Echinoderms are a phylum of marine animals found at all depths. This phylum contains about 7,000 living species and 13,000 extinct ones. These animals are represented by the sea star, sea cucumber, and the sea urchins. Echinodermata is the largest animal phylum to lack any freshwater or terrestrial representatives.

 

Photographed by Adrian Pingstone in December 2005 and released to the public domain.