|
|
|
|
|
EcdysozoaThe Ecdysozoa are a large group of protostomian animals, erected by Aguinaldo et al. in 1997 primarily based on 18s rRNA data. They are sometimes ranked as a superphylum. The name comes from the Greek words ecdysis (molting) and zoon (animal) after a characteristic common to the group. Phyla considered Ecdysozoa are: The non-pararthropoda have sometimes been considered a monophyletic group, occasionally called the Cycloneuralia, but they are more likely paraphyletic. The rotifers and Chaetognatha have also been considered possible members, but this is no longer supported. Besides the rRNA (and other nucleic acid) sequencing data, some morphologic characteristics are common to the Ecdysozoa: - cuticle built of organic material
- molting (ecdysis), initiated by hormones
- trilayered cuticle
Further characters include: Supertaxa corresponding roughly to the Ecdysozoa were previously proposed by Perrier in 1897 and Seurat in 1920 (discussed in Chitwood & Chitwood 1974) on the basis of morphology alone. The Ecdysozoa concept resolves some morphologic problems like the occurrence of a triradiate muscular sucking pharynx in both tardigrades (whose bauplan reminds one strongly of arthropods) and roundworms. It is contradictory to the more traditional Articulata concept, where the Panarthropoda are combined to one taxon with the annelids. The annelids do not belong to Ecdysozoa but instead to the Trochozoa. References - Aguinaldo, A. M. A., J. M. Turbeville, L. S. Linford, M. C. Rivera, J. R. Garey, R. A. Raff, & J. A. Lake, 1997. Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387: 489-493.
- Wagele, J. W., T. Erikson, P. Lockhart, & B. Misof, 1999. The Ecdysozoa: Artifact or monophylum? J. Zoo. Syst. Evol. Research 37: 211-223.
External Links - http://www.ucmp.berkeley.edu/phyla/ecdysozoa.html
- http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html
- http://nema.cap.ed.ac.uk/tardigrades/Tardigrades_and_Ecdysozoa.html
- http://chuma.cas.usf.edu/~garey/articulata.html
- http://chuma.cas.usf.edu/~garey/essential.html
|
 |
|
| Copyright 2005-2009 OnPedia.com. All Rights Reserved |
|
|