Sea urchins belong to the phylum Echinodermata (common name Echinoderm), which also include sea stars and sea cucumbers. There are approximately 7000 described species of Echinoderms living only in marine environments.
Sea urchins belong to the phylum Echinodermata (common name Echinoderm), which also include sea stars and sea cucumbers. There are approximately 7000 described species of Echinoderms living only in marine environments.