List of animal phyla
Echinodermata: One of the most important marine phyla, with radial symmetry. 17,000 living species, which all live in the ocean, mostly on the sea bed. This is the largest phylum which is entirely marine. The main classes are quite well-known. The Crinoids are 'sea lilies', a remnant of a once great clade; the Asterozoa are the starfish, major predators of shell-fish, and the brittle stars. The Echinozoa are the sea urchins, sand dollars and the sea cucumbers. There are also some extinct groups. The echinoderm fossil record is extensive. Larvae are varied and planktonic: pluteus (echinoids); dipleurula, then bipinneria; then brachiolaria (starfish); ophiopluteus (brittle stars); doliolaris (sea cucumbers).