Starfish belong to an older animal group-echinoderms. Echinoderms (animals with spines on their epidermis) also include sea urchins and sea cucumbers, which originally originated in the early Cambrian about 55 million years ago and have not changed much since then. Different from mollusks and insects, echinoderms have endoskeleton, which is composed of bone plates and mainly composed of calcium carbonate. This feature makes them have a direct kinship with all vertebrates, including humans.