echinodermata defined in 1951 yearechinodermata - echinodermata;
echinodermata - Phylum of animals containing sea-urchins, sea-cucumbers, starfish, brittle-stars, feather-stars, and sea-lilies. Marine; more or less radially symmetrical (with usually five axes of symmetry); calcareous skeletal plates in the skin; tube feet; coelom well developed, consisting of several intricate spaces, one of which is the water vascular system; larva (when present) more or less bilaterally symmetrical with coelom in three segments. Their mode of development shows them to be related to the same stock that gave rise to vertebrates. Includes classes Asteroidea, Ophiur-oidea, Echinoidea, Holothuroidea, Grinoidea. Palaeozoic rocks contain remains of several other groups of echinoderms now extinct; they were mostly sedentary forms. It seems that modern free-living echinoderms were derived from radially symmetrical sedentary forms.
near echinodermata in Knolik
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