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(For the tree oyster mushroom, see Pleurotus ostreatus.)

Temporal range: Permian - Recent
Tide pool shells in Kona 2.jpg
Live Isognomon sp. under a rock in Kona District, Hawaii
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Pterioida
Family: Pteriidae
Genus: Isognomon
Lightfoot, 1786
Type species
Ostrea perna Linnaeus, 1767

See text.

  • Isognoma Lightfoot, 1786 (Isognoma is an alternative original spelling for Isognomon)
  • Isognomon (Anisoperna) Iredale, 1939
  • Isognomon (Isognomon) Lightfoot, 1786
  • Isognomon (Melina) Philipsson, 1788
  • Isogonum Röding, 1798
  • Malleoperna Iredale, 1939
  • Melina Philipsson, 1788
  • Parviperna Iredale, 1939
  • Pedalion Dillwyn, 1817
  • Perna Bruguière, 1789
  • Pernaria Rafinesque, 1815
  • Sutura Megerle von Mühlfeld, 1811

Isognomon is a genus of marine bivalve mollusks which is related to the pearl oysters.[1]

Isognomon is known in the fossil record from the Permian period to the Quaternary period (age range: 254.0 to 0.012 millions years ago). Fossils of species within this genus have been found all over the world. [2]


This genus was formerly placed in the family Isognomonidae, however molecular phylogeny studies have shown that these tree oysters belong in the family Pteriidae.[3]


These oysters grow to be about 4.75 inches (12.1 cm) in overall length, producing a highly irregular shell with a blue-gray and often heavily encrusted exterior but a smooth and pearly white interior. They use their byssus to completely immobilize themselves to the roots of mangrove trees, corals, and other substrates.[4] It is because of the preference for mangroves that these are sometimes called tree oysters[5]


Extinct species[edit]

Fossil of Isognomon maxillatus from Pliocene of Italy

Extinct species within this genus include: [2]

  • Isognomon gariesensis Kensley and Pether 1986
  • Isognomon gaudichaudi d'Orbigny 1842
  • Isognomon isognomoides Stahl 1824
  • Isognomon isognomon Linnaeus 1758
  • Isognomon isognomonoides Stahl 1824
  • Isognomon legumen Gmelin 1790
  • Isognomon maxillatus Lamarck 1819
  • Isognomon nucleus Lamarck 1819
  • Isognomon quadrisulcata Ihering 1897
  • Isognomon valvanoi Rossi de Garcia and Levy 1977
Species brought into synonymy
  • Isognomon acutirostris (Dunker, 1869): synonym of Isognomon nucleus (Lamarck, 1819)
  • Isognomon anomioides (Reeve, 1858): synonym of Isognomon australica (Reeve, 1858)
  • Isognomon aviculare (Lamarck, 1819): synonym of Isognomon isognomum (Linnaeus, 1758)
  • Isognomon brevirostre Link, 1807: synonym of Isognomon isognomum (Linnaeus, 1758)
  • Isognomon dentifer (Krauss, 1848): synonym of Isognomon nucleus (Lamarck, 1819)
  • Isognomon isognomon (Linnaeus, 1758): synonym of Isognomon isognomum (Linnaeus, 1758)
  • Isognomon roberti Koch, 1953: synonym of Isognomon perna (Linnaeus, 1767)
  • Isognomon rude (Reeve, 1858): synonym of Isognomon isognomum (Linnaeus, 1758)
  • Isognomon rupella (Dufo, 1840): synonym of Isognomon nucleus (Lamarck, 1819)
  • Isognomon sulcatum Lamarck: synonym of Isognomon perna (Linnaeus, 1767)
  • Isognomon vulsella (Lamarck, 1819): synonym of Isognomon legumen (Gmelin, 1791)


  1. ^ Isognomon Lightfoot, 1786.  Retrieved through: World Register of Marine Species on 12 March 2011.
  2. ^ a b Fossilworks
  3. ^ Temkin, I. (2010) Molecular phylogeny of pearl oysters and their relatives (Mollusca, Bivalvia, Pterioidea), BMC Evolutionary Biology 10:342
  4. ^ Arthur Peter Hoblyn Oliver (2004). Guide to Seashells of the World. Firefly. p. 300. ISBN 978-1-55297-943-3. 
  5. ^ Papuaweb Archived 2012-10-17 at the Wayback Machine.
  • Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 180–213
  • Huber M. (2010) Compendium of bivalves. A full-color guide to 3,300 of the world’s marine bivalves. A status on Bivalvia after 250 years of research. Hackenheim: ConchBooks. 901 pp., 1 CD-ROM
  • Coan E.V. & Valentich-Scott P. (2012) Bivalve seashells of tropical West America. Marine bivalve mollusks from Baja California to northern Peru. 2 vols, 1258 pp. Santa Barbara: Santa Barbara Museum of Natural History.