The Gryphaeidae, common name the foam oysters or honeycomb oysters, are a family of marine bivalve mollusks. This family of bivalves is very well represented in the fossil record, however the number of living species is very few.
All species have shells cemented to a substrate. Shells are considered brittle, inequivalve, with the left, lower (cemented) valve convex and the right (upper, non-cemented) valve flat or slightly concave.
Subfamilies Genera and species within this family are divided into three subfamilies, Exogyrinae, Gryphaeinae and Pycnodonteinae. Both Exogyrinae and Gryphaeinae are completely extinct. Only two genera Hyotissa and Neopycnodonte in the subfamily Pycnodonteinae have extant species.
Genera and species Genera and species within the family Gryphaeidae include: Family Gryphaeidae Vialov, 1936 (some genera also known as Devil's toenails) Subfamily †Exogyrinae Vialov, 1936 Genus †Aetostreon Bayle, 1878 Genus †Amphidonte Fischer von Waldheim, 1829 Genus †Costagyra Vialov, 1936 Genus †Exogyra Say, 1820 Genus †Fluctogyra Vialov, 1936 Genus †Gryphaeostrea Conrad, 1865 Genus †Gyrostrea Mirkamalov, 1963 Genus †Ilymatogyra Stenzel, 1971 Genus †Nanogyra Beurlen, 1958 Genus †Nutogyra Vialov, 1936 Genus †Planospirites Lamarck, 1801 Genus †Vultogryphaea Vialov, 1936 Subfamily †Gryphaeinae Vialov, 1936 Genus †Africogryphaea Freneix, 1963 Genus †Deltoideum Rollier, 1917 Genus †Gryphaea Lamarck, 1801 Genus †Liostrea DouvillŽ, 1904 Genus †Pernostrea Munier-Chalmas, 1864 Genus †Praeexogyra Charles, 1952 Subfamily Pycnodonteinae Stenzel, 1959 Genus †Gigantostrea (Sacco, 1897) Genus Hyotissa Stenzel, 1971 Genus †Labrostrea Vialov, 1936 Genus Neopycnodonte Stenzel, 1971 Genus †Pycnodonte (Fischer von Waldheim, 1835) Genus †Texigryphaea Stenzel, 1959 Subfamily Incertae sedis Genus †Rhynchostreon Bayle, 1878
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