| Echinoderms | |
|---|---|
| |
| Extant and extinct echinoderms of six classes: Fromia indica (Asteroidea); Ophiocoma scolopendrina (Ophiuroidea); Stomopneustes variolaris (Echinoidea); Oxycomanthus bennetti (Crinoidea); Actinopyga echinites (Holothuroidea); Ctenocystoidea. | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Clade: | ParaHoxozoa |
| Clade: | Bilateria |
| Clade: | Nephrozoa |
| Superphylum: | Deuterostomia |
| Clade: | Ambulacraria |
| Phylum: | Echinodermata Bruguière, 1791 [ex Klein, 1734] |
| Type genus | |
| Echinus Linnaeus, 1758
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| Subphyla and classes | |
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See taxonomy | |
An echinoderm (/ɪˈkaɪnəˌdɜːrm, ˈɛkə-/)[2] is any animal of the phylum Echinodermata (/ɪˌkaɪnoʊˈdɜːrmətə/), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies".[3] While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry (pentamerous symmetry), and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
The echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the biotic desert of the deep sea, as well as shallower oceans. Most echinoderms are able to reproduce asexually and regenerate tissue, organs and limbs; in some cases, they can undergo complete regeneration from a single limb. Geologically, the value of echinoderms is in their ossified dermal endoskeletons, which are major contributors to many limestone formations and can provide valuable clues as to the geological environment. They were the most used species in regenerative research in the 19th and 20th centuries. Further, some scientists hold that the radiation of echinoderms was responsible for the Mesozoic Marine Revolution.
- ^ Smith, A., Zamora, S. & Álvaro, J. The oldest echinoderm faunas from Gondwana show that echinoderm body plan diversification was rapid. Nat Commun 4, 1385 (2013). https://doi.org/10.1038/ncomms2391.
- ^ "echinoderm". Dictionary.com Unabridged (Online). n.d.
- ^ Hall, Danielle (3 February 2022). "Echinoderms | Smithsonian Ocean". ocean.si.edu. Retrieved 31 March 2023.