Bathyarca

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Bathyarca
Bathyarca pectunculoides (from Kobelt, 1891: Pl. 5, Fig. 6, 7)

Bathyarca pectunculoides (from Kobelt, 1891: Pl. 5, Fig. 6, 7)

Systematics
Subclass : Pteriomorphia
Order : Arcida
Superfamily : Arcoidea
Family : Ark clams (Arcidae)
Subfamily : Bathyarcinae
Genre : Bathyarca
Scientific name
Bathyarca
Kobelt , 1891

Bathyarca is a shell - genus from the family of ark shells (Arcidae). Bathyarca is the type genus of the subfamily Bathyarcinae. The oldest species of the genus Bathyarca comes from the Eocene of New Zealand .

features

The housings are slightly unevenly hinged. the left flap is slightly larger than the right flap, which is practically in the left flap. They are rounded in outline, wedge-shaped to oblong-ovoid, the greatest height is in the rear part of the housing. They are usually very small to small. The length of the adult housing ranges from about four millimeters to (very rarely) 15 millimeters (up to 28 millimeters: Bathyarca glacialis ). The casing is only slightly longer than high, rarely also a little longer than high ( Bathyarca glacialis ). They are not bloated, i.e. not particularly thick (both valves considered). The rear part of the housing is more or less extended. The lower vertebra sits in front of the middle in relation to the total dorsal length, about a third to a quarter from the anterior margin. The dorsal margin is more or less long and straight in relation to the total length. At the posterior end, the dorsal margin is broadly rounded or angled into the moderately to strongly curved posterior margin. The anterior dorsal margin is tightly rounded to angled and merges into the anterior margin. The rear and front edges merge into the ventral edge without any noticeable change in curvature. The indentation for the byssus is not very pronounced. The inner edge of the housing of the left flap has a weak serration, the inner edge of the right flap is smooth.

The lock is taxodont , the lock plate is usually narrow and slightly curved. The weak teeth in the anterior part are crooked, the teeth in the rear are usually more oblique than the anterior teeth, almost parallel to the dorsal margin. The ligament is always very narrow, often rhombic, egg-shaped or deltoid (dragon square).

The whitish translucent shell is thin and fragile. The fine and weak ornamentation consists of fine radial and dense lines, which are usually somewhat stronger than the fine concentric growth strips. The inner edge of the case is slightly serrated on the larger, left flap, but smooth on the smaller, right flap.

The muscle attachment points can only be seen indistinctly. Of the two sphincters, the anterior sphincter is slightly smaller than the posterior sphincter. The surface line is entire without indentation.

Similar genera

In Bentharca , the rear lock teeth are usually arranged approximately parallel to the lock edge. The cases are usually much longer than they are high. The radial ribs are much stronger.

Geographical distribution and habitat

The species of the genus occur worldwide in deeper water (from approx. 200 meters water depth) to over 5000 meters water depth. Some species occasionally also rise in somewhat shallower water (up to approx. 50 meters water depth).

Taxonomy

The taxon was first described in 1891 by Wilhelm Kobelt . Type species is Arca pectunculoides Sacchi, 1835. The World Register of Marine Species assigns a little over 30 species to the genus. There is no newer revision of the genre.

The World Register of Marine Species lists two synonyms for the genus Bathyarca , Microcucullaea Iredale, 1929 and Thronacar Iredale, 1939. Markus Huber (2010) considers Microcucullaea Iredale, 1929 to be distinguishable, at least at the subgenus level.

supporting documents

literature

  • Rudolf Kilias: Lexicon marine mussels and snails. 2nd edition, 340 p., Verlag Eugen Ulmer, Stuttgart 1997 ISBN 3-8001-7332-8 (p. 45)
  • Raymond Cecil Moore (Ed.): Treatise on invertebrate paleontology. Mollusca, 6, Bivalvia 1. XXXVIII, 489 pp., New York, 1969 (pp. N254).
  • Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. 256 p., Gustav Fischer Verlag, Stuttgart 1969 (in the following abbreviated, Nordsieck, sea shells with corresponding page number)

Individual evidence

  1. ↑ Marine Bivalve Shells of the British Isles: Bathyarca glacialis (JE Gray, 1824) (website of the National Museum Wales, Department of Natural Sciences, Cardiff)
  2. ↑ Nordsieck, sea shells, p. 22.
  3. ^ Wilhelm Kobelt: The genus Arca L. In illustrations after nature with descriptions. Systematic Conchylia Cabinet by Martini and Chemnitz. 8th volume, 2nd department, 238 p., Bauer & Raspe, Nuremberg, 1891 Online at www.biodiversitylibrary.org (p. 214)
  4. ^ A b World Register of Marine Species: Bathyarca Kobelt, 1891
  5. ^ Markus Huber: Compendium of bivalves. 901 S., Hackenheim, ConchBooks, 2010 ISBN 978-3-939767-28-2

annotation

  1. ↑ Due to the strong ribbing, this species does not belong to Bathyarca , but to Asperarca .