Author: Jan Scholten
Name: Echinodermata means spiny skin; from echinos meaning sea-urchin, originally hedgehog and derma menaing skin.
Habitat: marine aquatics; at every ocean depth, from the intertidal zone to the abyssal zone; no freshwater or terrestrial representatives.
Genera: 7000 species.
They are starfish, sea urchins, sand dollars, sea cucumbers. They usually have afive-point, bilateral symmetry; remarkable regeneration of tissue, organs, limbs, complete regeneration from a single limb; asexual reproduction; ossified skeletons, contributors to many limestone formations; maybe the radiation of echinoderms was responsible for the Mesozoic revolution of marine life.
2 Eleutherozoa, motile
2.1 Asteroidea: starfish
2.2 Ophiuroidea: brittle stars.
2.3 Echinoidea: sea urchins and sand dollars.
2.4 Holothuroidea: sea cucumbers
3 Pelmatazoa: crinoids, sessile; the feather stars, have secondarily re-evolved a free-living lifestyle.
5. Concentricycloidea: sea daisies
Ophiuroidea: Ophiuroids are members of the class Ophiuroidea, which includes brittle stars and basket stars. Both brittle and basket stars are somewhat similar to sea stars in that they have multiple arms attached to a central disk. It is known about 1900 species. They do not have breathing and excretive systems and they can regenerate lost arms.
Asteroidea: Sea stars