''Marginellona gigas'' 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 very large deepwater

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 ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Marginellidae. This species was originally thought to be a volute, in the family Volutidae, but it is in fact a giant marginellid.Rosenberg, G. (2012). Marginellona gigas. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=473905 on 2012-06-27 This is the only known species in the genus ''Marginellona'', in other words, ''Marginellona'' is a monotypic genus.

Snail description

The shell can be as large 157 mm. It is thin, translucent, porcellaneous, and narrowly ovate in shape. The

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...

consists of 2-2½ rapidly expanding (diameter 0.5 mm to 11.5 mm in 2 whorls), smooth, conical, glassy whorls, deflected from coiling axis of teleconch by up to 15°. The transition to teleconch is abrupt, marked by a growth line, and accompanied by the formation of thin parietal callus. The teleoconch has up to 3 smooth, inflated, convex, rapidly descending whorls. The suture has abutting whorls. The shell surface is smooth, glazed, and lacking spiral and axial sculpture. The

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 ...

is ovate, narrow posteriorly, broad anteriorly. The outer lip is smooth. The inner lip is smooth, with thin, whitish inductural overglaze in some specimens. The columella has a single sharp, axially-oriented columellar

fold Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure *Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Above ...

and a sharp siphonal fold of nearly equal magnitude. The outer shell surface is uniformly tan to greenish-tan; the aperture is darker brown.

Type locality

West of Sombrero Channel, Nicobar Islands, Indian Ocean, 07°48'N, 92°07'E, in 805 m, coarse sand.

Distribution

This species has been collected in the eastern

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 ...

(

Nicobar Islands The Nicobar Islands are an archipelagic island chain in the eastern Indian Ocean. They are located in Southeast Asia, northwest of Aceh on Sumatra, and separated from Thailand to the east by the Andaman Sea. Located southeast of the Indian s ...

) and on the upper continental slope along the western margin of the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

. The bathymetric range is 380–1000 m.

Reports

W. of Pratas Reef, South of China Sea, 20°37'N, 115°43'E

80 m 8 (eight) is the natural number following 7 and preceding 9. In mathematics 8 is: * a composite number, its proper divisors being , , and . It is twice 4 or four times 2. * a power of two, being 2 (two cubed), and is the first number of t ...

br> E. of Phan Thiet, Vietnam, South China Sea, 10°41'08"N, 109°53'08"E 95–500 mbr> E. of Phan Ly, Vietnam, South China sea, 11°09'06"N, 110°02'00"E 00 mbr> E. of Phan Thiet, Vietnam, South China Sea, 10°01'00"N, 109°55'00"E

60 m 60 metres, or 60-meter dash, is a sprint event in track and field. It is a championship event for indoor championships, normally dominated by the best outdoor 100 metres runners. At outdoor venues it is a rare distance, at least for senior ath ...

br> E. of Ba Ria, Vietnam, South China Sea, 10°40'08"N, 110°03'00"E 60–800 mbr> E. of Phan Ly, Vietnam, South China sea, 11°10'00"N, 110°10'00"E 000–1280 m

References

* Cossignani T. (2006). ''Marginellidae & Cystiscidae of the World''. L'Informatore Piceno. 408pp * Harasewych, M. G. and Y. I. Kantor. 1991. Rediscovery of ... Nemouria 37:1-19. * Lan 1994. World Shells, 8:74-76 * Martens, Eduard C. von and Johannes Thiele 1904. Die beschalten Gastropoden der deutscen Tiefsee-Expedition 1898-1899, 7:147-180,pls. 6-9 * Rehder, Harold A. 1967. Pacific Science, 21(2):182-183; txt-figs. 1-4 * Thiele, Johannes 1929. Handbuch der systematischen ... :356 * Tomlin, John Reed le Brockton 1917. Proc. Malac. Soc., Vol XII, part V-VI:242-306 * Weaver, C.S and J.E. duPont 1970. The Living Volutes :99; plt. 40, figs. H,I * Wenz 1943. Gastropoda: 1380;fig.3903 {{Taxonbar, from=Q6760579, from2=Q21224831 Marginellonidae Gastropods described in 1904