Sea stars are echinoderms belonging to the class Asteroidea. The names “sea star” and “starfish” are sometimes differentiated, with “starfish” used in a broader sense to include the closely related brittle stars, which make up the class Ophiuroidea, as well as excluding sea stars which do not have five arms (have Many arms), such as the sun stars and cushion stars.
Sea stars exhibit a superficially radial symmetry. They typically have five “arms” which radiate from a central disk (pentaradial symmetry). However, the evolutionary ancestors of echinoderms are believed to have had bilateral symmetry. Sea stars do exhibit some superficial remnant of this body structure, evident in their larval pluteus forms.
