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Eumetazoa (Greek: εὖ [eu], well + μετά [metá], after + ζῷον [zóon], animal) is a clade comprising all major animal groups except sponges, placozoa, and several other obscure or extinct life forms, such as Dickinsonia. Characteristics of eumetazoans include true tissues organized into germ layers, the presence of neurons, and an embryo that goes through a gastrula stage. The clade is usually held to contain at least Ctenophora, Cnidaria, and Bilateria. Whether mesozoans and placozoans belong is in dispute. Ctenophora now appear basal metazoa.^[1]

Some phylogenists have speculated the sponges and eumetazoans evolved separately from single-celled organisms, which would mean that the animal kingdom does not form a clade (a complete grouping of all organisms descended from a common ancestor). However, genetic studies and some morphological characteristics, like the common presence of choanocytes, support a common origin.^[2]

Eumetazoans are a major group of animals in the Five Kingdoms classification of Lynn Margulis and K. V. Schwartz, comprising the Radiata and Bilateria — all animals except the sponges, placozoans and mesozoans.^[3] When treated as a formal taxon Eumetazoa is typically ranked as a subkingdom. The name Metazoa has also been used to refer to this group, but more often refers to the Animalia as a whole. Many classification schemes do not include a subkingdom Eumetazoa.

Taxonomy

Over the last decade^[specify], the work of developmental biologists and molecular phylogeneticists spawned new ideas about bilaterian relationships resulting in a paradigm shift.

The current widely accepted hypothesis, based on molecular data (mostly 18S rRNA sequences), divides Bilateria into the following four superphylums: Deuterostomia, Ecdysozoa, Lophotrochozoa, and Platyzoa (sometimes included in Lophotrochozoa). The last three groups are also collectively known as Protostomia.^[4]

However, many skeptics emphasize the pitfalls and inconsistencies associated with the new data. Claus Nielsen, a professor of evolutionary invertebrate embryology at the Zoological Museum University of Copenhagen champions one of the most prominent alternative views based on morphological evidence. In his 2001 book Animal Evolution: Interrelationships of the Living Phyla, he maintains the traditional divisions of Protostomia and Deuterostomia.

Evolutionary origins

It has been suggested that one type of molecular clock and one approach to interpretation of the fossil record both place the evolutionary origins of eumetazoa in the Ediacaran.^[5] However, the earliest eumetazoans may not have left a clear impact on the fossil record and other interpretations of molecular clocks suggest the possibility of an earlier origin.^[6] The discoverers of Vernanimalcula describe it as the fossil of a bilateral triploblastic animal that appeared at the end of the Marinoan glaciation prior to the Ediacaran Period, implying an even earlier origin for eumetazoans.^[7]

References

^ Ryan, J. F.; Pang, K.; Schnitzler, C. E.; Nguyen, A.-D.; Moreland, R. T.; Simmons, D. K.; Koch, B. J.; Francis, W. R.; Havlak, P.; Smith, S. A.; Putnam, N. H.; Haddock, S. H. D.; Dunn, C. W.; Wolfsberg, T. G.; Mullikin, J. C.; Martindale, M. Q.; Baxevanis, A. D. (13 December 2013). "The Genome of the Ctenophore Mnemiopsis leidyi and its Implications for Cell Type Evolution". Science 342 (6164, number 6164): 1242592. doi:10.1126/science.1242592. PMC 3920664. PMID 24337300.
^ Philippe H, Derelle R, Lopez P, et al. (April 2009). "Phylogenomics revives traditional views on deep animal relationships". Curr. Biol. 19 (8): 706–12. doi:10.1016/j.cub.2009.02.052. PMID 19345102.
^ Systema Naturae 2000 Taxon: Subkingdom Eumetazoa — retrieved February 2, 2006
^ Protostomia
^ Peterson KJ, Butterfield NJ (July 2005). "Origin of the Eumetazoa: testing ecological predictions of molecular clocks against the Proterozoic fossil record". Proc. Natl. Acad. Sci. U.S.A. 102 (27): 9547–52. Bibcode:2005PNAS..102.9547P. doi:10.1073/pnas.0503660102. PMC 1172262. PMID 15983372.
^ Blair, J. E.; Hedges, S. B. (2005). "Molecular clocks do not support the Cambrian explosion". Molecular Biology and Evolution 22 (3): 387–390. doi:10.1093/molbev/msi039. PMID 15537810.
^ Chen, J.-Y.; Bottjer, D.J.; Oliveri, P.; Dornbos, S.Q.; Gao, F.; Ruffins, S.; Chi, H.; Li, C.-W.; Davidson, E.H. et al. (2005). "Small bilaterian fossils from 40 to 55 million years before the Cambrian". Science 305 (5681): 218–222. Bibcode:2004Sci...305..218C. doi:10.1126/science.1099213. PMID 15178752.

External links

Bilateria. Tree of Life web project, US National Science Foundation. 2002. 6 January 2006.
Invertebrates and the Origin of Animal Diversity
Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.
TRICHOPLAX ADHAERENS (PLACOZOA TYPE) St. Petersburg. 2005
Metazoa: the Animals
Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla, 2nd edition, 563 pp. Oxford Univ. Press, Oxford. ISBN 0-19-850681-3
Borchiellini, C. Manuel, M., Alivon, E., Boury-Esnault N., Vacelet, J., Le-Parco, Y. 2001. Journal of Evolutionary Biology 14 (1): 171–179.
Peterson, Kevin J., McPeek, Mark A., & Evans, David A.D. 2005. Tempo & mode of early animal evolution: inferences from rocks, Hox, & molecular clocks. Paleobiology 31(2, Supplement): 36–55.

