Scientific Classification

The word echinoderms derived from the word Echinodermata, meaning "spiny skin" in Greek. There are five classes in the Echinodermata phyla. The sea stars are the Asteroideas (true sea stars and sun stars), Ophiuroideas (brittle stars and basket stars). Many authorities commonly group them into one class, the Asterozoa (or Stelleroidea). Crinoidea (feather stars and sea lilies), Holothuroidea (sea cucumbers), and Echinoidea (sea urchins, heart urchins, and cake urchins, or sand dollars) are the other three. Ophiuroideas have the most in their group with about 2,000 species. Crinoideas have the least number of species with only about 650 species.