Claim: Edrioasteroidea, an extinct class of echinoderms that resembled a symmetrical disc or cushion, has a main feature wherein it consists of five arms or ambulacra in the body wall radiating outwards from the central mouth wherein its ambulacra grew either curved or straight.
Evidence: Edrioasteroidea is an extinct class of echinoderms. The living animal would have resembled a pentamerously symmetrical disc or cushion. The main feature consisted of five arms, or ambulacra, in the body wall radiating outwards from the central mouth. The ambulacra grew either curved or straight.