Editing Sipuncula (section)

==Taxonomy==
{{See also|List of bilaterial animal orders}}
{{lang|la|Sipuncula}} is a [[feminine (grammar)|feminine]] variant of the now-obsolete [[genus name]] {{lang|la|[[Sipunculus]]}}, itself a variant of the [[Latin language|Latin]] {{lang|la|{{linktext|siphunculus}}}} ("little tube"),<ref>{{cite web |url=https://en.oxforddictionaries.com/definition/sipuncula |title=Sipuncula |work=Oxford Living Dictionaries |publisher=Oxford University Press |access-date=10 February 2019 |archive-url=https://web.archive.org/web/20190212011749/https://en.oxforddictionaries.com/definition/sipuncula |archive-date=12 February 2019 |url-status=dead }}</ref> a [[Diminutive (linguistics)|diminutive]] of {{lang|la|sipho}} from [[Ancient Greek language|Greek]] {{lang|grc|{{linktext|σίφων}}}} (''síphōn'', "[[tube (fluid conveyance)|tube]], [[pipe (fluid conveyance)|pipe]]").

The Swedish naturalist [[Carl Linnaeus]] first described the worm {{lang|la|[[Sipunculus nudus]]}} in his {{lang|la|Systema Naturae}} in 1767.<ref>{{cite WoRMS |author=Saiz-Salinas, José |year=2009 |title=''Sipunculus (Sipunculus) nudus'' Linnaeus, 1766 |id=136084 |access-date=27 February 2019}}</ref> In 1814, the French zoologist [[Constantine Samuel Rafinesque]] used the word "Sipuncula" to describe the family (now [[Sipunculidae]]),<ref name="Rafinesque">{{cite book|author=Rafinesque, Constantine Samuel |title=Précis des découvertes et travaux somiologiques de m.r C. S. Rafinesque-Schmaltz entre 1800 et 1814 ou Choix raisonné de ses principales découvertes en zoologie et en botanique|url=https://archive.org/details/prcisdesdcouvert00rafi |year=1814 |publisher=Royale typographie militaire, aux dépens de l'auteur|page=[https://archive.org/details/prcisdesdcouvert00rafi/page/32 32]}}</ref> and in time, the term came to be used for the whole class.<ref>{{cite WoRMS  |year=2018 |title=Sipuncula |id=1268 |access-date=27 February 2019}}</ref> This is a relatively understudied group, and it is estimated there may be around 162 species worldwide.<ref name=Pancucci>{{cite web |url=https://okeanos-dspace.hcmr.gr/bitstream/handle/123456789/114/Monograph_02_The_Phylum_Sipuncula.pdf?sequence=1 |title=The phylum Sipuncula in the Mediterranean Sea |author1=Pancucci-Papadopoulou, M.A. |author2=Murina, G.V.V. |author3=Zenetos, A. |year=2014 |publisher=National Centre for Marine Research |access-date=10 February 2019 |archive-url=https://web.archive.org/web/20190212130746/https://okeanos-dspace.hcmr.gr/bitstream/handle/123456789/114/Monograph_02_The_Phylum_Sipuncula.pdf?sequence=1 |archive-date=12 February 2019 |url-status=dead }}</ref>

The [[phylogenetics|phylogenetic]] placement of this group in the past has proved troublesome. Originally classified as [[annelid]]s, despite the complete lack of segmentation, [[bristle]]s and other annelid characters, the phylum Sipuncula was later allied with the [[Mollusca]], mostly on the basis of [[morphogenesis|development]]al and [[larva]]l characters. These phyla have been included in a larger group, the [[Lophotrochozoa]], that also includes the [[annelid]]s, the [[nemertea|ribbon worms]] and several other phyla. Phylogenetic analyses based on 79 ribosomal proteins indicated a position of Sipuncula within Annelida.<ref name="Struck2011">{{Cite journal | last1 = Struck | first1 = T. H. | last2 = Paul | first2 = C. | last3 = Hill | first3 = N. | last4 = Hartmann | first4 = S. | last5 = Hösel | first5 = C. | last6 = Kube | first6 = M. | last7 = Lieb | first7 = B. | last8 = Meyer | first8 = A. | last9 = Tiedemann | first9 = R. | last10 = Purschke | doi = 10.1038/nature09864 | first10 = G. N. | last11 = Bleidorn | first11 = C. | title = Phylogenomic analyses unravel annelid evolution | journal = Nature | volume = 471 | issue = 7336 | pages = 95–98 | date = 3 March 2011 | pmid =  21368831| bibcode = 2011Natur.471...95S | s2cid = 4428998 }}</ref><ref name="Hausdorf2007">{{cite journal | last1 = Hausdorf | first1 = B. | display-authors = etal   | year = 2007 | title = Spiralian Phylogenomics Supports the Resurrection of Bryozoa Comprising Ectoprocta and Entoprocta | journal = Molecular Biology and Evolution | volume = 24 | issue = 12| pages = 2723–2729 | doi=10.1093/molbev/msm214 | pmid=17921486| doi-access = free }}</ref> Subsequent analysis of the [[mitochondrion]]'s DNA has confirmed their close relationship to the Annelida (including [[echiura]]ns and [[Siboglinidae|pogonophorans]]).<ref name="Shen2009">{{Cite journal | doi = 10.1186/1471-2164-10-136| title = A close phylogenetic relationship between Sipuncula and Annelida evidenced from the complete mitochondrial genome sequence of Phascolosoma esculenta| journal = BMC Genomics| volume = 10| pages = 136| year = 2009| last1 = Shen | first1 = X. | last2 = Ma | first2 = X. | last3 = Ren | first3 = J. | last4 = Zhao | first4 = F. | pmid=19327168 | pmc=2667193| doi-access = free}}</ref> It has also been shown that a rudimentary neural segmentation similar to that of annelids occurs in the early larval stage, even if these traits are absent in the adults.<ref>{{cite journal |first1=Andreas |last1=Wanninger |first2=Alen |last2=Kristof |first3=Nora |last3=Brinkmann |title=Sipunculans and segmentation |journal=Communicative and Integrative Biology |date=Jan–Feb 2009 |volume=2 |issue=1 |pages=56–59 |pmc=2649304 |pmid=19513266 |doi=10.4161/cib.2.1.7505}}</ref>