''Oxygyrus keraudrenii'' 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 ...

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

holoplankton Holoplankton are organisms that are plankton, planktic (they live in the water column and cannot swim against a current) for their entire life cycle. Holoplankton can be contrasted with meroplankton, which are planktic organisms that spend part of ...

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 ...

Atlantidae Atlantidae is a family of sea snails, holoplanktonic gastropod molluscs in the clade Littorinimorpha. According to taxonomy of the Gastropoda by Bouchet & Rocroi (2005) the family Atlantidae has no subfamilies. Description The Atlantidae is a ...

. ''Oxygyrus keraudrenii'' is the only species in the genus ''Oxygyrus''.

Description

''Oxygyrus keraudreni'' (along with '' Atlanta peronii'') attains the largest size (shell diameter to 10 mm) among the Atlantidae.Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLoS ONE'' 5(1): e8776. . Body coloration is light bluish-purple, with the color darkening with age. The larval shell is

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

and displays a distinctive pattern of zigzag-shaped spiral ridges that are evenly spaced and cover the shell surface. The teleoconch is composed of

conchiolin Conchiolins (sometimes referred to as conchins) are complex proteins which are secreted by a mollusc's outer epithelium (the mantle). These proteins are part of a matrix of organic macromolecules, mainly proteins and polysaccharides, that assem ...

, a transparent cartilaginous material, and its surface lacks

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

. With growth the teleoconch overgrows 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 eventually surrounds it. A shell

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

, as seen in all other atlantids, is lacking and the spire region is termed involute. The conchiolin keel is glass-like and has a truncate anterior edge that ends at the shell

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 ...

. The shell of this easily recognisable species is completely involute, with a similar ‘umbilicus‘ at both the top and the base of the shell. This feature makes it impossible to count the number of protoconch whorls, as only one is visible in each of them. The juvenile shell initially is slightly wider than high, but gets relatively wider during growth. Its surface is slightly irregularly covered with approximately 20-24 spiral lirae in a zigzag-shape that usually leave a narrow zone free just below the periphery. In between these lirae the shell’s surface is granulated. The apertural margin of the shell is deeply sinuated, as can be seen from the shape of the growth lines and also at the place where the ornamented protoconch changes quite suddenly to the much less clearly ornamented teleoconch (this transition is well-illustrated by Thiriot-Quiévreux, 1973, fig. 1A, and Batten & Dumont, 1976, fig. 24). In the largest available specimen from Pliocene of Philippines, the teleoconch has one complete whorl, widening rapidly, which makes the shell about twice as wide as high. In this specimen the apertural margin is irregularly broken, indicating that the teleoconch might even have more than one calcified teleoconch whorl in complete specimens. In another specimen from Philippines (H = 1.60, W = 2.52 mm), the teleoconch has three quarters of a whorl. On the post-larval shell a vague spiral ornament is present and the peripheral belt remains visible as a slightly produced zone reaching the apertural margin. The type c eye morphology is only seen in one other species of atlantid ('' Atlanta helicinoides'') and one carinariid ('' Cardiapoda richardi''). The shape of the operculum is unique among atlantids, broadly triangular, approaching trapezoidal in shape, and lacking the apical spiral part present in all other atlantids. Also unique to the operculum is that when the animal retracts into its shell, only about one-half of the operculum covers the shell aperture. The

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

is very large and is triangular in shape. Recent specimens of ''Oxygyrus keraudreni'' have an uncalcified

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

in the adult stage. Janssen (2007) have found an indication that, during the Pliocene, individuals of this species were yet further calcified than are extant specimens. This could point to a developmental trend involving a reduction of calcareous matter in the course of time, as a gradual weight reduction beneficial for

ic life. The distinct peripheral belt demonstrates that a conchiolin keel was present.

Distribution

The geographical distribution is

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

in tropical to subtropical waters.

Fossil distribution

From the fossil record ''Oxygyrus keraudrenii'' has been found from

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Tiep ''Tiep'' or ''thieb'' is a traditional dish from Senegal that is also consumed in Guinea-Bissau, Guinea, Mali, Mauritania, and The Gambia. It is the national dish in Senegal. The version of tiep called ''thieboudienne'' or ''chebu jen'' ( wo, ...

, Roxas
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and

Anda, Pangasinan Anda, officially the Municipality of Anda ( pag, Baley na Anda; ilo, Ili ti Anda; tgl, Bayan ng Anda), is a 3rd class municipality in the province of Pangasinan, Philippines. According to the 2020 census, it has a population of 41,548 people. ...

, Luzon, Philippines in 2001 (published in 2007). ''Oxygyrus keraudrenii'' is known, in very few specimens only, from Jamaica (Janssen, 1998) and the Mediterranean Pliocene (Italy, Spain, France; Janssen, 2004). The French occurrence was dated as

Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and fol ...

and thus it may be assumed that ''Oxygyrus'' occurred approximately since the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 Miocene representatives or related forms are unknown.

Habitat

''Oxygyrus keraudreni'' is a shallow-dwelling species that normally occurs in low abundances. In the Indian Ocean was ''Oxygyrus keraudreni'' found essentially limited to the upper 100 m of the water column, with 90% between 50 m and the surface. Similarly, off Hawaii was it recorded low in numbers of individuals whose vertical range was limited to the upper 90 m of the water column, with most individuals occurring at night in the upper 45 m. In another study from the same area off Hawaii it was found that ''Oxygyrus keraudreni'' was captured in nighttime tows but was either absent or nearly so from comparable daytime ones. The results from the latter two studies suggest the possibility of daytime net avoidance.

References

This article incorporates CC-BY-3.0 text from references.Seapy R. R. (2010). ''Oxygyrus keraudreni'' Benson 1835. Version 1 April 2010. http://tolweb.org/Oxygyrus_keraudreni/28753/2010.04.01 in The

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site h ...

, accessed 20 August 2010. {{Taxonbar, from1=Q18580270, from2=Q3139351 Atlantidae Extant Pliocene first appearances Gastropods described in 1835 Taxa named by William Henry Benson