Eumetazoa

Eumetazoa Temporal range: Ediacaran - Present (Possible Cryogenian and Tonian origin) , 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? (If sponges occupy the basalmost position of the metazoan tree) †Chancelloriida[1] ParaHoxozoa Placozoa? Planulozoa Cnidaria Bilateria †Proarticulata? Xenacoelomorpha Nephrozoa †Trilobozoa[2]
Synonyms
Enterozoa Lankester, 1877, em. Beklemishev[3][4] Epitheliozoa Ax, 1996 Histozoa Ulrich, 1950[5][6]

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 Porifera (sponges).^{[7][8][9][10][11]} 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.^[12] 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 is the sister group to Agnotozoa, forming Monoblastozoa/Simplecita. Several other extinct or obscure life forms, such as Iotuba and Thectardis, appear to have emerged in the group.^[13] 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.^[14]

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.^[15] 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 the subkingdom Eumetazoa.