Cardiomya, A. Adams, 1864

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 : 12-14

CARDIOMYA A. Adams, 1864

Type species —By monotypy, Neaera gouldiana Hinds, 1843 . Holocene, Japanese Seas.

Features of the hingeline and anatomy are required for allocation to some of the cuspidariid genera, but Cardiomya has been used consistently for both fossil and living inflated rostrate species with strong radial ribbing on the shell. The ribbing differentiates them from similarly shaped rostrate shells of Cuspidaria Nardo, 1840 and other genera that are smooth or have only co-marginal striae or ribs.

Some of the Pacific Coast Cenozoic species were originally described under Cuspidaria (or Neaera Gray in Griffith and Pidgeon 1833, an earlier name preoccupied by a dipteran insect genus). It is fortunate that the Cenozoic species all have radial ribbing and cannot be confused with the smooth shells of Cuspidaria or smooth-shelled species assigned to Neaera under its tangled history of misspellings ( Stewart 1930, p. 307–308, Petit and Coan 2008, p. 228).

Species of Cardiomya in the Pacific Coast Eocene have been distinguished initially by the presence or absence of radial ribbing on the rostrum. Second-order features include relative length and width of the rostrum, the number and comparative strength of radial ribs on the disc, presence or absence of “inter-ribs” on the disc, and the shape, strength and number of ribs on the rostrum.

Although the shells are thin and fragile, the shallow infaunal life habit appears to have conferred some advantage in preservation by rapid burial. Fossil specimens are typically double-valved and are not crushed, although the

valves may be partially separated.

Stratigraphic range —Cretaceous to Holocene.