| Atlanta | |
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| Atlanta anatomy | |
| Scientific classification | |
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| Genus: | Atlanta Lesueur, 1817 |
| Type species | |
| Atlanta peronii Lesueur, 1817 | |
| Species | |
See text | |
| Synonyms [2] | |
SteiraEschscholtz, 1825 | |
Atlanta is a genus of pelagic marine gastropod molluscs in the family Atlantidae. They are sometimes called heteropods. [2]
All of the nineteen species but one, Atlanta californiensis , dwell in tropical and subtropical waters. [3] The majority of species (ten) are cosmopolitan and, among the remaining nine species, five are Indo-Pacific, two are restricted to the Pacific Ocean, one is Indo-Atlantic, and one is limited to the Atlantic Ocean. [3]
They are floating or swimming snails in tropical and subtropical seas. Most have a cosmopolitan distribution, but A. brunnea, A. pulchella and A. quoyi are only found in American waters. A. fusca, A. pacifica and A. rosea are restricted the seas around Japan.
It has been recognized by several authors that identification of species in this genus is difficult and is dependent on their morphology of eyes, radula and operculum.
Main diagnostic features include: the shell and keel are calcareous; [3] larval shell becomes the spire in the adult shell. [3]
Snails of this genus are very small. Their coiled, calcareous [3] shell has a diameter of less than 1 cm. The protoconch of the larval shell is retained after metamorphosis and becomes the spire of the adult shell. [3] The number of spire whirls varies from 2½ (in the A. lesueuri- group) to 6 (A. gibbosa) and is thus also helpful in the identification of a species. The spire shape differs between the species groups, from very small (A. lesueuri- group), to inflated or flat (A. inflata- group ) to large (A.inclinata- group and A. gibbosa- group).
They can retract into their shell and close it off with an operculum. This operculum is cartilaginous and flexible. In 1961 Richter distinguished three types of the operculum [4] in which the larval gyre of the operculum is apical. This gyre can be relatively somewhat larger (macro-oligogyre), smaller (micro-oligogyre) or a single gyre (monogyre).
The eye morphology also consists of three types with differences in pigmented region between the lens and the retina.
The radula is typically taenioglossate with one central (rachidian) tooth, with on each side one lateral tooth and two marginal teeth. In 13 species the number of tooth rows increases during growth (Type I), while in 8 species the radula has a limited number of tooth rows (Type II). [4]
Many authors (e.g., Thiriot-Quiévreux, 1973, p. 240; Richter, 1974, p. 60; Seapy, 1990, p. 107) admit that identification of Atlanta species is difficult and including soft-part features (eyes, radula, operculum) or application of transmitted light to observe inner shell structures (Richter, 1987, p. 178) are very helpful in distinguishing species with similar shells. [1] However, such methods are unavailable for fossil material. [1] This makes identifying fossil species of Atlanta quite difficult and even well-preserved specimens occasionally can only be related to existing taxa with a query (e.g., Atlanta sp. in Janssen, 2004, p. 108; Atlanta cf. echinogyra in Jansen 2007). [1] Advantageous in this study of fossil atlantids, however, is the fact that all specimens are preserved as opaque aragonitic shells as a result of recrystallisation, which facilitates assessing protoconch shape and ornament with a normal 25 or 50× binocular magnification, they are thus much easier studied than in the usually very transparent and shiny Recent specimens. [1] Still, here, too, study of the larval shell shape and micro-ornamentation by SEM is highly desirable or even indispensable. [1]
Atlanta includes a large number of Recent species. Lalli & Gilmer (1989) [5] listed 14 species, but Richter & Seapy (1999) [6] recognised 21 extant species, provisionally subdivided into seven 'species groups' (and one species unassigned). [1] A further Recent species was described since; Atlanta selvagensis de Vera & Seapy, 2006. [1]
Species in the genus Atlanta include:
Based on similar morphologies, these species have been placed in seven species groups: [3] [29]
| Atlanta (19 recent species) |
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Tesch (1908) was the first to group together the species of Atlanta sharing similar morphologies. [3] He recognized four species groups; the Atlanta peronii-, Atlanta inflata-, Atlanta turriculata-, and Atlanta inclinata-groups. [3] In addition to these four, three additional ones are currently recognized; the Atlanta lesueurii-, Atlanta gaudichaudi- and Atlanta gibbosa groups. [3] Except for Tesch's Atlanta turriculata-group, the composition of Tesch's species groups has changed by species invalidations, the addition of new species over time, and addition of three new species groups. [3] The main changes in Tesch's species groups have occurred in the Atlanta peronii-group (with Atlanta gaudichaudi and Atlanta lesueurii now forming their own species groups) and the Atlanta inclinata-group (the Atlanta gibbosa now forming its own group). [3]
Dolabrifera is a genus of sea hares, a taxonomic group of sea slugs or marine opisthobranch gastropod mollusks belonging to the family Aplysiidae.
Limacina is a genus of swimming predatory sea snails commonly known as sea butterflies in the family Limacinidae. This genus contains some of the world's most abundant gastropod species.
The Clionidae are a family of sea angels, which are a group of pelagic marine gastropods.
Tegula is a genus of small to medium-sized sea snails, marine gastropod molluscs in the family Tegulidae.
The Trochidae, common name top-snails or top-shells, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda.
The Vermetidae, the worm snails or worm shells, are a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha. The shells of species in the family Vermetidae are extremely irregular, and do not resemble the average snail shell, hence the common name "worm shells" or "worm snails".
Hipponicidae, common name hoof shells or hoof snails, is a family of small sea snails, limpet-like marine gastropod molluscs in the superfamily Vanikoroidea.
Amathinidae, is a taxonomic family mostly consisting of small and minute sea snails, marine heterobranch gastropod molluscs or micromolluscs in the superfamily Pyramidelloidea.
Lottiidae is a family of sea snails, specifically true limpets, marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda.
Liotiidae is a family of small sea snails, marine gastropod mollusks in the clade Vetigastropoda.
Crepidula, commonly known as the slipper snails, slipper limpets, or slipper shells, is a genus of sea snails, marine gastropod mollusks in the family Calyptraeidae. This family includes the slipper snails (Crepidula), hat snails (Calyptraea), spiny slipper snails (Bostrycapulus), and cup-and-saucer snails (Crucibulum) as well as Crepipatella, Siphopatella, Grandicrepidula, and Maoricrypta.
Bittium is a genus of very small sea snails, marine gastropod molluscs in the family Cerithiidae, the horn snails.
Heleobia is a genus of small freshwater and brackish water snails with a gill and an operculum, aquatic gastropod mollusks in the family Cochliopidae and the superfamily Truncatelloidea.
Patella is a genus of sea snails with gills, typical true limpets, marine gastropod mollusks in the family Patellidae, the true limpets.
Cerithidea is a genus of medium-sized sea snails or mud snails, marine gastropod mollusks in the family Potamididae, the horn snails.
Pyramidella is a genus of minute to medium-sized sea snails, marine gastropod mollusk in the family Pyramidellidae, the pyrams and their allies.
Phidiana is a genus of sea slugs, aeolid nudibranchs, marine gastropod molluscs in the family Facelinidae.
Atlanta californiensis is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.
Atlanta inclinata is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae.
Crenella is a genus of bean mussels in the family Mytilidae.
This article incorporates CC BY-3.0 text from references. [1] [3]
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