; class Stelleroidea, subclass Asteroidea)
An order of starfish in which the mouth angle plates are large and derived from fused ambulacral ossicles. Marginal ossicles are not invariably developed, but commonly bear dorsoventral, intermarginal fascioles. The marginals are separated from the mouth frame by small, oral, intermediate ossicles. The order is known from the Ordovician to the present.
Subjects: Zoology and Animal Sciences.