clade of all animals except sponges and comb jellies

ParaHoxozoa is a proposed group within taxonomy. It would be a clade, above phylum but below a kingdom.

Temporal range: 605.2–0 Ma Ediacaran-Present
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: ParaHoxozoa
Ryan et al., 2010

It would include the Bilateria, the Placozoa and the Cnidarians.[1][2][3][4][5][6][7]



Parahoxozoa is named after the groups of genes that scientists found in the organisms in it: (sub)classes (HNF, CUT, PROS, ZF, CERS, K50, S50-PRD) and Hox/ParaHox-ANTP. Some scientists said they thought a similar gene, ANTP, the NK gene, and the Cdx Parahox gene were also in sponges in the phylum Porifera, but for now, Parahoxozoa does not have sponges in it.[8][9][10][4]

















Scientists are not sure where to put Placozoa. They think it could be a sister clade to the other Parahoxozoa (the Planulozoa hypothesis) or sister of Cnidaria.

Planula-acoel, triploblasty, and bilaterian similarities


The first bilateral organisms (the first living things that were symmetrical from side to side) were worms which lived on the bottom of bodies of water. This type of worm probably had only one opening in its body instead of both a mouth and an anus, as bilateral organisms do today.[11] A through-gut may already have developed with the ctenophora.[12] The through-gut, the tubelike digestive system with two ends, may have evolved when the organism's one hole closed in the middle. For example, Acoela look like the planula larvae of some cnidarians.[13][14][15]


  1. Feuda, Roberto; Dohrmann, Martin; Pett, Walker; Philippe, Hervé; Rota-Stabelli, Omar; Lartillot, Nicolas; Wörheide, Gert; Pisani, Davide (2017). "Improved Modeling of Compositional Heterogeneity Supports Sponges as Sister to All Other Animals". Current Biology. 6 (24): 3864–3870.e4. doi:10.1016/j.cub.2017.11.008. PMID 29199080.
  2. Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert (15 December 2015). "Genomic data do not support comb jellies as the sister group to all other animals". Proceedings of the National Academy of Sciences. 112 (50): 15402–15407. Bibcode:2015PNAS..11215402P. doi:10.1073/pnas.1518127112. ISSN 0027-8424. PMC 4687580. PMID 26621703.
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  4. 4.0 4.1 Giribet, Gonzalo (1 October 2016). "Genomics and the animal tree of life: conflicts and future prospects". Zoologica Scripta. 45: 14–21. doi:10.1111/zsc.12215. ISSN 1463-6409.
  5. Laumer, Christopher E; Gruber-Vodicka, Harald; Hadfield, Michael G; Pearse, Vicki B; Riesgo, Ana; Marioni, John C; Giribet, Gonzalo (2018-10-30). "Support for a clade of Placozoa and Cnidaria in genes with minimal compositional bias". eLife. 7. doi:10.7554/elife.36278. ISSN 2050-084X. PMC 6277202. PMID 30373720.
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  8. Fortunato, Sofia A. V.; Adamski, Marcin; Ramos, Olivia Mendivil; Leininger, Sven; Liu, Jing; Ferrier, David E. K.; Adamska, Maja (2014-10-30). "Calcisponges have a ParaHox gene and dynamic expression of dispersed NK homeobox genes". Nature. 514 (7524): 620–623. Bibcode:2014Natur.514..620F. doi:10.1038/nature13881. hdl:10023/6597. ISSN 0028-0836. PMID 25355364. S2CID 205241127.
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  11. Cannon, Johanna Taylor; Vellutini, Bruno Cossermelli; Smith, Julian; Ronquist, Fredrik; Jondelius, Ulf; Hejnol, Andreas (2016). "Xenacoelomorpha is the sister group to Nephrozoa". Nature (Submitted manuscript). 530 (7588): 89–93. Bibcode:2016Natur.530...89C. doi:10.1038/nature16520. PMID 26842059. S2CID 205247296.
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  13. Jiménez-Guri, Eva; Philippe, Hervé; Okamura, Beth; Holland, Peter W. H. (2007-07-06). "Buddenbrockia Is a Cnidarian Worm". Science. 317 (5834): 116–118. Bibcode:2007Sci...317..116J. doi:10.1126/science.1142024. ISSN 0036-8075. PMID 17615357. S2CID 5170702.
  14. Baguñà, Jaume; Martinez, Pere; Paps, Jordi; Riutort, Marta (2008-04-27). "Back in time: a new systematic proposal for the Bilateria". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1496): 1481–1491. doi:10.1098/rstb.2007.2238. ISSN 0962-8436. PMC 2615819. PMID 18192186.
  15. Genikhovich, Grigory; Technau, Ulrich (2017-10-01). "On the evolution of bilaterality". Development. 144 (19): 3392–3404. doi:10.1242/dev.141507. ISSN 0950-1991. PMID 28974637.