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Article: Echinoderm
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- Biology
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CopyrightCOPYRIGHT 2002 The Gale Group Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Echinoderm
The echinoderms (
echino
means "spiny;"
derm
means "skin") are large, conspicuous, entirely marine invertebrates. Today, this group inhabits virtually every conceivable oceanic environment, from sandy beaches and coral reefs to the greatest depths of the sea. They are also common as fossils dating back 500 million years. These less-familiar fossil types are represented by a bizarre variety of animals, some of which reveal their relationship to the living echinoderms only at close inspection.
Diversity
The species living today are generally regarded as belonging to five subgroups: sea lilies and feather stars (Crinoidea, 650 species); starfish (Asteroidea, 1,500 species), ...