{{Short description|Basal animal clade as a sister group of the Porifera}} {{Automatic taxobox | fossil_range = Ediacaran - Present {{fossil range|600|0|earliest= 635}} | image = Epitheliozoa collage.png | taxon = Eumetazoa | authority = Buetschli, 1910 | subdivision_ranks = Subdivisions | subdivision =*{{extinct}}Petalonamae **{{extinct}}Arboreomorpha?<ref>{{Cite journal|last1=Dunn|first1=Frances S.|last2=Liu|first2=Alexander G.|last3=Gehling|first3=James G.|date=2019-05-17|title=Anatomical and ontogenetic reassessment of the Ediacaran frond Arborea arborea and its placement within total group Eumetazoa|journal=Palaeontology|volume=62|issue=5|pages=851–865|doi=10.1111/pala.12431|bibcode=2019Palgy..62..851D |issn=0031-0239|doi-access=free|hdl=1983/5677888d-1cd1-4e92-8aa8-57940f30626a|hdl-access=free}}</ref> **{{extinct}}Rangeomorpha?<ref>{{Cite journal |last1=Dunn |first1=Frances S. |last2=Liu |first2=Alexander G. |last3=Grazhdankin |first3=Dmitriy V. |last4=Vixseboxse |first4=Philip |last5=Flannery-Sutherland |first5=Joseph |last6=Green |first6=Emily |last7=Harris |first7=Simon |last8=Wilby |first8=Philip R. |last9=Donoghue |first9=Philip C. J. |date=2021-07-23 |title=The developmental biology of Charnia and the eumetazoan affinity of the Ediacaran rangeomorphs |journal=Science Advances |language=en |volume=7 |issue=30 |article-number=eabe0291 |doi=10.1126/sciadv.abe0291 |issn=2375-2548 |pmc=8302126 |pmid=34301594 |bibcode=2021SciA....7..291D }}</ref> *Ctenophora *{{extinct}}Chancelloriida<ref>{{cite journal|doi=10.1080/08912963.2023.2212382 |title=Flourishing chancelloriids from the Cambrian Kaili Biota of South China |date=2024 |last1=Peng |first1=Tingzu |last2=Yang |first2=Yuning |last3=Yun |first3=Hao |last4=Yang |first4=Xinglian |last5=Zhang |first5=Qianqian |last6=He |first6=Min |last7=Chi |first7=Xiangri |last8=Liu |first8=Jing |last9=Liu |first9=Xi |journal=Historical Biology |volume=36 |issue=7 |pages=1302–1320 |bibcode=2024HBio...36.1302P |doi-access=free }}</ref> * ParaHoxozoa ** Placozoa? ** Planulozoa *** Cnidaria *** Bilateria ****{{extinct}}Proarticulata? ****Xenacoelomorpha ****Nephrozoa *{{extinct}}Trilobozoa?<ref name="Fedonkin1990">Fedonkin, M. A. (1990). Systematic description of Vendian Metazoa. In: Sokolov, B. S. & Iwanowski, A. B. (eds), *The Vendian System: Historical–Geological and Paleontological Foundation*, Vol. 1. Springer, pp. 71–120. Fedonkin describes trilobozoans as coelenterate-like organisms, implying eumetazoan affinities.</ref> | synonyms = *Enterozoa <small>Lankester, 1877, em. Beklemishev</small><ref>Lankester, Ray (1877). "Notes on the Embryology and classification of the Animal kingdom: comprising a revision of speculations relative to the origin and significance of the germ-layers". ''Quarterly Journal of Microscopical Science'' (N.S.), No. 68: 399–454.</ref><ref>Beklemishev, V. L. ''The basis of the comparative anatomy of the invertebrates'' [''Основы сравнительной анатомии беспозвоночных'']. 1st ed., 1944; 2nd ed., 1950; 3rd ed. (2 vols.), 1964. English translation, 1969, [https://archive.org/details/principlesofcomp0002bekl]. Akademia Nauk, Moscow, Leningrad.</ref>
