Echinoderms

Echinoderms are a phylum of marine animals recognized by their five part radial body symmetry as adults, a body plan unlike almost any other animal group. The phylum includes sea stars, sea urchins, sand dollars, sea cucumbers, brittle stars, and feather stars, all moving and feeding through an internal water vascular system that operates rows of tube feet. Their skeleton is made of calcite plates embedded in the skin rather than an external shell, giving many species a spiny or leathery surface. Echinoderms are found on every ocean floor from shallow tide pools to the deep sea, and many species can regenerate lost arms or entire body sections.