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• Image Gallery
Echinoderms
Echinoderms (ee-KINE-oh-derms) have internal skeletons made of hard plates usually covered with spines. These spines often give echinoderm skin a prickly appearance.
Many echinoderms have another unique characteristic: their bodies are divided into five symmetrical parts. Think of a sea star (or “starfish”) with five “arms” (although they can have as many as ten or fifteen arms.)
Sea stars and sea lilies (crinoids), both echinoderms, first evolved in the Ordovician Period. Sea lilies—which look like flowers, but are animals—have clusters of “arms” branching off a central “stalk” in multiples of five.
Continue to Worm, Chordate, and Algae Images. >>
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