Editing Polychaete (section)

==Taxonomy and systematics==
{{see also|List of annelid families}}
[[File:Phyllodoce lineata.jpg|thumb| Head of ''Phyllodoce lineata'']]
[[File:Pacific Feather Duster Sabellastarte sp.jpg|thumb|right| The plumes of the [[feather duster worm]] are used to filter water]]
[[File:Tomopteriskils.jpg|thumb|right| [[Planktonic]] bristleworm ''[[Tomopteris]]'']]
[[File:Spirobrancheus giganteus.jpg|thumb| [[Christmas tree worm]]s]]
[[File:Nereis pelagica.jpg|thumb| [[Rag worm]]s can be dangerous to touch, giving painful burns]]
[[File:Nereis virens.jpg|thumb| [[Alitta virens|Sandworms]] eat seaweed and microorganisms and can be longer than  four feet]]
[[File:Riftia tube worm colony Galapagos 2011.jpg|thumb| [[Giant tube worm]]s can tolerate extremely high hydrogen sulfide levels]]

Taxonomically, polychaetes are thought to be [[paraphyletic]],<ref>{{cite journal |last=Westheide |first=W. |year=1997 |title=The direction of evolution within the Polychaeta |journal=Journal of Natural History |volume=31 |issue=1 |pages=1–15 |doi=10.1080/00222939700770011 |bibcode=1997JNatH..31....1W }}</ref> meaning the group excludes some descendants of its most recent common ancestor.  Groups that may be descended from the polychaetes include the [[clitellate]]s ([[earthworm]]s and [[leech]]es), [[sipuncula]]ns, and [[echiura]]ns.  The Pogonophora and [[Vestimentifera]] were once considered separate phyla, but are now classified in the polychaete family [[Siboglinidae]].

Much of the classification below matches Rouse & Fauchald, 1998, although that paper does not apply ranks above family.

Older classifications recognize many more (sub)orders than the layout presented here. As comparatively few polychaete [[taxa]] have been subject to [[cladistic]] analysis, some groups which are usually considered invalid today may eventually be reinstated.

These divisions were shown to be mostly paraphyletic in recent years.

*'''[[Basal (evolution)|Basal]] or ''[[incertae sedis]]'''''
**Family [[Diurodrilidae]]
**Family [[Histriobdellidae]]
**Family [[Nerillidae]]
**Family [[Parergodrilidae]]
**Family [[Potamodrilidae]]
**Family [[Psammodrilidae]]
**Family [[Spintheridae]]
**Family [[Protodriloididae]]
**Family [[Saccocirridae]]
**Order [[Haplodrili]]
**Order [[Myzostomida]]
***Family [[Endomyzostomatidae]]
***Family [[Asteromyzostomatidae]]
***Family [[Myzostomatidae]]
*'''Subclass [[Palpata]]'''
**Family [[Protodrilidae]]
**Family [[Polygordiidae]]
*'''Subclass [[Aciculata]]'''
**Family [[Levidoridae]]
**Order [[Amphinomida]]
***Family [[Amphinomidae]]
***Family [[Euphrosinidae]]
**Order [[Eunicida]]
***Family [[Dorvilleidae]]
***Family [[Eunicidae]]
***Family [[Hartmaniellidae]]
***Family [[Ichthyotomidae]]
***Family [[Lumbrineridae]]
***Family [[Oenonidae]]
***Family [[Onuphidae]]
**Order [[Phyllodocida]]
***Suborder [[Aphroditiformia]]
****Family [[Acoetidae]]
****Family [[Aphroditidae]]
****Family [[Eulepethidae]]
****Family [[Iphionidae]]
****Family [[Pholoidae]]
****Family [[Polynoidae]]
****Family [[Sigalionidae]]
***Suborder [[Glyceriformia]]
****Family [[Glyceridae]]
****Family [[Goniadidae]]
****Family [[Lacydoniidae]]
****Family [[Paralacydoniidae]]
***Suborder [[Nereidiformia]]
****Family [[Antonbruunidae]]
****Family [[Chrysopetalidae]]
****Family [[Hesionidae]]
****Family [[Nereididae]]
****Family [[Pilargidae]]
****Family [[Syllidae]]
***Suborder [[Phyllodocida incertae sedis]]
****Family [[Iospilidae]]
****Family [[Nautiliniellidae]]
****Family [[Nephtyidae]]
****Family [[Typhloscolecidae]]
****Family [[Tomopteridae]]
***Suborder [[Phyllodociformia]]
****Family [[Alciopidae]]
****Family [[Lopadorrhynchidae]]
****Family [[Phyllodocidae]]
****Family [[Pontodoridae]]
*'''Subclass [[Sedentaria]]'''
**Family [[Chaetopteridae]]
**Infraclass [[Canalipalpata]]
***Order [[Sabellida]]
****Family [[Caobangidae]]
****Family [[Fabriciidae]]
****Family [[Oweniidae]]
****Family [[Sabellariidae]]
****Family [[Sabellidae]]
****Family [[Serpulidae]]
****Family [[Siboglinidae]] (formerly the phyla Pogonophora & Vestimentifera)
***Order [[Spionida]]
****Suborder [[Spioniformia]]
*****Family [[Apistobranchidae]]
*****Family [[Longosomatidae]]
*****Family [[Magelonidae]]
*****Family [[Poecilochaetidae]]
*****Family [[Spionidae]]
*****Family [[Trochochaetidae]]
*****Family [[Uncispionidae]]
***Order [[Terebellida]]
****Suborder [[Cirratuliformia]]
*****Family [[Acrocirridae]] (sometimes placed in Spionida)
*****Family [[Cirratulidae]] (sometimes placed in Spionida)
*****Family [[Ctenodrilidae]] (sometimes own suborder Ctenodrilida)
*****Family [[Fauveliopsidae]] (sometimes own suborder Fauveliopsida)
*****Family [[Flabelligeridae]] (sometimes suborder Flabelligerida)
*****Family [[Flotidae]] (sometimes included in Flabelligeridae)
*****Family [[Poeobiidae]] (sometimes own suborder Poeobiida or included in Flabelligerida)
*****Family [[Sternaspidae]] (sometimes own suborder Sternaspida)
****Suborder [[Terebellomorpha]]
*****Family [[Alvinellidae]]
*****Family [[Ampharetidae]]
*****Family [[Pectinariidae]]
*****Family [[Terebellidae]]
*****Family [[Trichobranchidae]]
**Infraclass [[Scolecida]]
***Family [[Arenicolidae]]
***Family [[Capitellidae]]
***Family [[Cossuridae]]
***Family [[Maldanidae]]
***Family [[Opheliidae]]
***Family [[Orbiniidae]]
***Family [[Paraonidae]]
***Family [[Scalibregmatidae]]
***Order [[Capitellida]] ([[nomen dubium]])
***Order [[Cossurida]] (nomen dubium)
***Order [[Opheliida]] (nomen dubium)
***Order [[Orbiniida]] (nomen dubium)
***Order [[Questida]] (nomen dubium)
***Order [[Scolecidaformia]] (nomen dubium)
*'''Subclass [[Echiura]]'''
** Order [[Bonelliida]]
*** Family [[Bonelliidae]] 
*** Family [[Ikedidae]] 
** Order [[Echiurida]]
*** Family [[Echiuridae]] 
*** Family [[Thalassematidae]] 
*** Family [[Urechidae]]