Echinodermata

Echinoderm Temporal range: Cambrian-Holocene
Echinoderm
Scientific classification
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Superphylum:	Deuterostomia
Phylum:	Echinodermata Bruguière, 1791 [ex Klein, 1734]
Subphyla and classes
Homalozoa † Gill & Caster, 1960 Homostelea † Homoiostelea † Stylophora † Ctenocystoidea † Robison & Sprinkle, 1969 Crinozoa Crinoidea Paracrinoidea † Regnéll, 1945 Edrioasteroidea † Asterozoa Ophiuroidea Asteroidea Echinozoa Echinoidea Holothuroidea Ophiocistioidea † Helicoplacoidea † ?Arkarua † Blastozoa † Blastoidea † Cystoidea † von Buch, 1846 Eocrinoidea †Jaekel, 1899 † = Extinct

Homalozoa † Gill & Caster, 1960

Crinozoa

Asterozoa

Echinozoa

Blastozoa †

† = Extinct

Echinoderm is the common name given to any member of the phylum Echinodermata (from Ancient Greek, ἐχῖνος, echinos – "hedgehog" and δέρμα, derma – "skin") of marine animals. The adults are recognizable by their (usually five-point) radial symmetry, and include such well-known animals as sea stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). Echinoderms are also the largest phylum that has no freshwater or terrestrial (land-based) representatives.

Aside from the hard-to-classify Arkarua (a Precambrian animal with echinoderm-like pentamerous radial symmetry), the first definitive members of the phylum appeared near the start of the Cambrian.

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