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Echinodermata (phylum)
Nota de aplicación
Phylum having members that are characterized by a hard, spiny covering or skin. Echinoderms have existed since the Lower Cambrian Period, and today comprise about extant 7,000 species that fall into five well-defined groups: Crinoidea (sea lilies and feather stars), Ophiuroidea (basket stars and brittle stars), Asteroidea (starfishes), Echinoidea (sea urchins, sand dollars, and sea biscuits), and Holothuroidea (sea cucumbers). In the 19th century…
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