Wikispecies has information related to: Eumetazoa

English Journal

Evolution of the thioester-containing proteins (TEPs) of the arthropoda, revealed by molecular cloning of TEP genes from a spider, Hasarius adansoni.

Sekiguchi R, Fujito NT, Nonaka M.SourceDepartment of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
Developmental and comparative immunology.Dev Comp Immunol.2011 May 31. [Epub ahead of print]
The thioester-containing protein (TEP) family of genes, found in most Eumetazoan genomes, is classified into two subfamilies: the alpha-2-macroglobulin (A2M) subfamily and the C3 subfamily. Many A2M subfamily members, including insect TEP (iTEP), have been reported from the Arthropoda, whereas the C
PMID 21663759

Interkinetic nuclear migration is a broadly conserved feature of cell division in pseudostratified epithelia.

Meyer EJ, Ikmi A, Gibson MC.SourceStowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
Current biology : CB.Curr Biol.2011 Mar 22;21(6):485-91. Epub 2011 Mar 3.
Animal development requires tight integration between the processes of proliferative growth and epithelial morphogenesis, both of which play out at the level of individual cells. In this respect, not only must polarized epithelial cells assume complex morphologies, these distinct forms must be radic
PMID 21376598

Japanese Journal

全球凍結と生物進化

田近英一
地學雜誌 116(1), 79-94, 2007-02-25
… It would be much more difficult for eumetazoa to survive such severe conditions if they appeared before the Neoproterozoic glaciations as suggested by molecular clock studies. … The appearance of eumetazoa after the last global glaciation (Marinoan glaciation), as suggested by the paleontological record, however, avoids this problem. …
NAID 10025675779

Related Pictures

★リンクテーブル★

リンク元	「真正後生動物」「真正後生動物亜門」

「真正後生動物」

Eumetazoa; Temporal range: Ediacaran–Recent PreЄ Є O S D C P T J K Pg N
	A lancelet
Scientific classification
Domain:	Eukaryota
(unranked):	Opisthokonta
Kingdom:	Animalia
Subkingdom:	Eumetazoa; Buetschli, 1910
Phyla
	Radiata (unranked) Ctenophora; Cnidaria; Bilateria (unranked) Orthonectida; Rhombozoa; Acoelomorpha; Chaetognatha; Superphylum Deuterostomia Chordata; Hemichordata; Echinodermata; Xenoturbellida; Vetulicolia †; ; Protostomia (unranked) Superphylum Ecdysozoa Kinorhyncha; Loricifera; Priapulida; Nematoda; Nematomorpha; Lobopodia†; Onychophora; Tardigrada; Arthropoda; ; Superphylum Platyzoa Platyhelminthes; Gastrotricha; Rotifera; Acanthocephala; Gnathostomulida; Micrognathozoa; Cycliophora; ; Superphylum Lophotrochozoa Sipuncula; Hyolitha†; Nemertea; Phoronida; Bryozoa; Entoprocta; Brachiopoda; Mollusca; Annelida; Echiura; ; ;

　　[★]

ラ: Eumetazoa
関: 真正後生動物亜門

「真正後生動物亜門」

　　[★]

ラ: Eumetazoa
関: 真正後生動物

[Ryan2013-1] Ryan, J. F.; Pang, K.; Schnitzler, C. E.; Nguyen, A.-D.; Moreland, R. T.; Simmons, D. K.; Koch, B. J.; Francis, W. R.; Havlak, P.; Smith, S. A.; Putnam, N. H.; Haddock, S. H. D.; Dunn, C. W.; Wolfsberg, T. G.; Mullikin, J. C.; Martindale, M. Q.; Baxevanis, A. D. (13 December 2013). "The Genome of the Ctenophore Mnemiopsis leidyi and its Implications for Cell Type Evolution". Science 342 (6164, number 6164): 1242592. doi:10.1126/science.1242592. PMC 3920664. PMID 24337300.

[2] Philippe H, Derelle R, Lopez P, et al. (April 2009). "Phylogenomics revives traditional views on deep animal relationships". Curr. Biol. 19 (8): 706–12. doi:10.1016/j.cub.2009.02.052. PMID 19345102.

[3] Systema Naturae 2000 Taxon: Subkingdom Eumetazoa — retrieved February 2, 2006

[4] Protostomia

[5] Peterson KJ, Butterfield NJ (July 2005). "Origin of the Eumetazoa: testing ecological predictions of molecular clocks against the Proterozoic fossil record". Proc. Natl. Acad. Sci. U.S.A. 102 (27): 9547–52. Bibcode:2005PNAS..102.9547P. doi:10.1073/pnas.0503660102. PMC 1172262. PMID 15983372.

[6] Blair, J. E.; Hedges, S. B. (2005). "Molecular clocks do not support the Cambrian explosion". Molecular Biology and Evolution 22 (3): 387–390. doi:10.1093/molbev/msi039. PMID 15537810.

[7] Chen, J.-Y.; Bottjer, D.J.; Oliveri, P.; Dornbos, S.Q.; Gao, F.; Ruffins, S.; Chi, H.; Li, C.-W.; Davidson, E.H. et al. (2005). "Small bilaterian fossils from 40 to 55 million years before the Cambrian". Science 305 (5681): 218–222. Bibcode:2004Sci...305..218C. doi:10.1126/science.1099213. PMID 15178752.

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Eumetazoa