Bayerotrochus tangaroanus
Encyclopedia
Bayerotrochus tangaroanus, common name : the Tangaroan Slit Shell, is a species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....

, a marine gastropod mollusk in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Pleurotomariidae
Pleurotomariidae
Pleurotomariidae, common name the '"slit snails", is a family of large marine gastropods in the clade Vetigastropoda. This family is very ancient; there were numerous species in the geological past. It is currently represented by a group of species that live only in deep water...

.

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
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....

 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 (the area where the shell growth filled in the slit) crossed by stronger axial growth lines which gives the affect of a weak rectangular pattern. The base has 38 to 40 fine spiral threads. The protoconch
Protoconch
A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...

 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 (pearly). The shell is regularly found without a periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...

. The operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...

 is relatively large, roughly circular, pale brown, and multispiral. Size range: 47 to 69 mm diameter.

Distribution

This species has been found at depths greater than 400 meters from one particular area between the South Fiji Basin and Three Kings Rise in the South Pacific north of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

.

External links

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