Echinodermata has approximately 7000 described living species and about 13,000 extinct species known from the fossil record. This phylum is the largest without any freshwater or terrestrial forms.
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- Waggoner, B. 1999. "Introduction to the Echinodermata" (On-line). Accessed January 16, 2005 at http://www.ucmp.berkeley.edu/echinodermata/echinodermata.html.