Arca Linnaeus, 1758.
Geological range: Middle Jurassic to Recent (source: Cox et al., 1969, Treatise N251-252). The Paleobiology Database reports the genus extending into the Permian and Triassic.
Geographic distribution: A distributional map for modern Arca may be accessed from OBIS. A distributional map for ancient Acar may be accessed from the Paleobiology Database (Primary data contributors: Hendy, A. J. W., W. Kiessling, and A. I. Miller.).
Diversity: The WoRMS database recognizes 22 species of extant Arca (unvetted). The Paleobiology Database recognizes 195 species from the fossil record (unvetted) (Primary data contributors: Hendy, A. J. W., W. Kiessling, and A. I. Miller.); WWoRMS recognizes an additional 7 species (202 total).
Paleoecology: All species of Arca are epifaunal, sedentary (can reposition), bysally attached suspension feeders. Source: Todd (2015).
Phylogenetic status: Paraphyletic. A recent molecular phylogenetic analysis by Combosch and Giribet (2016) does not supports the monophyly of Arca, as one extant species, Arca boucardi, is sister to the family Cucullaeidae.