Thracia keaseyensis Hickman, 2014

Carole, Hickman, S. & Ca, 2014, Paleogene marine bivalves of the deep-water Keasey Formation in Oregon, part IV: The anomalodesmatans, PaleoBios 31 (3), pp. 1-21 : 8-9

PERIPLOMATIDAE Dall, 1895

As noted under Thraciidae , periplomatids also have Mesozoic origins. Although they are never abundant as fossils, crushed and diagenetically altered specimens are easily recognized by a combination of inner sheet nacre and retained co-marginal undulations. The paucity of fossil periplomatid specimens in southern South America has been attributed to a combination of habitat specialization and non-preservation of the fragile shell ( Griffin and Pastorino 2006). Considering the Cenozoic record in northwestern North America, especially in the fine-grained deep-water facies, I conclude that low population density is most likely responsible for paucity of fossils of a species that is rare at many localities. In addition, crushed specimens are difficult to collect intact and require special care when encountered in the field.

Stratigraphic range— Upper Jurassic (Tithonian) to

Holocene.