the freely swimming larva of starfish; it has two flickering whips (fins). Like other dipleurulas, it is bisymmetrical and has three pairs of coeloms. Bipinnaria turns into Brachiolaria. Its morphology is similar to that of other invertebrates (such as marine bristle worms, Enteropneusta, and Pogonophora), which suggests the derivation of these groups from a common ancestor.