Frigidocardium thaanumi ( Pilsbry, 1921 )

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 72

Frigidocardium thaanumi ( Pilsbry, 1921)

Figures 36 F–G

Cardium thaanumi Pilsbry, 1921: p. 232 , pl. 12, fig. 24.

Microcardium thaanumi ( Pilsbry, 1921) — Dall et al., 1938: p. 153, pl. 41, figs. 5–8.

Nemocardium thaanumi ( Pilsbry, 1921) — Kay, 1979: p. 555, pl. 180, figs. H–I.

Frigidocardium thaanumi ( Pilsbry, 1921) — Tröndlé & Boutet, 2009: p. 9; Huber, 2010: p. 307, fig. 7; Severns, 2011: p. 474, pl. 217, fig. 2.

Material examined. One single RV (BK).

Diagnosis. Shell small, nearly hemispherical, equivalve, thin and very fragile. Umbo strongly elevated. Sculpture homogenous, exterior surface covered by numerous fine radiating threads which are crossed by even finer commarginal threads. Margins minutely crenulated. Hinge narrow, consisting of subequal erect cardinals and elongated laterals. Color translucent white and irregularly streaked with orange rays.

Remarks. A single RV was dredged at 150 m, with a size of 4 mm, but is now largely destroyed. The illustrated, a very juvenile specimen, conforms by its quadrate shape, fragile structure, fine radial sculpture, orangewhite color and by its hinge with that of F. thaanumi . Frigidocardium thaanumi is a small species, reaching 12 mm in the Hawaiian Islands and 18.4 mm in the Marquesas Islands. The depth range is 15– 200 m. J.J. ter Poorten, (pers. comm., 2010) confirmed the identity.

Habitat. Dredged at 150 m in fine sand and mud, off the western coastline near Tahai.

Distribution. Frigidocardium thaanumi was originally described from the Hawaiian Islands, but is also known from the Marquesas Islands and now Easter Island as well— E4.