The members of phylum Echinodermata are spiny-bodied sea creatures which possess an endoskeleton (internal skeleton) composed of calcareous ossicles (small bones), embedded in the skin. Echinoderms are exclusively marine, bottom-dwelling and free-living animals. They are triploblastic coelomates, which have an organ-system level of organization and unsegmented bodies. The adult forms are radially symmetrical, while their larvae are bilaterally symmetrical.
The digestive system in echinoderms is complete with two separate openings. It lies along the dorsoventral axis of the body; the mouth lies on the lower (ventral) side and anus on the upper (dorsal) side of the body. Aristotle’s lantern is a masticatory apparatus in the members of Class Echinoidea (sea urchins) - Echinus (sea urchin), Echinocardium (heart urchin), and Clypeaster. It is a complex dental apparatus in the mouth of such animals. The teeth of Aristotle’s lantern are extruded to scrape algae and other food from rocks.
