Lyonsiidae

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Lyonsiidae
Norwegian beak mussel (Lyonsia norwegica) (from GB Sowerby II, 1859: Plate 2, Fig. 4 [1])

Norwegian beak mussel ( Lyonsia norwegica ) (from GB Sowerby II, 1859: Plate 2, Fig. 4)

Systematics
Subclass : Heterodonta
Euheterodonta
Superordinate : Anomalodesmata
Order :
Superfamily : Pandoroidea
Family : Lyonsiidae
Scientific name
Lyonsiidae
P. Fischer , 1887

The Lyonsiidae are a biology of the mussels from the large group of the Anomalodesmata . It is a comparatively small family with almost 50 recent species and an as yet undetermined number of fossil species. The oldest members of the family date from the Paleocene . The Lyonsiidae are sometimes also called beaked clams, but should not be confused with the clam family Cuspidariidae , which are also called beaked clams .

features

The unevenly hinged housings are very small (2 mm) to medium-sized (over 10 cm). The left flap is generally slightly larger than the right flap and protrudes more or less clearly. The housings are rounded-square, rounded to elongated-egg-shaped. They are unequal, the vertebrae , curled forward, lie in front of the center. In many species, the housing gapes at the rear end. The ligament lies internally on both sides of a calcareous plate (Lithodesma). In many species the thick periostracum is fused dorsally and forms a kind of secondary ligament. Lock teeth are missing. The surface line is deeply indented. There are two comparatively small sphincters. Usually they are about the same size, but in some species the anterior sphincter is significantly larger.

The aragonitic shell is thin and fragile. It consists of an inner layer of layered mother-of-pearl , a middle layer of lenticular mother-of-pearl and an outer prismatic layer. The latter is relatively thin in relation to the thickness of the two mother-of-pearl layers. In some species the middle layer is granular-prismatic. The periostracum is thin to very thick, sediment particles often adhere or it has embedded needle-like lime crystals. The periostracum can also flake off easily. The ornamentation consists of more or less strong growth strips parallel to the edge. Radial elements can also be present.

The siphons are short and not grown together. The foot is large and narrowed at the side, or small with a byssus pit. The byssus persists into the adult stage.

Geographical distribution and habitat

The family is distributed worldwide in shallow waters (mostly only a few tens of meters deep). They live buried flat in the sediment or as nestlers on the sediment surface. Some species also live in association with sponges (Porifera) or sea ​​squirts (Ascidiae).

Taxonomy

The family was proposed by Paul Fischer in 1887. It is widely accepted today.

supporting documents

literature

  • Eugene V. Coan, Paul Valentich-Scott: Bivalve Seashells of Tropical West America marine Bivalve mollusks from Baja california to Northern Perú. Part 2. Santa Barbara Museum of Natural History, Santa Barbara 2012 ISBN 978-0-936494-43-2 (p. 971)
  • S. Peter Dance, Rudo von Cosel (arrangement of the German edition): The great book of sea shells. 304 p., Verlag Eugen Ulmer, Stuttgart, 1977 ISBN 3-8001-7000-0 (p. 273)
  • Myra Keen: Family Lyonsiidae Fischer, 1887. In: Raymond Cecil Moore (Ed.): Treatise on invertebrate paleontology. Mollusca, 6, Bivalvia 2. S.N845 / -N847, New York, 1969.
  • 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. 156)
  • Guido Poppe. Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 pp., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3925919104 (p. 136)
  • Fengshan Xu: On the family Lyonsiidae (Mollusca: Bivalvia), with description of a new genus and species from the China seas. Chinese Journal of Oceanology and Limnology, 10 (2): 153-155, 1992 doi : 10.1007 / BF02844746

Individual evidence

  1. ↑ George Brettingham Sowerby II : Illustrated index of British shells. containing figures of all the recent species, with names and other information. XV S., XXIV Plate London, Simpkin, Marshall & Co., 1859 Online at www.biodiversitylibrary.org (Plate 2, Fig. 4)
  2. ↑ Fritz Gosselck, Alexander Darr, Jürgen HJ Jungbluth, Michael Zettler: Trivial names for mollusks of the sea and brackish water in Germany. Mollusca, 27 (1): 3-32, 2009 PDF
  3. ^ Paul Fischer (in collaboration with SP Woodward and DP Oehlert): Manuel de conchyliologie et de paleontologie conchyliologique: ou histoire naturelle des mollusques vivants et fossiles. XXIV, 1369 S., Savy, Paris 1880 - 1887 Online at www.biodiversitylibrary.org (p. 1162)
  4. ↑ MolluscaBase: Lyonsiidae P. Fischer, 1887