{{Short description|Order of annelid worms}} {{Automatic taxobox | fossil_range = {{fossil range|Ordovician|recent}} | image = Eunice aphroditois.jpg | image_caption = ''Eunice aphroditois'' | taxon = Eunicida | authority = <ref name=WoRMS>{{cite WoRMS |author=Read, Geoffrey |year=2010 |title=Eunicida |id=895 |access-date=14 March 2026 |db=Polychaeta}}</ref> }}
'''Eunicida''' is an order of polychaete worms.
==Characteristics== Members of this order have an elongated, segmented body and a distinct head, normally with a separate peristomium and prostomium. Many, but not all, live in tubes which vary from a mucous sheath to a tough, horny casing. The palps vary from globular to cylindrical and there are from 0 to 7 antennae, usually smooth but occasionally jointed. There is a muscular pharynx with a dorsal pair of mandibles and a set of ventral, toothed, maxillary plates. Some species have tentacular cirri and all have unbranched parapodia. In some species, dorsal cirri, branchiae, ventral cirri and chaetae occur, but not in others.{{Verify source|date=March 2026}}<ref>[http://www.nhm.ac.uk/research-curation/research/projects/taxinfo/help/eunicida.htm Eunicida] Natural History Museum. Retrieved 2012-01-17.</ref>
==Fossil record== The Devonian ''Websteroprion'' is the largest known fossil eunicidan annelid, with estimated length {{cvt|1|-|2|m}}.<ref name=Erikssonetal2017>{{Cite journal |last1=Eriksson |first1=Mats E. |last2=Parry |first2=Luke A. |last3=Rudkin |first3=David M. |date=February 2017 |title=Earth's oldest 'Bobbit worm' – gigantism in a Devonian eunicidan polychaete |journal=Scientific Reports|volume=7 |issue=2 |pages=239–260 |language=en |doi=10.1038/srep43061|pmid=28220886 |pmc=5318920 |doi-access=free|bibcode=2017NatSR...743061E }}</ref> It also had the biggest scolecodonts of any prehistoric polychaete, up to {{cvt|13.2|mm}} in length and possibly larger.<ref name=Erikssonetal2017/>
==Families== The World Register of Marine Species (WoRMS) includes the following families in the order:<ref name=WoRMS/>
*Dorvilleidae *Eunicidae *Hartmaniellidae *Ichthyotomidae *Lumbrineridae *Oenonidae *Onuphidae
==References== {{Reflist}}
*{{Wikispecies-inline}}
{{Taxonbar|from=Q3060371}} {{Authority control}}
Category:Errantia Category:Annelid orders