* Epitheliozoa <small>Ax, 1996</small> *Histozoa <small>Ulrich, 1950</small><ref>{{Cite book|url=https://books.google.com/books?id=T8fyCAAAQBAJ&q=epitheliozoa&pg=PA77|title=Multicellular Animals: A new Approach to the Phylogenetic Order in Nature|last=Ax|first=Peter|date=2012-12-06|publisher=Springer Science & Business Media|isbn=9783642801143|language=en}}</ref><ref>{{cite book |last=Ulrich |first=W. |year=1950 |contribution=Begriff und Einteilung der Protozoen |editor-last=Grüneberg |editor-first=H. |title=Moderne Biologie. Festschrift zum 60. Geburtstag von Hans Nachtsheim |language=de |publisher=Peters |location=Berlin |pages=241–250}}</ref> }}
'''Eumetazoa''' ({{etymology|grc|''{{wikt-lang|grc|εὖ}}'' ({{grc-transl|εὖ}})|well||''{{wikt-lang|grc|μετά}}'' ({{grc-transl|μετά}})|after||''{{wikt-lang|grc|ζῷον}}'' ({{grc-transl|ζῷον}})|animal}}), also known as '''Epitheliozoa''' or '''Histozoa''', is a proposed basal animal subkingdom as a sister group of Porifera (sponges).<ref>{{Cite journal|last1=Feuda|first1=Roberto|last2=Dohrmann|first2=Martin|last3=Pett|first3=Walker|last4=Philippe|first4=Hervé|last5=Rota-Stabelli|first5=Omar|last6=Lartillot|first6=Nicolas|last7=Wörheide|first7=Gert|last8=Pisani|first8=Davide|title=Improved Modeling of Compositional Heterogeneity Supports Sponges as Sister to All Other Animals|journal=Current Biology|volume=27|issue=24|pages=3864–3870.e4|language=en|doi=10.1016/j.cub.2017.11.008|pmid=29199080|year=2017|doi-access=free|bibcode=2017CBio...27E3864F |hdl=10449/43929|hdl-access=free}}</ref><ref>{{Cite journal|last1=Pisani|first1=Davide|last2=Pett|first2=Walker|last3=Dohrmann|first3=Martin|last4=Feuda|first4=Roberto|last5=Rota-Stabelli|first5=Omar|last6=Philippe|first6=Hervé|last7=Lartillot|first7=Nicolas|last8=Wörheide|first8=Gert|date=15 December 2015|title=Genomic data do not support comb jellies as the sister group to all other animals|journal=Proceedings of the National Academy of Sciences |volume=112|issue=50 |pages=15402–15407 |bibcode=2015PNAS..11215402P|doi=10.1073/pnas.1518127112 |pmc=4687580|pmid=26621703|doi-access=free}}</ref><ref name=":0">{{Cite journal|last1=Simion|first1=Paul|last2=Philippe|first2=Hervé|last3=Baurain|first3=Denis|last4=Jager|first4=Muriel|last5=Richter|first5=Daniel J.|last6=Franco|first6=Arnaud Di|last7=Roure|first7=Béatrice|last8=Satoh|first8=Nori|last9=Quéinnec|first9=Éric|date=3 April 2017|title=A Large and Consistent Phylogenomic Dataset Supports Sponges as the Sister Group to All Other Animals|journal=Current Biology |volume=27|issue=7|pages=958–967 |doi=10.1016/j.cub.2017.02.031 |pmid=28318975|url=https://hal.archives-ouvertes.fr/hal-01681528/file/Simion_etal2017_CurrBiol_proofs.pdf|s2cid=4560353|doi-access=free|bibcode=2017CBio...27..958S }}</ref><ref>{{Cite journal|last=Giribet|first=Gonzalo|date=1 October 2016|title=Genomics and the animal tree of life: conflicts and future prospects|journal=Zoologica Scripta |volume=45|pages=14–21|doi=10.1111/zsc.12215|doi-access=free}}</ref><ref>{{Cite journal|last1=Laumer|first1=Christopher E|last2=Gruber-Vodicka|first2=Harald|last3=Hadfield|first3=Michael G|last4=Pearse|first4=Vicki B|last5=Riesgo|first5=Ana|last6=Marioni|first6=John C|last7=Giribet|first7=Gonzalo|date=2018-10-30|title=Support for a clade of Placozoa and Cnidaria in genes with minimal compositional bias|journal=eLife|language=en|volume=7|article-number=e36278 |doi=10.7554/elife.36278|pmid=30373720|pmc=6277202|issn=2050-084X |doi-access=free }}</ref> The basal eumetazoan clades are the Ctenophora and the ParaHoxozoa. Placozoa is