The animal group Echinoderms, which contains about 7000 species, gets its name from Greek, literally meaning "spiny skin." Many echinoderms actually do have spiny skin, but others do not. This group exists exclusively in the sea, and cannot be found on land or in fresh water. All echinoderms have one thing in common, they are all radially semeterical. This means that the creatures have appendages (aka. limbs) which point outward from the center of the body like the spokes on a bike wheel. Also, these limbs usually occur in multiples of five, although there are a few exceptions. There are several well known members of this group, like starfish and sea urchins. The radial symmetry is obvious in these creatures.

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