An echinoderm is any member of the phylum Echinodermata (from Ancient Greek ἐχῖνος echīnos "hedgehog" and δέρμα derma "skin") of marine animals. The adults are recognizable by their (usually five-point) radial symmetry, and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone.

Echinodermata. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Echinoderm.