''Bayerotrochus tangaroanus'', or Tangaroan slit shell, is a species of

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

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 ...

in the family

Pleurotomariidae Pleurotomariidae, common name the "slit snails", is a family of large marine gastropods in the superfamily Pleurotomarioidea of the subclass Vetigastropoda. This family is a very ancient lineage; there were numerous species in the geological pas ...

Description

The shell has a typical trochoid shape with a spire angle of approximately 90 degrees and nearly straight sided profile until the later whorls which are slightly rounded with an oblique periphery and a clearly defined suture. The base is inflated and rounded with a small columellar callus at the center covering roughly 10 percent of the base area. The aperture is oval, the slit is positioned roughly halfway between the periphery and the suture and is relatively short, about 16 percent of the circumference. The shell is lightly sculptured with fine spiral threads which are more clearly defined below the

selenizone A selenizone (from the Greek "selene" meaning "moon", and "zone" meaning "girdle") is an anatomical structure that exists in the shells of some families of living sea snails: the slit shells, the little slit shells and the abalones, which are m ...

(the area where the shell growth filled in the slit) crossed by stronger axial growth lines which gives the effect of a weak rectangular pattern. The base has 38 to 40 fine spiral threads. 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 ...

and primary whorls are white and are smooth, the rest of the shell is creamy peach to white, or pale pink, with a slight iridescent sheen and occasional sparse pale reddish axial flammules. Occasionally the selenizone has thin orange lines. The base is the same color as the body, and the interior of the aperture is

nacreous Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is ...

(pearly). The shell is regularly found without a

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

. The operculum is relatively large, roughly circular, pale brown, and multispiral. Its size ranges from 47 to 69 mm in diameter.Anseeuw, P. & Goto, Y., ''The Living Pleurotomariidae'' (1996), Elle Scientific Publications, Osaka Japan, pp. 202, at pp. 148–149.Original description: P. Bouchet & B. Métivier, ''Living Pleurotomariidae (Mollusca: Gastropoda) from the South Pacific'' (1982) Vol. 9:313–316.

Distribution

This species has been found at depths greater than 400 meters from one particular area between the

South Fiji Basin The South Fiji Basin ( also Fiji Basin ) is a large deep oceanic basin in the south-west Pacific Ocean, south of Fiji. It was formed from the then Indo-Australian Plate and is delimited to the north west by the New Hebrides Trench, and the Hunt ...

and Three Kings Rise in the South Pacific north of New Zealand.

References

* Williams S.T., Karube S. & Ozawa T. (2008) ''Molecular systematics of Vetigastropoda: Trochidae, Turbinidae and Trochoidea redefined''. Zoologica Scripta 37: 483–506.

External links

* Pleurotomariidae Gastropods described in 1982 {{Pleurotomariidae-stub