now also seen as an eumetazoan clade in the ParaHoxozoa, based on genetic data. The subkingdom Parazoa comprises the sister taxa, which includes primarily Porifera. The competing hypothesis is the Myriazoa clade, which states Ctenophora diverged earlier than Porifera, who instead would make up a clade with ParaHoxozoa, implying either sponges lost complexity or Ctenophores developed complexity independently, and maybe even a mix of both processes<ref name=":1">{{Cite journal |last1=Schultz |first1=Darrin T. |last2=Haddock |first2=Steven H. D. |last3=Bredeson |first3=Jessen V. |last4=Green |first4=Richard E. |last5=Simakov |first5=Oleg |last6=Rokhsar |first6=Daniel S. |date=June 2023 |title=Ancient gene linkages support ctenophores as sister to other animals |journal=Nature |language=en |volume=618 |issue=7963 |pages=110–117 |doi=10.1038/s41586-023-05936-6 |pmid=37198475 |pmc=10232365 |bibcode=2023Natur.618..110S |issn=1476-4687}}</ref><ref>{{Cite journal |last1=Moroz |first1=Leonid L. |last2=Kocot |first2=Kevin M. |last3=Citarella |first3=Mathew R. |last4=Dosung |first4=Sohn |last5=Norekian |first5=Tigran P. |last6=Povolotskaya |first6=Inna S. |last7=Grigorenko |first7=Anastasia P. |last8=Dailey |first8=Christopher |last9=Berezikov |first9=Eugene |last10=Buckley |first10=Katherine M. |last11=Ptitsyn |first11=Andrey |last12=Reshetov |first12=Denis |last13=Mukherjee |first13=Krishanu |last14=Moroz |first14=Tatiana P. |last15=Bobkova |first15=Yelena |date=June 2014 |title=The ctenophore genome and the evolutionary origins of neural systems |journal=Nature |language=en |volume=510 |issue=7503 |pages=109–114 |doi=10.1038/nature13400 |pmid=24847885 |pmc=4337882 |bibcode=2014Natur.510..109M |issn=1476-4687}}</ref><ref>{{Cite journal |last1=Whelan |first1=Nathan V. |last2=Kocot |first2=Kevin M. |last3=Moroz |first3=Tatiana P. |last4=Mukherjee |first4=Krishanu |last5=Williams |first5=Peter |last6=Paulay |first6=Gustav |last7=Moroz |first7=Leonid L. |last8=Halanych |first8=Kenneth M. |date=November 2017 |title=Ctenophore relationships and their placement as the sister group to all other animals |journal=Nature Ecology & Evolution |volume=1 |issue=11 |pages=1737–1746 |doi=10.1038/s41559-017-0331-3 |issn=2397-334X |pmc=5664179 |pmid=28993654 |bibcode=2017NatEE...1.1737W }}</ref><ref>{{Cite journal |last1=Burkhardt |first1=P. |last2=Colgren |first2=J. |last3=Medhus |first3=A. |last4=Digel |first4=L. |last5=Naumann |first5=B. |last6=Soto-Angel |first6=J. J. |last7=Nordmann |first7=E. L. |last8=Sachkova |first8=M. Y. |last9=Kittelmann |first9=M. |title=Science |url=https://www.science.org/action/cookieAbsent |access-date=2026-05-20 |journal=Science |date=2023 |volume=380 |issue=6642 |pages=293–297 |language=en |doi=10.1126/science.ade5645 |pmc=7617566 |pmid=37079688}}</ref>. As far as May 2026, this question remains unresolved and the dispute may became combative, with some scientists deciding to not participate into the debate<ref>{{Cite journal |last=Callaway |first=Ewen |date=2026-01-27 |title=What were the first animals? The fierce sponge–jelly battle that just won't end |url=https://www.nature.com/articles/d41586-026-00238-z |journal=Nature |language=en |volume=649 |issue=8099 |pages=1096–1098 |doi=10.1038/d41586-026-00238-z |pmid=41593281 |bibcode=2026Natur.649.1096C |issn=1476-4687|url-access=subscription }}</ref>.
