Eumetazoa

Eumetazoa Temporal range: Ediacaran - Present 600–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa Buetschli, 1910
Subdivisions
Ctenophora †Chancelloriida[1] ParaHoxozoa Placozoa? Planulozoa Cnidaria Bilateria †Proarticulata? Xenacoelomorpha Nephrozoa Ctenophora[2] (sometimes included) †Trilobozoa?[3]
Synonyms
Enterozoa Lankester, 1877, em. Beklemishev[4][5] Epitheliozoa Ax, 1996 Histozoa Ulrich, 1950[6][7]

Eumetazoa (from Ancient Greek εὖ (eû) 'well' μετά (metá) 'after' and ζῷον (zôion) 'animal'), also known as Epitheliozoa or Histozoa, is a proposed basal animal subkingdom as a sister group of Porifera (sponges).^{[8][9][10][11][12]} The basal eumetazoan clades are the Ctenophora and the ParaHoxozoa. Placozoa is now also seen as a eumetazoan in the ParaHoxozoa. The competing hypothesis is the Myriazoa clade.^[13] The subkingdom Parazoa and Agnotozoa are the other taxa, and agnotozoa may be fake or even nonexistent at studies. Parazoa or Agnotozoa are a main sister group to eumetazoans, forming clade Blastozoa/Diploblastozoa. Alternatively, Parazoa was considered as a sister group to Agnotozoa(now considered polyphyletic). Several other extinct or obscure life forms, such as Iotuba and Thectardis, appear to have emerged in the group.^[14] 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.^[15]

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.^[16].