''Halystina umberlee'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of very small deep-water

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Seguenziidae Seguenziidae is a family (biology), family of very small deepwater sea snails, marine (ocean), marine gastropod mollusks in the superfamily Seguenzioidea (according to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastr ...

Taxonomy

''Halystina umberlee'' belongs in the genus '' Halystina'', a group of small-sized sea snails with a rounded shell profile, flat-sided whorls and finely granulate

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 " ...

. It is considered to resemble species in the genus '' Halystes'', differing only by its much smaller size. It was named after Umberlee, a fictional goddess from the Faerûnian pantheon of the

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campaign setting for the

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fantasy

role-playing game A role-playing game (sometimes spelled roleplaying game, or abbreviated as RPG) is a game in which players assume the roles of player character, characters in a fictional Setting (narrative), setting. Players take responsibility for acting out ...

Description

''Halystina umberlee'' is a very small species, barely reaching a shell height of 2 mm. It has a rounded, conic to turbinate shell, with relatively thick walls and up to 5

whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagram ...

. Its bulbous

consists of a single whorl with a pitted surface, and the protoconch-teleoconch transition is marked by a thin line. The

teleoconch The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium ...

has 4 convex whorls,

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by delicate spiral cordlets crossed by axial threads, forming a delicate net-like pattern. The axial threads form an overall continuous

sigmoid Sigmoid means resembling the lower-case Greek letter sigma (uppercase Σ, lowercase σ, lowercase in word-final position ς) or the Latin letter S. Specific uses include: * Sigmoid function, a mathematical function * Sigmoid colon, part of the l ...

pattern along the shell's longitudinal axis, and the spiral sculpture becomes gradually weaker toward the basal region of

last whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

. The basal part of the shell is sculptured by 10-12 spiral cords, but the umbilical region is smooth, with a well-marked margin. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

is quadrangular, and bears three deep sinuses. The shell is colored glossy white, with a

nacre 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 ...

ous shade.

Distribution

This marine species occurs off southeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, from

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, at 950–1550 m depths.

References

{{Taxonbar, from=Q19636614 Halystina Gastropods described in 2014