Limopsis, SASSI, 1827

Hickman, Carole S., 2023, Paleogene marine bivalves of the deep-water Keasey Formation in Oregon, Part II: The pteriomorphs, PaleoBios 40 (5), pp. 1-51 : 17-18

LIMOPSIS SASSI, 1827

Type species — By monotypy, Arca auritica Brocchi, 1814 . Miocene and Pliocene , Italy. Subsequently recognized living in the Mediterranean and Northeastern Atlantic .

There is no critical review of available genus-group names for limopsids. Tevesz (1977) recognized 17 available names based on species that are insufficiently well characterized to bear critical scrutiny. Beu (2006) documented 20 available names, in chronological order of their proposal, including seven proposed by Tom Iredale for living Australian species. Shells of the Iredale species are illustrated by Lamprell and Healey (1998). Anatomical and molecular data may require reassignment of some of these taxa to Crenellidae , Philobryidae , or Glycymerididae .

Although the type species is based on a Neogene fossil, it is widely recognized as a significant element in the living fauna of the Mediterranean and Northeastern Atlantic as far north as Norway and possibly the Arctic Ocean at depths ranging from 20 m to> 1000 m. Oliver and Allen (1980) provide detailed characterization of the anatomy and shell, ontogenetic variation in shell form, and observations of behavior and variation in shell orientation in different sediment types.

The geographic range of the type species is further extended by (dubious?) live reports from Antarctic, Subantarctic and Arctic faunas. The stratigraphic range of the type species was extended more than a century ago to Paleogene formations in Australia (Victoria and Tasmania) (Tate 1866). There is at least one additional fossil limopsid genus based on a species from the late Eocene of Australia ( Limarca Tate, 1886 ). Available genus-group names based on Cretaceous and Paleogene species are seldom used, but well-preserved shallow-marine Cretaceous limopsid shells are locally abundant and available for study in museum collections ( Squires 2012).

Taxonomic uncertainty provides strong justification for following the detailed treatment of Oliver (1981), who defined and classified the entire range of limopsid morphological and functional variation using Limopsis sesu lato . Conservative recognition of a single genus is increasingly appropriate and prevalent in modern treatments of the diversity of fossil species in the high-latitude southern hemisphere (e.g., Beu 2006, Wittle et al. 2011).

Stratigraphic range —Middle Jurassic–Holocene.