Giant Deep Sea Oyster

Radiocarbon dating reveals that individuals reach an astounding lifespan of 100 to 500 years, placing them among the longest lived molluscs (and animals) known to date

Shell large (up to ca. 20 cm dorso-ventrally, to over 12 cm antero-posteriorly), cemented to substrate by the left valve which is slightly larger and thicker than the right valve; ventral margin of both valves growing roughly parallel to the attachment surface and not making a distinct angle with it. Shell material brittle and light-weighted due to extensive vesicular structure. Beaks moderately prominent and nearly orthocline, with a triangular ligamental area; a most unusual feature in ths species is that the central part of the ligament (resilium) is very narrow and does not protrude at all over the hinge line, which us straight. Inside of shell with solid endostracum occupying about half the total height; scar of adductor muscle unusually small and situated closer to the hinge line than to the ventral edge of the endostracum. Commissural edge next to the hinge line provided by well developed chomata of the so-called "neopycnodontine" type. Exterior of valve devoid of sculpture other than scale-shaped remnants of the shell margins, pale buff in colour.

Currently known from the Azores (type locality in Faial Channel) Bay of Biscay, and the Ibero-Moroccan area at depths of ca. 500 m