Acila (genus)
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Acila cobboldiae (Pliocene / Pleistocene, Western Europe) |
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| Acila | ||||||||||||
| H. Adams & A. Adams , 1858 |
Acila is a clam genus of the family of nuculidae (Nuculidae) in the order of Nuculida . The oldest representatives of the genus Acila are known from the Barremium (chalk).
features
The same-hinged housing is unequal, the rear housing part is more or less significantly shorter than the front housing part, i. H. the vortex is behind the center. The housings are approximately square, triangular to broadly ovoid in outline, i. H. usually a little longer than high, and more or less bloated. They are only a few millimeters to a few centimeters in size in the adult stage. The rear end can be drawn out into a rostrum, the front end is tightly rounded.
The ligament is sunk, it divides the taxodontic lock into an anterior and posterior part. The front and rear of the lock are at an angle to each other; the angle is less than 90 °. The lock consists of similar, elongated teeth and pits perpendicular to the lock plate, in the front part of the lock there are usually significantly more teeth (up to approx. 30) than in the rear part (approx. 10 to 20). The internal ligament lies in a pit (resilifer).
The ornamentation is different, i. H. consists of front and rear diverging or zigzag ribs and rows of nodules. The edge can be jagged, corresponding to the ribs or rows of knots ending there.
Geographical distribution and habitat
Today's species of the genus Acila occur on the coasts of North and South America and Asia. In the Pliocene and the Lower Pleistocene, they also occurred in the Atlantic.
The animals are buried shallowly in the surface of the sediment and eat detritus. They live almost exclusively in sandy soils. They do not have siphons, but rather cilia create a stream of water that flows in towards the front end and flows out towards the rear end. Thanks to the large foot, they can quickly bury themselves or dig through the sediment.
Taxonomy
The genus was established by the brothers Henry Adams and Arthur Adams in 1858. It is placed in the family or subfamily of nut clams (Nuculidae) or Nuculinae. The genus is divided into two or three sub-genera:
- Genus Acila H. Adams & A. Adams, 1858
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Acila (Acila) H. Adams & A. Adams, 1858, the nominate subgenus (from Eocene to recent)
- † Acila cobboldiae (Sowerby, 1817) (Pliocene / Pleistocene)
- Acila divaricata (Hinds, 1843) (incl.Acila (Acila) divaricata subsp.vengeriana Lautenschläger, 1968)
- † Acila elongata Nagao & Huzioka, 1941 (Neogen)
- † Acila ermanni Girard, 1843 (?)
- Acila fultoni (EA Smith, 1892)
- † Acila gettysburgensis (Reagan, 1909)
- Acila granulata (EA Smith, 1906)
- Acila jucunda (Thiele & Jaeckel, 1931)
- † Acila kholmskensis Krishtofovich, 1964
- Acila minutoides Kuroda & Habe in Habe, 1958
- Acila mirabilis (Adams & Reeve, 1850)
- † Acila paita Olsson, 1931 ( Chattium )
- † Acila plura Olsson, 1931 ( Oligocene )
- † Acila praedivaricata Nagao & Huzioka, 1941
- † Acila semirostrata Grant & Gale, 1931 (Miocene)
- † Acila stillwaterensis Weaver & Palmer, 1922 ( Eocene )
- Acila vigilia Schenck, 1936
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Acila (Truncacila) Schenck in Grant & Gale, 1931. The subgenus is characterized by the almost complete absence of a rostrum and by its small size.
- † Acila allisoni Squires & Saul, 2004 (Upper Aptium )
- † Acila beringiana Slodkewitsch, 1967
- † Acila blancoensis Howe, 1922 ( Miocene )
- Acila castrensis (Hinds, 1843) (Pliocene to recent)
- † Acila conradi (Meek, 1864)
- † Acila decisa (Conrad, 1855) (incl.Acila (Truncacila) decisa (Conrad) ilpinensis Pronina, 1980)
- † Acila demessa Finlay, 1927
- † Acila eximia (Yokoyama, 1925)
- † Acila galinae Slodkewitsch, 1967 (Nevel'skaya Suite: Lower / Middle Miocene)
- † Acila gottschei (Böhm, 1916)
- † Acila grahami Squires & Saul, 2004
- † Acila haidana Packard in Schenck, 1936
- † Acila himenourensis Tashiro, 1985 ( Cenomanium )
- † Acila hokkaidoensis (Nagao, 1932) ( Campanium )
- Acila insignis (Gould, 1861) (Miocene / Pliocene)
- † Acila longa Kalishevich, 1969
- † Acila marujamensis Ilyina, 1957 ( Maruyamskaya Suite : Upper Miocene / Lower Pliocene)
- Acila markovskensis Devjatilova, 1981
- † Acila munda Kalishevich, 1969
- † Acila oyamadensis Hirayama, 1955
- † Acila parva Devjatilova, 1981
- † Acila packardi (Clark)
- † Acila pecticostata Kalishevich, 1969
- † Acila pleschakovi Krishtofovich, 1947
- † Acila praevigilia Krishtofovich in Gladenkov et al., 1984
- † Acila princeps Schenck, 1943
- † Acila rosaria Squires & Saul, 2004
- Acila shumardi (Dall, 1909)
- † Acila triangula Kalishevich in Kalishevich et al., 1981
- † Acila vereshagini Kalishevich, 1969
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Acila (Acila) H. Adams & A. Adams, 1858, the nominate subgenus (from Eocene to recent)
The subgenus Acila (Lacia) Slodkewitsch, 1967 (type species: Nucula (Acila) shumardi Dall, 1909) is not recognized by the checklist and is included in the synonymy of Acila (Truncacila) . According to Ellen Moore, the genus was also not validly established because no diagnostic features were given that distinguish the taxon from Acila (Acila) and Acila (Truncacila) .
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. 12)
- Raymond C. Moore : Treatise on Invertebrate Paleontology. Part N: Mollusca. 6, Bivalvia. Vol. 2. The University of Kansas et al., Boulder CO 1969 (S.N231)
- 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 (p.)
- Hubert G. Schenck: Nuculid Bivalves of the Genus Acila. Geological Society of America Special Papers, 4: 1936 Limited preview on Google Books
- Richard Squires, Louella R. Saul: Cretaceous Acila (Truncacila) (Bivalvia: Nuculidae) from the Pacific Slope of North America. The Veliger, 48 (2): 83-104, 2006 []
Individual evidence
- ^ Henry Adams & Arthur Adams: The genera of recent Mollusca; arranged according to their organization. In three volumes. Vol. II. Pp. 1–661, London, Van Voorst, 1858. Online at www.biodiversitylibrary.org (p. 545)
- ^ A b World Register of Marine Species: Acila H. Adams & A. Adams, 1858
- ↑ a b c d e f g h i j k l m n o p q r s t u v Alexander I. Kafanov, Kenshiro Ogasawara, Louie Marincovich: Checklist and bibliography of the Cenozoic marine Bivalvia (Mollusca) of Northeastern Asia (Russian Far East), 1968-1999. Bulletin of the Mizunami Fossil Museum, 28: 1-138, 2001 PDF
- ↑ a b Steffen Kiel, Kazutaka Amano, Robert G. Jenkins: Bivalves from Cretaceous cold − seep deposits on Hokkaido, Japan. Acta Palaeontologica Polonica. 53 (3): 525-537, 2008 PDF
- ↑ Ellen James Moore: Oligocene marine mollusks from the Pittsburg Bluff Formation in Oregon. Geological Survey Professional Paper, 922: Washington 1976 Online at Google Books ()
