Coelenterata: Difference between revisions
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{{Taxobox | color = pink |
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'''Coelenterata''', '''coelenterates''', or '''coelentera''' are primitive animals, whose body ultimately is a cavity with an opening. They have very simple tissue organisation, with only two layers of cells, external and internal. |
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| name = Coelenterata |
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| image= Comb_jellies-mba.jpg |
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| image_caption = [[Ctenophora|Comb jellies]] (''Beroe'' spp.) |
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| regnum = [[Animal]]ia |
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| unranked_phylum = ''Coelenterata'' |
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| subdivision_ranks = [[Phylym (biology)|Phyla]] |
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| subdivision = |
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[[Ctenophora]]<br> |
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[[Cnidaria]]<br> |
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}} |
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'''Coelenterata''' is an obsolete yet common term encompassing two animal phyla, the [[Ctenophora]] (comb jellies) and the [[Cnidaria]] ([[coral]] animals, true jellies, sea anemones, sea pens, and their allies). The taxon name comes from the Greek "koilos" ("hollow"), referring to the hollow body cavity common to these two phyla. They have very simple tissue organisation, with only two layers of cells, external and internal. |
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== Controversies in terminology == |
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== History of classification == |
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Use of this term to describe [[Cnidaria|Phylum Cnidaria]] is very common, but considered inaccurate by some biologists. |
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The term ''coelenterate'' is no longer recognized as scientifically valid, as the Cnidaria and Ctenophora have placed at equal rank under the [[Metazoa]] with the other phyla of animals.{{ref|1}} A single term encompassing these two phyla but leaving out all others of equal rank would be considered [[polyphyletic]]. Nonetheless, the term ''coelenterate'' is still used in informal settings to refer to the Cnidaria and Ctenophora. |
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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 [[Porifera|sponges]], [[Trichoplax]], and the still poorly-understood [[Mesozoa]].) Neither grouping is accepted univerally{{ref|2}}; however, both are commonly encountered in taxonomic literature. |
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The term '''Coelenterata''' often refers to a [[polyphylia|polyphyletic]] group of animals, and was generally considered to include [[cnidaria]] and [[Comb jelly|comb jellies]].{{ref|britannica}} But many modern classifications state that [[cnidaria]] and [[comb jelly|comb jellies]] both belong to [[Radiata]] group. |
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Thus, there is a controversy over the usage of the term "coelentarata". It may mean either [[cnidaria]] or [[radiata]]. Because of this, the term is avoided in modern literature. |
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== Classification == |
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There is a controversy on classification of Radiata as to the presence and status of Coelenterata. One of the points of view on classification of Coelenterata was:{{fact}} |
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*Superdomain: [[Biota]] ([[Vitae]]) |
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**Domain: [[Eukarya|Eucytota]] ([[Eukarya]]) |
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***Subdomain: [[Opistokonta]] |
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****Kingdom: [[Metazoa]] ([[Animalia]]) |
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******Branch: [[Radiata]] |
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*******'''Infrakingdom: Coelenterata''' |
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********'''Phylum: [[Vendobionta]] †''' |
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********'''Phylum: [[Myxozoa]]''' |
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********'''Phylum: [[Cnidaria]]''' |
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********'''Phylum: [[Ctenophora]]''' |
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Many modern classifications do not include Coelenterata in their structure,{{ref|1}} considering it a polyphyletic group. |
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== References == |
== References == |
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Revision as of 08:21, 27 August 2006
| Coelenterata | |
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| Comb jellies (Beroe spp.) | |
| Scientific classification | |
| Kingdom: | |
| Subkingdom: | |
| (unranked): | Coelenterata
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| Phyla | |
Coelenterata is an obsolete yet common term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies). The taxon name comes from the Greek "koilos" ("hollow"), referring to the hollow body cavity common to these two phyla. They have very simple tissue organisation, with only two layers of cells, external and internal.
History of classification
The term coelenterate is no longer recognized as scientifically valid, as the Cnidaria and Ctenophora have placed at equal rank under the Metazoa with the other phyla of animals.[1] A single term encompassing these two phyla but leaving out all others of equal rank would be considered polyphyletic. 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 univerally[2]; however, both are commonly encountered in taxonomic literature.
References
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