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Echinoderms

Echinoderm
Temporal range: Cambrian-Holocene
Brockhaus and Efron Encyclopedic Dictionary b24 782-0.jpg
Echinoderm
Scientific classification
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Echinodermata
Bruguière, 1791 [ex Klein, 1734]
Subphyla and classes

HomalozoaGill & Caster, 1960

Homostelea
Homoiostelea
Stylophora
CtenocystoideaRobison & Sprinkle, 1969

Crinozoa

Crinoidea
ParacrinoideaRegnéll, 1945
Edrioasteroidea

Asterozoa

Ophiuroidea
Asteroidea

Echinozoa

Echinoidea
Holothuroidea
Ophiocistioidea
Helicoplacoidea
?Arkarua

Blastozoa

Blastoidea
Cystoideavon Buch, 1846
EocrinoideaJaekel, 1899

† = Extinct


HomalozoaGill & 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. One group of Cambrian echinoderms, the cinctans (Homalozoa), which are close to the base of the echinoderm origin, have been found to possess external gills used for filter feeding, like chordata and hemichordata.


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