Atlantidae
Encyclopedia
Atlantidae is a family
of sea snail
s, holoplankton
ic gastropod molluscs in the clade
Littorinimorpha
.
According to taxonomy of the Gastropoda by Bouchet & Rocroi (2005)
the family Atlantidae has no subfamilies.
to pelagic life, in the form of a lenticular, laterally flattened, aragonitic shell, the surface of which is further enlarged by the presence of a wide, and very thin and fragile, double-walled keel. The apex is on the right side of the shell, the umbilicus on the left. For the living animal the enlargement of the shell’s surface serves ‘to increase stabilization during swimming and sinking’. This phenomenon results in the occurrence of superficially very similar adult shells in separate species, whereas the larval shells may be utterly different.
Their body size is microscopic with a shell diameter of less than 1 cm. The foot has evolved into a muscular swimming fin. Their swimming fin extends anteriorly beneath their head. They swim with their ventral part upward through undulation of their swimming fin.
The shell is coiled dextrally (i.e. clockwise). The thin, double-walled keel of the shell extends outward from the last shell whorl. The apex
of the shell is found on the right side, the umbilicus on the left side. The shell and keel can be calcareous (genus Atlanta), or composed exclusively of conchiolin
(genus Oxygyrus), or the shell can be calcareous and its keel composed of conchiolin (genus Protatlanta). The snails of this family can retract into their shell and close it off with a cartilaginous, flexible operculum
.
Recent Atlantidae, in the present concept, comprise three genera, two of which, Oxygyrus Benson, 1835, and Protatlanta Tesch, 1908, are considered monospecific. In Protatlanta, however, a few additional fossil species have been described. Both genera are characterised by partially uncalcified (conchiolin
) shell portions. Additional fossil genera considered to belong in the Atlantidae are Bellerophina d’Orbigny, 1843 (Cretaceous
), Eoatlanta Cossmann, 1888 (Paleocene-Eocene) and Mioatlanta di Geronimo, 1974 (Miocene). Only few Atlanta species are known from the fossil record, the oldest one being Atlanta arenularia Gougerot & Braillon, 1965 is from the Bartonian
of the Paris Basin, which differs considerably from typical Atlanta by its cornucopia shape.
to which they attach themselves. They are active predator locating their prey visually.
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...
of sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
s, holoplankton
Holoplankton
Holoplankton are organisms that are planktonic for their entire life cycle. Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps.-Sources:Asexual Holoplankton:...
ic gastropod molluscs in the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Littorinimorpha
Littorinimorpha
Littorinimorpha is a large clade of gastropods within Hypsogastropoda consisting primarily of marine species, but also aquatic and terrestrial species as well....
.
According to taxonomy of the Gastropoda by Bouchet & Rocroi (2005)
Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
the family Atlantidae has no subfamilies.
Description
The Atlantidae is a group of holoplanktonic gastropods, which all demonstrate a strong adaptationAdaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
to pelagic life, in the form of a lenticular, laterally flattened, aragonitic shell, the surface of which is further enlarged by the presence of a wide, and very thin and fragile, double-walled keel. The apex is on the right side of the shell, the umbilicus on the left. For the living animal the enlargement of the shell’s surface serves ‘to increase stabilization during swimming and sinking’. This phenomenon results in the occurrence of superficially very similar adult shells in separate species, whereas the larval shells may be utterly different.
Their body size is microscopic with a shell diameter of less than 1 cm. The foot has evolved into a muscular swimming fin. Their swimming fin extends anteriorly beneath their head. They swim with their ventral part upward through undulation of their swimming fin.
The shell is coiled dextrally (i.e. clockwise). The thin, double-walled keel of the shell extends outward from the last shell whorl. The apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
of the shell is found on the right side, the umbilicus on the left side. The shell and keel can be calcareous (genus Atlanta), or composed exclusively of conchiolin
Conchiolin
Conchiolin and perlucin are complex proteins which are secreted by a mollusc's outer epithelium ....
(genus Oxygyrus), or the shell can be calcareous and its keel composed of conchiolin (genus Protatlanta). The snails of this family can retract into their shell and close it off with a cartilaginous, flexible 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...
.
Genera
Genera in the family Atlantidae include:- Atlanta Lesueur, 1817 - type genus
- Oxygyrus Benson, 1835 - monospecific, it has only one species Oxygyrus keraudreniiOxygyrus keraudreniiOxygyrus keraudrenii is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.Oxygyrus keraudrenii is the only species in the genus Oxygyrus.-Description:...
(Lesueur, 1817) - ProtatlantaProtatlantaAtlanta is a genus of pelagic marine gastropod molluscs in the family Atlantidae.-Species:Species in the genus Atlanta include:* Protatlanta souleyeti - type species and the only Recent species in the genus Protatlanta...
Tesch, 1908 - monospecific in extant species; a few fossil species have been described - † Bellerophina d’Orbigny, 1843
- † Eoatlanta Cossmann, 1888
- † Mioatlanta di Geronimo, 1974
Recent Atlantidae, in the present concept, comprise three genera, two of which, Oxygyrus Benson, 1835, and Protatlanta Tesch, 1908, are considered monospecific. In Protatlanta, however, a few additional fossil species have been described. Both genera are characterised by partially uncalcified (conchiolin
Conchiolin
Conchiolin and perlucin are complex proteins which are secreted by a mollusc's outer epithelium ....
) shell portions. Additional fossil genera considered to belong in the Atlantidae are Bellerophina d’Orbigny, 1843 (Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
), Eoatlanta Cossmann, 1888 (Paleocene-Eocene) and Mioatlanta di Geronimo, 1974 (Miocene). Only few Atlanta species are known from the fossil record, the oldest one being Atlanta arenularia Gougerot & Braillon, 1965 is from the Bartonian
Bartonian
The Bartonian is, in the ICS's geological timescale, a stage or age in the middle Eocene epoch or series. The Bartonian age spans the time between and . It is preceded by the Lutetian and is followed by the Priabonian age.-Stratigraphic definition:...
of the Paris Basin, which differs considerably from typical Atlanta by its cornucopia shape.
Ecology
Atlantids are negatively buoyant. During the day, they have to swim to maintain their position. At night they secrete strands of buoyant mucusMucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
to which they attach themselves. They are active predator locating their prey visually.