Syndermata
{{Short description|Clade of animals}}
{{Refimprove|date=June 2022}}
{{Automatic taxobox
| image = Mikrofoto.de-Raedertier-14.jpg
| image_caption = Rotifer
| image2 = C wegeneri.JPG
| image2_caption = Acanthocephalan
| classification_status = disputed
| taxon = Syndermata
| authority = Zrzavý, 1998
| subdivision_ranks = Phyla
| subdivision =
}}
Syndermata is a clade of animals that, in some systems, is considered synonymous with Rotifera. Older systems separate Rotifera and Acanthocephala as different phyla, and group them both under Syndermata.{{Citation |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard S. |last3=Barnes |first3=Robert D. |year=2004 |title=Invertebrate Zoology : a functional evolutionary approach |edition=7th |location=Belmont, CA |publisher=Thomson-Brooks/Cole |isbn=978-0-03-025982-1 |url-access=registration |url=https://archive.org/details/isbn_9780030259821 }}, p. 788ff. – see particularly p. 804{{cite journal | last1=Perrot-Minnot | first1=Marie-Jeanne | last2=Cozzarolo | first2=Camille-Sophie | last3=Amin | first3=Omar | last4=Barčák | first4=Daniel | last5=Bauer | first5=Alexandre | last6=Filipović Marijić | first6=Vlatka | last7=García-Varela | first7=Martín | last8=Servando Hernández-Orts | first8=Jesús | last9=Yen Le | first9=T.T. | last10=Nachev | first10=Milen | last11=Orosová | first11=Martina | last12=Rigaud | first12=Thierry | last13=Šariri | first13=Sara | last14=Wattier | first14=Rémi | last15=Reyda | first15=Florian | last16=Sures | first16=Bernd | title=Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala | journal=Parasite | volume=30 | year=2023| doi=10.1051/parasite/2023026 | page=23| pmid=37350678 | pmc=10288976 }} {{open access}}{{Cite web |title=Syndermata |url=https://comenius.susqu.edu/biol/202/animals/protostomes/spiralia/platyzoa/syndermata/default.htm |access-date=2022-06-06 |website=comenius.susqu.edu}} This clade is placed in the Platyzoa.
Phylogeny
Phylogenetic analysis of the 18S ribosomal gene has revealed that the Acanthocephala, formerly considered a separate phylum are most closely related to the rotifers. They are possibly closer to the two rotifer classes Bdelloidea and Monogononta than to the other class, Seisonidea, producing the names and relationships shown in the cladogram below.{{citation needed|date=July 2023}}
{{clade|{{clade
|label1=Syndermata
|1={{clade
|1=Seisonida
|2={{clade
|label1=Eurotatoria
|1={{clade
|1=Bdelloidea
|2=Monogononta
}}
}}
}}
}}|style=line-height:100%}}
A study of the gene order in the mitochondria suggests that Seisonidea and Acanthocephala are sister clades and that the Bdelloidea are the sister clade to this group.{{cite journal |last1=Sielaff |first1=M. |last2=Schmidt |first2=H. |last3=Struck |first3=T. H. |last4=Rosenkranz |first4=D. |last5=Mark Welch |first5=D. B. |last6=Hankeln |first6=T |last7=Herlyn |first7=H. |date=March 2016 |title=Phylogeny of Syndermata (syn. Rotifera): Mitochondrial gene order verifies epizoic Seisonidea as sister to endoparasitic Acanthocephala within monophyletic Hemirotifera |journal=Molecular Phylogenetics and Evolution |volume=96 |pages= 79–92|doi=10.1016/j.ympev.2015.11.017 |pmid=26702959 }} This has since been corroborated by the discovery of a fossil stem-group acanthocephalan.{{cite journal | last=Luo | first=Cihang | last2=Parry | first2=Luke A. | last3=Boudinot | first3=Brendon E. | last4=Wang | first4=Shengyu | last5=Jarzembowski | first5=Edmund A. | last6=Zhang | first6=Haichun | last7=Wang | first7=Bo | title=A Jurassic acanthocephalan illuminates the origin of thorny-headed worms | journal=Nature | date=2025-04-09 | issn=0028-0836 | doi=10.1038/s41586-025-08830-5 | url=https://www.nature.com/articles/s41586-025-08830-5 | access-date=2025-04-10 | page=| url-access=subscription }}