echinoderm

noun

1. any marine animal of the invertebrate phylum Echinodermata, having a radiating arrangement of parts and a body wall stiffened by calcareous pieces that may protrude as spines and including the starfishes, sea urchins, sea cucumbers, etc.

noun

1. any of the marine invertebrate animals constituting the phylum Echinodermata, characterized by tube feet, a calcite body-covering (test), and a five-part symmetrical body. The group includes the starfish, sea urchins, and sea cucumbers

n.

1835, from Modern Latin Echinodermata, name of the phylum that includes starfish and sea urchins, from Greek ekhinos “sea urchin,” originally “porcupine, hedgehog” (see echidna) + derma (genitive dermatos) “skin” (see derma); so called from its spiky shell.

1. Any of various marine invertebrates of the phylum Echinodermata, having a latticelike internal skeleton composed of calcite and usually a hard, spiny outer covering. The body plans of adult echinoderms show radial symmetry, typically in the pattern of a five-pointed star, while the larvae show bilateral symmetry. Echinoderms probably share a common ancestor with the hemichordates and chordates, and were already quite diversified by the Cambrian Era. They include the starfish, sea urchins, sand dollars, holothurians (sea cucumbers), and crinoids, as well as thousands of extinct forms.