# Agnotozoa

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> Source: https://en.wikipedia.org/wiki/Agnotozoa
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{{Short description|Animals without organs}}
{{Taxobox
| name = Agnotozoa
| image = Trichoplax mic.jpg
| image_caption = ''[Trichoplax adhaerens](/source/Trichoplax)''.
| regnum = [Animalia](/source/Animalia)
| subregnum = '''Agnotozoa'''
| subregnum_authority = Moore et al., 1952<ref>Moore, Raymond C., Lalicker, Cecil G., & Fischer, Alfred G. 1952. ''Invertebrate Fossils''. McGraw-Hill, New York. Page 17.</ref>
| subdivision_ranks = Phyla
| subdivision = 
* [Placozoa](/source/Placozoa)
* [Mesozoa](/source/Mesozoa)
}}

'''Agnotozoa''' is a rejected [subkingdom](/source/Kingdom_(biology)) of simple animals that is now considered [polyphyletic](/source/Polyphyly). It is one of the three "traditional" animal subkingdoms, along with [Parazoa](/source/Parazoa) and [Eumetazoa](/source/Eumetazoa).<ref>{{Cite book |last=Blackwelder |first=Richard E. |url=https://www.biodiversitylibrary.org/item/29076 |title=Classification of the animal kingdom |date=1963 |publisher=Southern Illinois University Press |location=Carbondale, Ill}}</ref> On some classifications, it is nearly synonymous with [Mesozoa](/source/Mesozoa) which is also considered rejected but with some minority studies still supporting it. Even if Mesozoa were valid their position is unequivocally inside [Bilateria](/source/Bilateria) and not as separate subkingdom.<ref>{{Cite journal |last1=Lu |first1=Tsai-Ming |last2=Kanda |first2=Miyuki |last3=Satoh |first3=Noriyuki |last4=Furuya |first4=Hidetaka |date=2017 |title=The phylogenetic position of dicyemid mesozoans offers insights into spiralian evolution |journal=Zoological Letters |volume=3 |article-number=6 |doi=10.1186/s40851-017-0068-5 |doi-access=free |issn=2056-306X |pmc=5447306 |pmid=28560048}}</ref> Placozoa is now also considered an [Eumetazoan](/source/Eumetazoa) or [Myriazoan](/source/Benthozoa) inside the clade [ParaHoxozoa](/source/ParaHoxozoa). 

Agnotozoa was first used as one of the branches of the subkingdom [Metazoa](/source/Metazoa). It was then considered to contain only one group, Mesozoa.

More recently, some have used the name to refer to a subkingdom of three small phyla of simple animals without organs, [Placozoa](/source/Placozoa), [Orthonectida](/source/Orthonectida), and [Rhombozoa](/source/Rhombozoa). They are known as "simple" though they have differentiated tissue, because that tissue is only organized in simple ways; for example, by being layered. The Orthonectida and Rhombozoa are grouped into the Mesozoa.{{Citation needed|date=January 2023}}

Biologists today generally do not use the taxon Agnotozoa because it is doubted that placozoans are closely related to mesozoans and that orthonectids and rhombozoans are related to each other. Even if the two are related, there is little need for another name in addition to mesozoa.

Agnotozoa represents a novel lineage of microbial eukaryotes that has been identified through environmental sequencing but remains largely uncharacterized due to the challenges of culturing these organisms. Phylogenetic analyses suggest that Agnotozoa may share a common ancestry with certain opisthokont or stramenopile lineages, though their precise evolutionary placement is still debated <ref>{{Cite journal |last1=del Campo |first1=Javier |last2=Guillou |first2=Laure |last3=Hehenberger |first3=Elisabeth |last4=Logares |first4=Ramiro |last5=López-García |first5=Purificación |last6=Massana |first6=Ramon |date=2016-08-01 |title=Ecological and evolutionary significance of novel protist lineages |url=https://www.sciencedirect.com/science/article/abs/pii/S0932473916300025?fr=RR-12&ref=pdf_download&rr=9238db1d9a40e6ec |journal=European Journal of Protistology |series=Current trends in protistology – results from the VII ECOP - ISOP Joint Meeting 2015 |volume=55 |issue=Pt A |pages=4–11 |doi=10.1016/j.ejop.2016.02.002 |pmid=26996654 |issn=0932-4739|hdl=10261/135567 |hdl-access=free |pmc=5242370 }}</ref>

==References==
{{Reflist}}

* {{Wikispecies-inline|Agnotozoa}}

{{Taxonbar|from=Q2366359}}

Category:Obsolete animal taxa
Category:Subkingdoms

{{animal-stub}}

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Adapted from the Wikipedia article [Agnotozoa](https://en.wikipedia.org/wiki/Agnotozoa) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Agnotozoa?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.