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Temporal range: Lower Ordovician–Recent
Anadara from the Pliocene of Cyprus.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Subclass: Pteriomorphia
Order: Arcida

11, See text.



The Arcida is an extant order of bivalve molluscs.[1] This order dates back to the lower Ordovician period. They are distinguished from related groups, such as the mussels, by having a straight hinge to the shells, and the adductor muscles being of equal size.[2] The duplivincular ligament, taxodont dentition, and a shell microstructure consisting of the outer crossed lamellar and inner complex crossed lamellar layers are defining characters of this order.[3]

Seven families are currently recognised within the order, including the well-known ark clams or ark shells in the family Arcidae.


The order Arcida, as the suborder Arcacea, is included in the order Taxodonta by R.C. Moore, 1952,[4] characterised by simple hinge-line dentition consisting of small, numerous, similar hinge teeth, separate mantle lobes, poorly developed siphons, and filibranch gills.

In 2010, Bieler, Carter & Coan[5] proposed a new classification system for the Bivalvia which combines the taxodont Arcida with the dysodont Limida Mytilida, Ostreida and Pteriida as the Pteriomorphia. Subtaxa included in the Arcida are shown below.

In 2016, the superfamilies of Arcida changed from two to three, with an additional superfamily of fossils only. The new taxonomy is as follows:[1][5]

  • Superfamily Arcoidea Lamarck, 1809[6]
  • Superfamily Glyptarcoidea Cope, 1996†:[7][8][9] with fossil species only.
    • Family Glyptarcidae Cope, 1996
    • Family Pucamyidae Sánchez & Benedetto, 2007
  • Superfamily Limopsoidea Dall, 1895[10]


  1. ^ a b Bieler, Rüdiger; Gofas, Serge (2016-02-07). "Arcoida Stoliczka, 1871". WoRMS. World Register of Marine Species. Retrieved 2017-01-15.
  2. ^ Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 430. ISBN 978-0-03-056747-6.
  3. ^ Matsumoto, M. (2003). "Phylogenetic analysis of the subclass Pteriomorphia (Bivalvia) from mtDNA COI sequences". Molecular Phylogenetics and Evolution. 27 (3): 429–440. doi:10.1016/S1055-7903(03)00013-7. PMID 12742748.
  4. ^ R.C, Moore, Pelecypods, Ch 10, Inverrtebrate Fossils, Moore, Lalicker, and Fischer. McGraw-Hill, 1952.
  5. ^ a b Bieler, R.; Carter, J.G.; Coan, E.V. (2010). "Classification of Bivalve families". In Bouchet, P.; Rocroi, J.P. (eds.). Nomenclator of Bivalve Families. Vol. 52. pp. 113–133. doi:10.4002/040.052.0201. S2CID 86546840. ((cite book)): |journal= ignored (help)
  6. ^ Gofas, Serge (2010-07-09). "Arcoidea Lamarck, 1809". WoRMS. World Register of Marine Species. Retrieved 2017-01-15.
  7. ^ Lemer, S.; González, V.L.; Bieler, R.; Giribet, G. (2016). "Cementing mussels to oysters in the pteriomorphian tree: a phylogenomic approach". Proceedings of the Royal Society B: Biological Sciences. 283 (20160857): 20160857. doi:10.1098/rspb.2016.0857. PMC 4936043. PMID 27358369.
  8. ^ Decock, Wim (2015-01-29). Bouchet, Philippe (ed.). "Glyptarcoidea Cope, 1996". WoRMS. World Register of Marine Species. Retrieved 2017-01-15.
  9. ^ Cope, J. C. W. (1996). "Early Ordovician (Arenig) bivalves from the Llangynog inlier, South Wales". Palaeontology. 39 (4): 979–1025, pl. 1–7.
  10. ^ Gofas, Serge (2010-07-09). "Limopsoidea Dall, 1895". WoRMS. World Register of Marine Species. Retrieved 2017-01-15.
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