, early
Campanian), near
Amman, Jordan Shell sculpture tends to be primarily concentric, but radial and
divaricating ornamentation (see
Gafrarium), and rarely spines (
Pitar lupanaria for example) occur on some. One small subfamily, the Samarangiinae, is created for a unique and rare clam found in coral reefs with an outer covering of cemented sand or mud that texturally camouflages it while enhancing the thickness of the shell. Several venerid clams have overall shell shapes adapted to their environments.
Tivela species, for example, have the triangular outline of the surf clams in other bivalve families, and occur often in surf zones. Some
Dosinia species are almost disc-like in shape and reminiscent of lucinid bivalves; both types of circular bivalves tend to burrow relatively deeply into the sediment. Further reclassification is to be expected as the results of current research in
molecular systematics on the group appear in the literature. Venerids have rounded or oval solid shells with the umbones (projections) inturned towards the anterior end. Three or four cardinal teeth are on each valve. The
siphons are short and united, except at the tip, and are not very long. The foot is large. == References ==