Editing Flatworm (section)

==Evolution==

An outline of the origins of the parasitic lifestyle has been proposed;<ref name=Perkins2010>{{cite journal |last1=Perkins |first1=EM |last2=Donnellan |first2=SC |last3=Bertozzi |first3=T |last4=Whittington |first4=ID |year=2010 |title=Closing the mitochondrial circle on paraphyly of the Monogenea (Platyhelminthes) infers evolution in the diet of parasitic flatworms |journal=Int J Parasitol |volume=40 |issue=11|pages=1237–45 |doi=10.1016/j.ijpara.2010.02.017 |pmid=20493870 }}</ref> epithelial feeding [[monopisthocotylea]]ns on fish hosts are basal in the Neodermata and were the first shift to parasitism from free living ancestors. The next evolutionary step was a dietary change from [[epithelium]] to [[blood]]. The last common ancestor of Digenea + Cestoda was monogenean and most likely sanguinivorous.

In several members of the order [[Rhabdocoela]] an [[Endosymbiont|endosymbiotic]] relationship with [[microalgae]] has evolved. Some species in the same order has also evolved [[kleptoplasty]].<ref>{{Cite journal|title=A new case of kleptoplasty in animals: Marine flatworms steal functional plastids from diatoms|first1=Niels W. L.|last1=Van Steenkiste|first2=India|last2=Stephenson|first3=María|last3=Herranz|first4=Filip|last4=Husnik|first5=Patrick J.|last5=Keeling|first6=Brian S.|last6=Leander|date=July 5, 2019|journal=Science Advances|volume=5|issue=7|doi=10.1126/sciadv.aaw4337|pmid=31328166|pmc=6636991}}</ref>

The earliest known fossils confidently classified as tapeworms have been dated to {{Ma|270}}, after being found in [[coprolite]]s (fossilised faeces) from an [[elasmobranch]].<ref name="Dentzien-Dias2013">{{cite journal |last1=Dentzien-Dias |first1=PC |last2=Poinar |first2=G Jr |last3=de Figueiredo |first3=AE |last4=Pacheco |first4=AC |last5=Horn |first5=BL |last6=Schultz |first6=CL |date=30 January 2013 |title=Tapeworm eggs in a 270 million-year-old shark coprolite |journal=PLOS ONE |volume=8 |issue=1|page=e55007 |doi=10.1371/journal.pone.0055007 |pmid=23383033 |pmc=3559381|bibcode=2013PLoSO...855007D |doi-access=free }}</ref> Putative older fossils include a ribbon-shaped, bilaterally symmetrical organism named ''[[Rugosusivitta]] orthogonia'' from the Early Cambrian of [[China]],<ref name=Rugosusivitta>{{Cite journal|last1=Tang |first1=F. |last2=Song |first2=S. |last3=Zhang |first3=G. |last4=Chen |first4=A. |last5=Liu |first5=J. |title=Enigmatic ribbon-like fossil from Early Cambrian of Yunnan, China |year=2021 |journal=China Geology |volume=4 |issue=2 |pages=205–214 |doi=10.31035/cg2020056 |bibcode=2021CGeo....4..205T |doi-access=free }}</ref> brownish bodies on the bedding planes reported from the Late [[Ordovician]] ([[Katian]]) [[Vaureal Formation|Vauréal Formation]] ([[Canada]]) by Knaust & Desrochers (2019), tentatively interpreted as turbellarians (though the authors cautioned that they might ultimately turn out to be fossils of [[Acoelomorpha|acoelomorphs]] or [[nemertea]]ns)<ref name=GRKnaustDesrochers>{{Cite journal|author1=Dirk Knaust |author2=André Desrochers |year=2019 |title=Exceptionally preserved soft-bodied assemblage in Ordovician carbonates of Anticosti Island, eastern Canada |journal=Gondwana Research |volume=71 |pages=117–128 |doi=10.1016/j.gr.2019.01.016 |bibcode=2019GondR..71..117K |s2cid=134814852 }}</ref> and circlets of fossil hooks preserved with [[Placodermi|placoderm]] and [[Acanthodii|acanthodian]] fossils from the [[Devonian]] of [[Latvia]], at least some of which might represent parasitic monogeneans.<ref>{{cite book |author1=Kenneth De Baets |author2=Paula Dentzien-Dias |author3=Ieva Upeniece |author4=Olivier Verneau |author5=Philip C.J. Donoghue |year=2015 |chapter=Constraining the deep origin of parasitic flatworms and host-interactions with fossil evidence |editor1=Kenneth De Baets |editor2=D. Timothy J Littlewood |title=Fossil parasites |series=Advances in Parasitology |volume=90 |pages=93–135 |doi=10.1016/bs.apar.2015.06.002 |pmid=26597066 |isbn=9780128040010 |s2cid=7278956 |issn=0065-308X |url=https://hal-univ-perp.archives-ouvertes.fr/hal-01257074/file/debaets2015.pdf |access-date=2022-07-15 |archive-date=2022-07-30 |archive-url=https://web.archive.org/web/20220730040408/https://hal-univ-perp.archives-ouvertes.fr/hal-01257074/file/debaets2015.pdf |url-status=live }}</ref>