Eumetazoa
Basal animal clade as a sister group of the Porifera / From Wikipedia, the free encyclopedia
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Eumetazoa (from Ancient Greek εὖ (eû) 'well', μετά (metá) 'after', and ζῷον (zôion) 'animal'), also known as diploblasts, Epitheliozoa, or Histozoa, are a proposed basal animal clade as a sister group of the Porifera (sponges).[5][6][7][8][9] The basal eumetazoan clades are the Ctenophora and the ParaHoxozoa. Placozoa is now also seen as a eumetazoan in the ParaHoxozoa.
Eumetazoans | |
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Diversity of eumetazoans | |
Scientific classification ![]() | |
Domain: | Eukaryota |
(unranked): | Amorphea |
Clade: | Obazoa |
(unranked): | Opisthokonta |
(unranked): | Holozoa |
(unranked): | Filozoa |
Kingdom: | Animalia |
Subkingdom: | Eumetazoa Buetschli, 1910 |
Phyla | |
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Synonyms | |
Several other extinct or obscure life forms, such as Iotuba and Thectardis, appear to have emerged in the group.[10] Characteristics of eumetazoans include true tissues organized into germ layers, the presence of neurons and muscles, and an embryo that goes through a gastrula stage.
Some phylogenists once speculated the sponges and eumetazoans evolved separately from different single-celled organisms, which would have meant 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, now unanimously support a common origin.[11]
Traditionally, 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.[12] 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.