Clypeaster

Clypeaster, common name 'cake urchins' or 'sea biscuits', is a genus of echinoderms belonging to the family Clypeasteridae. The genus name Clypeaster is derived from the Latin “clypeus” (meaning round shield) and “aster” (meaning star), with reference to the shape of these organisms. Genus Clypeaster includes irregular sea urchins with a bilateral symmetry (Bilateria). They have a rounded pentagonal outline. The anus of these large burrowing cake urchins has migrated from the apical disc to the oral side, on the lower surface. Besides this development, the mouth has moved in the center of the base and the body has flattened. These changes accompany a change in lifestyle, as by day they live partially or completely buried in sand in shallow waters and emerge at night to feed on the sediment. This genus has a worldwide distribution. Fossils can be found from late Eocene (33.9–37.2 mya) to Recent age. Clypesater is a typical form of shallow waters of tropical areas.