Agnothozoa were once considered an intermediary clade between Parazoa and Eumetazoa, being the sister clade to Parazoa which Eumetazoa would late derivate from. The group primarily encompassed the clade Placozoa and the proposed clade Mesozoa who groups Orthonectida, Dicyemida and the dubious Monoblastozoa, but now are largely considered a polyphyletic group of simplified eumetazoans<ref name=":1" /><ref name=":0" /><ref>{{Cite journal |last1=Zverkov |first1=Oleg A. |last2=Mikhailov |first2=Kirill V. |last3=Isaev |first3=Sergey V. |last4=Rusin |first4=Leonid Y. |last5=Popova |first5=Olga V. |last6=Logacheva |first6=Maria D. |last7=Penin |first7=Alexey A. |last8=Moroz |first8=Leonid L. |last9=Panchin |first9=Yuri V. |last10=Lyubetsky |first10=Vassily A. |last11=Aleoshin |first11=Vladimir V. |date=2019-05-24 |title=Dicyemida and Orthonectida: Two Stories of Body Plan Simplification |journal=Frontiers in Genetics |language=English |volume=10 |article-number=443 |doi=10.3389/fgene.2019.00443 |doi-access=free |pmid=31178892 |pmc=6543705 |issn=1664-8021}}</ref><ref>{{Cite journal |last1=Nikolaeva |first1=Olga V. |last2=Mikhailov |first2=Kirill V. |last3=Muntyan |first3=Maria S. |last4=Zverkov |first4=Oleg A. |last5=Spirin |first5=Sergey A. |last6=Lyubetsky |first6=Vassily A. |last7=Slyusarev |first7=Georgy S. |last8=Aleoshin |first8=Vladimir V. |date=2025-06-21 |title=Rare Evolutionary Events Support the Phylogenetic Placement of Orthonectida Within Annelida |journal=International Journal of Molecular Sciences |volume=26 |issue=13 |pages=5983 |doi=10.3390/ijms26135983 |doi-access=free |issn=1422-0067 |pmc=12249979 |pmid=40649762}}</ref><ref>{{Cite journal |last1=Mendivil Ramos |first1=Olivia |last2=Barker |first2=Daniel |last3=Ferrier |first3=David E. K. |date=2012-10-23 |title=Ghost loci imply Hox and ParaHox existence in the last common ancestor of animals |journal=Current Biology: CB |volume=22 |issue=20 |pages=1951–1956 |doi=10.1016/j.cub.2012.08.023 |issn=1879-0445 |pmid=23022064 |bibcode=2012CBio...22.1951M }}</ref>. Though some archaic fossil groups such as Chancelloriidae and Petalonamae, may, based on weaker morphological evidence, still be considered members of intermediate clades before the crown group Eumetazoa.<ref>{{Cite journal |last1=Hoyal Cuthill |first1=Jennifer F. |last2=Han |first2=Jian |date=November 2018 |editor-last=Álvaro |editor-first=Javier |title=Cambrian petalonamid Stromatoveris phylogenetically links Ediacaran biota to later animals |journal=Palaeontology |language=en |volume=61 |issue=6 |pages=813–823 |doi=10.1111/pala.12393 |issn=0031-0239|doi-access=free |bibcode=2018Palgy..61..813H }}</ref><ref>{{Cite journal |last1=Dunn |first1=F. S. |last2=Liu |first2=A. G. |last3=Grazhdankin |first3=D. V. |last4=Vixseboxse |first4=P. |last5=Flannery-Sutherland |first5=J. |last6=Green |first6=E. |last7=Harris |first7=S. |last8=Wilby |first8=P. R. |author9=Donoghue PCJ |title=Science |url=https://www.science.org/action/cookieAbsent |access-date=2026-04-28 |journal=Science Advances |date=2021 |volume=7 |issue=30 |language=en |doi=10.1126/sciadv.abe0291 |pmc=8302126 |pmid=34301594 |bibcode=2021SciA....7..291D }}</ref><ref>{{Cite journal |last1=Yun |first1=Hao |last2=Zhang |first2=Xingliang |last3=Brock |first3=Glenn A. |last4=Li |first4=Luoyang |last5=Li |first5=Guoxiang |date=June 2021 |title=Biomineralization of the Cambrian chancelloriids |url=https://www.scopus.com/pages/publications/85108142702 |journal=Geology |volume=49 |issue=6 |pages=623–628 |doi=10.1130/G48428.1 |bibcode=2021Geo....49..623Y |issn=0091-7613}}</ref>
Several other extinct or obscure life forms, such as ''Thectardis'', may have emerged in the total group.<ref>{{Cite journal|last1=Martindale|first1=Mark Q.|last2=Kourakis|first2=Matthew J.|title=Hox clusters: Size doesn't matter|journal=Nature|volume=399|issue=6738|pages=730–731 |doi=10.1038/21530 |pmid=10391234|bibcode=1999Natur.399..730M|year=1999|s2cid=43414178 }}</ref> Key characteristics present in most 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.<ref>{{cite journal |first1=Philippe |last1=H. |last2=Derelle |first2=R. |last3=Lopez |first3=P. |title=Phylogenomics revives traditional views on deep animal relationships |journal=Current Biology |volume=19 |issue=8 |pages=706–712 |date=April 2009 |pmid=19345102 |doi=10.1016/j.cub.2009.02.052 |s2cid=15282843 |display-authors=etal|doi-access=free |bibcode=2009CBio...19..706P }}</ref>
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.<ref>[http://sn2000.taxonomy.nl/Taxonomicon/TaxonTree.aspx?id=96007 "Systema Naturae 2000 Taxon: Subkingdom Eumetazoa"]. {{Webarchive|url=https://web.archive.org/web/20090322225846/http://sn2000.taxonomy.nl/Taxonomicon/TaxonTree.aspx?id=96007 |date=2009-03-22 }}. Retrieved February 2, 2006</ref>
==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.<ref>{{cite journal | doi = 10.1073/pnas.0503660102|pmid=15983372 | pmc=1172262 | volume=102 | issue=27 | title=Origin of the Eumetazoa: testing ecological predictions of molecular clocks against the Proterozoic fossil record |date=July 2005 | journal=Proc. Natl. Acad. Sci. U.S.A. | pages=9547–52 |vauthors=Peterson KJ, Butterfield NJ |bibcode = 2005PNAS..102.9547P |doi-access=free }}</ref> 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.<ref>{{cite journal | doi = 10.1093/molbev/msi039 | last1 = Blair | first1 = J. E. | last2 = Hedges | first2 = S. B. | date = March 2005 | title = Molecular clocks do not support the Cambrian explosion | journal = Molecular Biology and Evolution | volume = 22 | issue = 3| pages = 387–390 | pmid = 15537810 | doi-access = free }}</ref> 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.<ref>{{cite journal | doi = 10.1126/science.1099213 | last1 = Chen | first1 = J.-Y. | last2 = Bottjer | first2 = D.J. | last3 = Oliveri | first3 = P. | last4 = Dornbos | first4 = S.Q. | last5 = Gao | first5 = F. | last6 = Ruffins | first6 = S. | last7 = Chi | first7 = H. | last8 = Li | first8 = C.