Spondylus gaederopus, the common name being European thorny oyster, is an edible marine bivalve mollusk belonging to the family Spondylidae. This species is found in the Black Sea, in the Mediterranean and in the adjacent Atlantic.
This oyster has a reddish-purple shell reaching a length of 2.4 to 2.9 inches, covered with long, flat, and irregularly arranged spines. The two parts of the shells are hinged together with a ball and socket type hinge, rather than a toothed hinge as is more commonly seen in other bivalves. These mollusks have a number of eyes around the edges of the shell.
They reside in shallow water and on the rocky seabed at a depth of roughly 50 meters. The colonies of this common mollusk declined in the early 1980’s for unknown reasons.
Image Caption: Bivalvia. Credit: Bricktop/Wikipedia(CC BY-SA 3.0)