Coelenterata

Coelenterata
Comb jellies (Beroe spp.)
Scientific classification
Kingdom:	Animalia
Subkingdom:	Eumetazoa
(unranked):	Coelenterata
Phyla
Ctenophora Cnidaria

Coelenterata is an obsolete term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (corals, jellies and hydras animals, true jellies, sea anemones, sea pens, and their allies). The name comes from the Greek "koilos" ("full bellied"), referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, external and internal and radial symmetry. Some of the examples are corals, sea anemone which are colonial and hydra, jelly fish which are solitary.

Characteristics

All coelenterates are aquatic, mostly marine. The body has a single opening hypostome surrounded by sensory tentacles. These animals generally reproduce asexually by budding.

History of classification

The term coelenterate( pronounced as "silentarete") is no longer recognized as scientifically valid, as the Cnidaria and Ctenophora are placed at equal rank under the Metazoa with the other phyla of animals. Cnidaria means "to sting" A single term encompassing these two phyla but leaving out all others of equal rank would be considered paraphyletic. Nonetheless, the term coelenterate is still used in informal settings to refer to the Cnidaria and Ctenophora.

Complicating the issue is the 1997 work of Lynn Margulis (revising an earlier model by Thomas Cavalier-Smith) that placed the Cnidaria and Ctenophora alone under the Radiata branch of the Eumetazoa subregnum. (The latter refers to all the animals except the sponges, Trichoplax, and the still poorly-understood Mesozoa.) Neither grouping is accepted universally; however, both are commonly encountered in taxonomic literature.