-W. | last9 = Davidson | first9 = E.H. | s2cid = 115443209 | date = 9 July 2004 | title = Small bilaterian fossils from 40 to 55 million years before the Cambrian | journal = Science | volume = 305 | issue = 5681| pages = 218–222 | pmid = 15178752 | bibcode=2004Sci...305..218C|display-authors=etal| doi-access = free }}</ref> Various ediacaran organisms have been tentatively classified as eumetazoans. But so far, very few Ediacaran organisms have been identified as definite eumetazoans like- ''Kimberella'', ''Haootia'' and ''Dickinsonia''. Ediacaran fossils preserve very little details so identifying one as an animal with true tissue is very difficult. Many extinct phyla have been proposed by many researchers that may fall under the clade. These are Proarticulata, Trilobozoa and Petalonamae. The inclusion of these within eumetazoa as well as the position of these within the clade is highly debated and sometimes considered speculative. The proarticulates are considered as stem bilaterians by most authors.<ref>Ivantsov, A. Yu. (2021). "Proarticulates—an extinct phylum of soft-bodied metazoans, or a group of vendobionts par excellence?" ''Symmetry''. '''13'''(2): 160. [https://www.mdpi.com/2073-8994/13/2/160 Full text]. doi:10.3390/sym13020160.</ref> Together the three phyla are grouped as the grade Vendobionta.The petalonamids are often considered as early diverging animals before animals with true tissue organisation started to appear.
==References==<!-- Molecular Phylogenetics and Evolution 46 (2008) 206–214 --> {{Reflist}}
==External links== {{Commons category}} {{Wikispecies|Eumetazoa}} *[http://tolweb.org/tree?group=Bilateria ''Bilateria.''] Tree of Life web project, US National Science Foundation. 2002. 6 January 2006. *[https://web.archive.org/web/20090321190209/http://kentsimmons.uwinnipeg.ca/16cm05/1116/16anim2.htm 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}}. *[https://web.archive.org/web/20130818154046/http://now.ifmo.ru/publications/trichoplax/trichoplax_text.pdf ''TRICHOPLAX ADHAERENS (PLACOZOA TYPE)''] St. Petersburg. 2005 *[https://web.archive.org/web/20080214201116/http://www.palaeos.com/Invertebrates/default.htm#Evolution 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}} <!--10 digit ISBN 0-19-850681-3 or 13 digit ISBN 978-0-19-850681-2 --> * {{cite journal | last1 = Borchiellini | first1 = C. Manuel | last2 = Alivon | first2 = E. | last3 = Boury-Esnault | first3 = N. | last4 = Vacelet | first4 = J. | last5 = Le-Parco | first5 = Y. | year = 2001 | title = Sponge paraphyly and the origin of Metazoa| journal = Journal of Evolutionary Biology | volume = 14 | issue = 1| pages = 171–179 | doi = 10.1046/j.1420-9101.2001.00244.x | pmid = 29280585 | s2cid = 25119754 | doi-access = free }} * {{cite journal | last1 = Peterson | first1 = Kevin J. | last2 = McPeek | first2 = Mark A. | last3 = Evans | first3 = David A.D. | year = 2005 | title = Tempo & mode of early animal evolution: inferences from rocks, Hox, & molecular clocks | journal = Paleobiology | volume = 31 | issue = Supp 2| pages = 36–55 | doi = 10.1666/0094-8373(2005)031[0036:TAMOEA]2.0.CO;2 | s2cid = 30787918 }}
{{Animalia|state=expanded}} {{Taxonbar|from=Q5174}} {{Authority control}}
Category:Animal taxa Category:Subkingdoms Category:Ediacaran first appearances