution and habitat

Recorded only from western

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

along

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

, apparently in shallow water.

References

External links

Coovert G. A. & Coovert H. K. (1995). "Revision of the Supraspecific Classification of Marginelliform Gastropods". ''The Nautilus'' 109(2 & 3):43–110
{{Commons category Cystiscidae Gastropods described in 1894