Hammer clams

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Hammer clams
White hammer clam (Malleus albus)

White hammer clam ( Malleus albus )

Systematics
Sub-stem : Shell molluscs (Conchifera)
Class : Mussels (Bivalvia)
Subclass : Pteriomorphia
Order : Ostreida
Superfamily : Pterioidea
Family : Hammer clams
Scientific name
Malleidae
Lamarck , 1818

The hammer shells (Malleidae) are a shell - Family from the order Ostreida . The oldest representatives of the hammer clams were found in deposits from the Miocene .

feature

The medium-sized to very large housings with a flattened cross-section are unevenly hinged and irregular in outline. They are usually greatly elongated in the dorsoventral direction and reach a height of up to 25 cm. The left flap is often slightly more arched than the right flap. The dorsal margin is usually very long, it can be up to 25 cm long. The front and rear edges can be extended, or just the rear edge. The housing roughly resembles a hammer in outline, hence the name hammer clams. The dorsoventral process (“stalk”) can be almost perpendicular to or at an angle to the dorsal margin. The edges of the case are usually wavy and have a slight gap. The lock is toothless. The ligament lies in a triangular ligament pit. On the dorsal side of the right valve in front of the ligament there is usually a slot for the byssus. The byssus can also be absent. There is only one large sphincter muscle. Usually the rear foot retractor muscle sits next to it or is fused with the sphincter muscle. The inner edge of the case is smooth.

The aragonitic shell is leafy on the outside and colored whitish or blackish. Inside, the shell is pearly . The ornamentation consists of strips parallel to the edge, which can be reinforced like ribs. The periostracum is thin, smooth, and well adherent.

Geographical distribution, habitat and way of life

The few recent species of hammer clams are mostly restricted to the tropical and subtropical seas. Malleus regula (Forsskål in Niebuhr, 1775) originally came as a Lesseps immigrant through the Suez Canal into the eastern Mediterranean .

The animals are mostly soft-bottom dwellers in shallow to somewhat deeper water ( Neoaviculovulsa coraliocola up to 280 m water depth), where they are attached to small stones or other bowls in the sediment with the help of the byssus . They are often stuck between coral sticks and in narrow crevices in rocky ground.

Taxonomy

The taxon was set up in 1818 by Jean-Baptiste de Lamarck as "les Malléacées". The name is widely accepted and has always been attributed to Lamarck. However, the size of the family as used in zoology and paleontology varied significantly. However, Thomas Waller removed most of the fossil species, as their shells are predominantly made of calcite. They also lack the inner layer of mother-of-pearl. He therefore transferred them to the Ostreida. For the genera excluded from the Malleidae, the family name Eligmidae Gill, 1871, which the Treatise had placed in the synonymy of Malleidae, is suitable . The position of this family is uncertain. Rüdiger Bieler and Paula M. Mikkelsen place them in the Pteriida , Michael Amler, but with question marks about the Ostreida . In 2006 Ilya Tëmkin took a middle position between the two extreme positions. He essentially excluded the Jurassic genera and some palaeogenic genera from the family, but left the genera Bouleigmus Basse, 1933 (Upper Cretaceous), Stefaniniella Tavani, 1939 (Upper Cretaceous), Vulsella Röding, 1798 (Paleocene to recent) and Vulsellina Raincourt, 1876 (Eocene) in the family Malleidae (next to the genus Malleus ). The stratigraphic range would change accordingly. In a later molecular biological work, however, he also excluded Vulsella from the Malleidae. It must be placed in the family Pteriidae.

The MolluscaBase therefore only provides the following taxa or only two genera to the family of hammer clams. Accordingly, the family's fossil record only dates back to the Miocene.

literature

  • Eugene V. Coan, Paul Valentich Scott, Frank R. Bernard: Bivalve Seashells of Western North America. Marine Bivalve Mollusks from Arctic Alaska to Baja California. Santa Barbara Museum of Natural History, Santa Barbara, CA 2012 ISBN 0-936494-30-1 , p. 222.
  • 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. 230/31)
  • Leo Georg Hertlein, Leslie Reginald Cox: Malleidae. In: Treatise on Invertebrate Paleontology, Part N Mollusca 6 (1): N326-N332, The University of Texas & Geological Society of America, 1969
  • Rudolf Kilias: Lexicon marine mussels and snails. 2nd edition, Verlag Eugen Ulmer, Stuttgart 1997 ISBN 3-8001-7332-8 (p. 182)

Individual evidence

  1. ↑ a b S. D. Gurumayum: The Malleidae (Mollusca: Bivalve) of India with a new distributional record of Malleus albus (Lamarck, 1819), from southeast cost of India-Nellore, Andhra Pradesh. Advances in Applied Science Research, 6 (8): 112-117, 2015 PDF
  2. ↑ Takashi Okutani, Tadashi Kusakari: An Unusual and New Malleid Bivalve from the Central Pacific. Venus - The Japanese journal of malacology, 46 (1), 1-5, 1987.
  3. ↑ Jean-Baptiste de Lamarck: Histoire naturelle des animaux sans vertèbres ... précédée d'une introduction offrant la détermination des caractères essentiels de l'animal, sa distinction du végétal et des autres corps naturels, enfin, l'exposition des principes fondamentaux de la zoologie. Self-published by the author, Paris 1815-1822. Online at www.biodiversitylibrary.org (p. 424)
  4. ↑ Thomas R. Waller: Jurassic Malleidae and the distinction between Ostreoida and Pterioida (Mollusca: Bivalvia). Journal of Paleontology, 59 (3): 768-769, 1985.
  5. ^ Rüdiger Bieler & Paula M. Mikkelsen: Bivalvia - a look at the branches . Zoological Journal of the Linnean Society, 148: 223-235, London 2006.
  6. ↑ Michael WW Amler: Synoptical classification of fossil and Recent Bivalvia. Geologica et Palaeontologica, 33: 237-248, Marburg 1999.
  7. ↑ Ilya Tëmkin: Morphological perspective on the classification and evolution of Recent Pterioidea (Mollusca: Bivalvia). Zoological Journal of the Linnean Society, 148: 253-312, 2006 PDF (Researchgate)
  8. ↑ Ilya Temkin: Molecular phylogeny of pearl oysters and Their relatives (Mollusca, Bivalvia, Pterioidea). BMC Evolutionary Biology, 10: 342, 28 pp., 2010 PDF .
  9. ↑ MolluscaBase: Malleidae Lamarck, 1818
  10. ↑ a b Maxime Glibert, Luc van de Poel: Les Bivalves fossiles du Cénozoïque Étranger des collections de l'Institut Royal des Sciences Naturelles de Belgique. II. Pteroconchida, Colloconchida, and Isofilibranchia. Institut Royal des Sciences Naturelles de Belgique / Koninklijk Belgisch Instituut voor Natuurwetenschappen, Mémoires / Verhandelingen, 2nd Série / Reeks, 78: 1-105, Brussels 1965 PDF (66 MB!)
  11. ↑ Julien Michel, Gaëlle Doitteau, Hakim Hebib, Pierre Lozouet, Loïc Villier: Biodiversity structure of an exceptionally preserved Aquitanian bivalve assemblage (Meilhan, SW France). New yearbook for geology and palaeontology treatises, 265/2: 113-130, Stuttgart 2012 PDF (Research guests )