Marginellona gigas

Marginellona gigas
Two views of a shell of Marginellona gigas trawled in 600m Pratas Islands, Taiwan
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
(unranked):	clade Caenogastropoda clade Hypsogastropoda clade Neogastropoda
Superfamily:	Muricoidea
Family:	Marginellidae
Subfamily:	Marginelloninae
Genus:	Marginellona
Species:	M. gigas
Binomial name
Marginellona gigas Martens, 1904
Synonyms
Sigaluta pratasensis Rehder, 1967

Marginellona gigas is a species of very large deepwater sea snail, a marine gastropod mollusk in the family Marginellidae. This species was originally thought to be a volute, in the family Volutidae, but it is in fact a giant marginellid.

This is the only known species in the genus Marginellona, in other words, Marginellona is a monotypic genus.

Shell description

The shell can be as large 157 mm. It is thin, translucent, porcellaneous, and narrowly ovate in shape. The protoconch 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 15º. 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 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 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, 07º48'N, 92º07'E, in 805 m, coarse sand.

Distribution

This species has been collected in the eastern Indian Ocean (Nicobar Islands) and on the upper continental slope along the western margin of the South China Sea. The bathymetric range is 380-1000 m.

Reports

W. of Pratas Reef, South of China Sea, 20º37'N, 115º43'E [380 m]
E. of Phan Thiet, Vietnam, South China Sea, 10º41'08"N, 109º53'08"E [495-500 m]
E. of Phan Ly, Vietnam, South China sea, 11º09'06"N, 110º02'00"E [700 m]
E. of Phan Thiet, Vietnam, South China Sea, 10º01'00"N, 109º55'00"E [460 m]
E. of Ba Ria, Vietnam, South China Sea, 10º40'08"N, 110º03'00"E [760-800 m]
E. of Phan Ly, Vietnam, South China sea, 11º10'00"N, 110º10'00"E [1000-1280 m]

References

• 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