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From Wikipedia, the free encyclopedia

Fossil range: Ediacaran - Recent
A moon jellyfish, Aurelia aurita
Scientific classification
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Radiata
Linnaeus, 1758

The Radiata are the radially symmetric animals of the Eumetazoa subregnum. The term Radiata has had various meanings in the history of classification. It has been applied to the echinoderms, although the echinoderms are members of the Bilateria, because they exhibit bilateral symmetry in their developing stages.

Thomas Cavalier-Smith in 1983 defined a subkingdom called Radiata consisting of the phyla Porifera, Myxozoa, Placozoa, Cnidaria and Ctenophora in Radiata, that is, all the animals that are not in Bilateria.

The Five Kingdom classification of Lynn Margulis and K. V. Schwartz keeps only Cnidaria and Ctenophora in Radiata. Cladistic classifications do not recognize Radiata as a clade. The radiata, in this sense, are diploblastic, meaning they have 2 primary germ layers: endoderm and ectoderm. (Cavalier-Smith's use of the term Radiata includes animals with a single germ layer such as sponges.)

Although radial symmetry is usually given as a defining characteristic of radiates, a few members of the class Anthozoa, which are now considered as the most basal and oldest group of cnidarians, are actually bilateral symmetric. Nematostella vectensis is one such example. Newer research strongly indicates that bilateral symmetry evolved before the split between Cnidaria and Bilateria, and that the radially symmetrical cnidarians have secondarily evolved radial symmetry, meaning the bilaterism in species like N. vectensis have a primary origin [1]. Also the free-swimming planula larvae of cnidarians exhibit bilateral symmetry. Ctenophores show biradial symmetry.



1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

RADIATA, a term introduced by Cuvier in 1812 to denote the lowest of his four great animal groups or "embranchements." He defined them as possessing radial instead of bilateral symmetry, and as apparently destitute of nervous system and sense organs, as having the circulatory system rudimentary or absent, and the respiratory organs on or coextensive with the surface of the body; he included under this title and definition five classes, - Echinodermata, Acalepha, Entozoa, Polypi and Infusoria. Lamarck (Hist. nat. d. Anim. s. Vertebres) also used the term, as when he spoke of the Medusae as radiata medusaria et anomala; but he preferred the term Radiaria, under which he included Echinodermata and Medusae. Cuvier's term in its wide extension, however, passed into general use; but, as the anatomy of the different forms became more fully known, the difficulty of including them under the common designation made itself increasingly obvious. Milne-Edwards removed the Polyzoa; the group was soon further thinned by the exclusion of the Protozoa on the one hand and the Entozoa on the other; while in 1848 Leuckart and Frey clearly distinguished the Coelenterata from the Echinodermata as a separate sub-kingdom, thus condemning the usage by which the term still continued to be applied to these two groups at least. In 18J5, however, Owen included under Lamarck's term Radiaria the Echinodermata, Anthozoa, Acalepha and Hydrozoa, while Agassiz also clung to the term Radiata as including Echinodermata, Acalepha and Polypi, regarding their separation into Coelenterata and Echinodermata as "an exaggeration of their anatomical differences" (Essay on Classification, London, 1859). These attempts, however, to perpetuate the usage were finally discredited by Huxley's important Lectures on Comparative Anatomy (1864), in which the term was finally abolished, and the "radiate mob" finally distributed among the Echinodermata, Polyzoa, Vermes (Platyhelminthes), Coelenterata and Protozoa.

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Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also radiata




Latin radio to beam, to shine

Proper noun

Wikipedia has an article on:



  1. a taxonomic superphylum, within subkingdom Eumetazoa - radially symmetric animals

Related terms

Wikispecies has information on:



Up to date as of January 23, 2010

From Wikispecies


Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Superphylum: Radiata
Phyla: Cnidaria - Ctenophora - †Trilobozoa


  • Gordon, D.P. (ed.) 2009: New Zealand inventory of biodiversity. Volume 1. Kingdom Animalia. Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch, New Zealand.

Vernacular names

Česky: Láčkovci
Deutsch: Hohltiere
Ελληνικά: Ακτινωτά
Español: Radiados
Français: Radiaires, Radiés
한국어: 방사대칭동물류
Magyar: Sugaras szimmetriájú állatok
Македонски: Животни со радијална симетрија
日本語: 放射相称動物上門
Polski: Promieniste
Suomi: Radiaalisymmetriset eläimet
Svenska: Radialsymmetriska djur
Türkçe: Işınsal simetrili hayvanlar
Wikimedia Commons For more multimedia, look at Radiata on Wikimedia Commons.


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