Radiata

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m (Protected "Radiata" [move=sysop])
(added discussion. Radial symmetry self evident, as is bilateral.)
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'''Radiata''' is a [[taxon]] (usually treated as a [[subkingdom]]) erected to include those [[Animalia|animals]] with [[radial symmetry]], as opposed to [[Bilateria]] with [[bilateral symmetry]]. As such, it has usually included [[Cnidaria]] and [[Ctenophora]], but other authors have included [[Porifera]], [[Myxozoa]], ''[[Trichoplax]]'' and/or [[Echinodermata]]. Currently, the Radiata is regarded as a [[paraphyletic]] or [[polyphyletic]] group.
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'''Radiata''' is a [[taxon]] (usually treated as a [[subkingdom]]) erected to include those [[Animalia|animals]] with radial symmetry, as opposed to [[Bilateria]] with bilateral symmetry. As such, it has usually included [[Cnidaria]] and [[Ctenophora]], but other authors have included [[Porifera]], [[Myxozoa]], ''[[Trichoplax]]'' and/or [[Echinodermata]]. Currently, the Radiata is regarded as a [[paraphyletic]] or [[polyphyletic]] group.
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Except when applied to the diploblastic Cnideria and Ctenoppora, with two germ layers, endoderm and exoderm, the term Radiata has no taxonomic or cladistic meaning.
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Echinodermata simply aren't radiata, in any proper taxonomic sense of the word.  The typical pentaradial symmetry is a secondary development superimposed on a primary bilateral larval symmetry.  Moreover echinocherms are triploblastic deuterostomes. Even anthozoa, polypform Cnideria, have a bilateral aspect their symmetry in the manner in which mesentaries are added, on which side of the mesentaries the retractive muscles are put, and the general shape of the gullet. Tentacle pairs in the Ctenophora even give that group as bilateral aspect.  So what really separates the "Radiata" (s.s.) from higher metazoa is the lack of mesoderm.  i.e they are better described as "Diploblasta" 
'''Credits'''
'''Credits'''
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CKT071221
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CKT071221; JM 110305

Revision as of 01:47, 7 March 2011

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