Taxonomy and Systematics
Taxonomically, polychaetes are thought to be paraphyletic, meaning that the group excludes some descendants of its most recent common ancestor. Groups that may be descended from the polychaetes include the oligochaetes (earthworms and leeches), sipunculans, and echiurans. 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 given below were shown to be mostly paraphyletic in recent years.
- Subclass Palpata
- Order Aciculata
- Basal or incertae sedis
- Family Aberrantidae
- Family Nerillidae
- Family Spintheridae
- Suborder Eunicida
- Family Amphinomidae
- Family Diurodrilidae
- Family Dorvilleidae
- Family Eunicidae
- Family Euphrosinidae
- Family Hartmaniellidae
- Family Histriobdellidae
- Family Lumbrineridae
- Family Oenonidae
- Family Onuphidae
- Suborder Phyllodocida
- Family Acoetidae
- Family Alciopidae
- Family Aphroditidae
- Family Chrysopetalidae
- Family Eulepethidae
- Family Glyceridae
- Family Goniadidae
- Family Hesionidae
- Family Ichthyotomidae
- Family Iospilidae
- Family Lacydoniidae
- Family Lopadorhynchidae
- Family Myzostomatidae
- Family Nautillienellidae
- Family Nephtyidae
- Family Nereididae
- Family Paralacydoniidae
- Family Pholoidae
- Family Phyllodocidae
- Family Pilargidae
- Family Pisionidae
- Family Polynoidae
- Family Pontodoridae
- Family Sigalionidae
- Family Sphaeodoridae
- Family Syllidae
- Family Typhloscolecidae
- Family Tomopteridae
- Basal or incertae sedis
- Order Canalipalpata
- Basal or incertae sedis
- Family Polygordiidae
- Family Protodrilidae
- Family Protodriloididae
- Family Saccocirridae
- Suborder Sabellida
- Family Oweniidae
- Family Siboglinidae (formerly the phyla Pogonophora & Vestimentifera)
- Family Serpulidae
- Family Sabellidae
- Family Sabellariidae
- Family Spirorbidae
- Suborder Spionida
- Family Apistobranchidae
- Family Chaetopteridae
- Family Longosomatidae
- Family Magelonidae
- Family Poecilochaetidae
- Family Spionidae
- Family Trochochaetidae
- Family Uncispionidae
- Suborder Terebellida
- Family Acrocirridae (sometimes placed in Spionida)
- Family Alvinellidae
- Family Ampharetidae
- 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 Pectinariidae
- Family Poeobiidae (sometimes own suborder Poeobiida or included in Flabelligerida)
- Family Sternaspidae (sometimes own suborder Sternaspida)
- Family Terebellidae
- Family Trichobranchidae
- Basal or incertae sedis
- Order Aciculata
- Subclass Scolecida
- Family Aeolosomatidae
- Family Arenicolidae
- Family Capitellidae
- Family Cossunidae
- Family Maldanidae
- Family Opheliidae
- Family Orbiniidae
- Family Paraonidae
- Family Parergodrilidae
- Family Potamodrilidae
- Family Psammodrilidae
- Family Questidae
- Family Scalibregmatidae
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