Echinoderm - Any member of the phylum Echinodermata, a group of exclusively marine animals that have a water-vascular system, which circulates water and assists them in both feeding and locomotion. Examples of echinoderms include sea urchins, star fish, brittle stars, sea cucumbers, heart urchins, sand dollars, cystoids, blastoids, and crinoids.

marine invertebrates with tube feet and calcite-covered five-part radially symmetrical bodies

a kind of sea animal with spiny skin

A class of spiney-shelled invertebrate marine animals, characterised by an internal skeleton of porous calcite plates