<P> The scientific name Asteroidea was given to starfish by the French zoologist de Blainville in 1830 . It is derived from the Greek aster , ἀστήρ ( a star ) and the Greek eidos , εἶδος ( form , likeness , appearance ) . The class Asteroidea belongs to the phylum Echinodermata . As well as the starfish , the echinoderms include sea urchins , sand dollars , brittle and basket stars , sea cucumbers and crinoids . The larvae of echinoderms have bilateral symmetry , but during metamorphosis this is replaced with radial symmetry , typically pentameric . Adult echinoderms are characterized by having a water vascular system with external tube feet and a calcareous endoskeleton consisting of ossicles connected by a mesh of collagen fibres . Starfish are included in the subphylum Asterozoa , the characteristics of which include a flattened , star - shaped body as adults consisting of a central disc and multiple radiating arms . The subphylum includes the two classes of Asteroidea , the starfish , and Ophiuroidea , the brittle stars and basket stars . Asteroids have broad - based arms with skeletal support provided by calcareous plates in the body wall while ophiuroids have clearly demarcated slender arms strengthened by paired fused ossicles forming jointed `` vertebrae '' . </P>
<P> The scientific name Asteroidea was given to starfish by the French zoologist de Blainville in 1830 . It is derived from the Greek aster , ἀστήρ ( a star ) and the Greek eidos , εἶδος ( form , likeness , appearance ) . The class Asteroidea belongs to the phylum Echinodermata . As well as the starfish , the echinoderms include sea urchins , sand dollars , brittle and basket stars , sea cucumbers and crinoids . The larvae of echinoderms have bilateral symmetry , but during metamorphosis this is replaced with radial symmetry , typically pentameric . Adult echinoderms are characterized by having a water vascular system with external tube feet and a calcareous endoskeleton consisting of ossicles connected by a mesh of collagen fibres . Starfish are included in the subphylum Asterozoa , the characteristics of which include a flattened , star - shaped body as adults consisting of a central disc and multiple radiating arms . The subphylum includes the two classes of Asteroidea , the starfish , and Ophiuroidea , the brittle stars and basket stars . Asteroids have broad - based arms with skeletal support provided by calcareous plates in the body wall while ophiuroids have clearly demarcated slender arms strengthened by paired fused ossicles forming jointed `` vertebrae '' . </P>
what type of symmetry does a sea star have
what type of symmetry does a sea star have
radial symmetry
radial symmetry