Annelid orders

Sabellida is an order of annelid worms formerly in the class Polychaeta. They are filter feeders with no buccal organ. The prostomium is fused with the peristomium and bears a ring of feathery feeding tentacles. They live in parchment-like tubes made of particles from their environment such as sand and shell fragments cemented together with mucus.

Phyllodocida is an order of polychaete worms in the subclass Errantia. These worms are mostly marine, though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cracks and crevices in bedrock. A few construct tubes in which they live and some are pelagic, swimming through the water column. There are estimated to be more than 4,600 accepted species in the order.

Eunicida is an order of polychaete worms.

Branchiobdellida is an order of freshwater leech-like clitellates that are obligate ectosymbionts or ectoparasites, mostly of astacoidean crayfish. They are found in the Northern Hemisphere and have a holarctic distribution in East Asia, the Euro-Mediterranean region and North and Central America, with the greatest species diversity being in North and Central America.

Terebellida make up an order of the Polychaeta class, commonly referred to as "bristle worms". Together with the Sabellida, the Spionida and some enigmatic families of unclear taxonomic relationship (e.g. the Saccocirridae), they make up the subclass Canalipalpata, one of the three main clades of polychaetes. Like most polychaetes, almost all members of the Terebellida are marine organisms. Most are small, sessile detritivores (deposit feeders) which live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorp

The Haplotaxida are one of two orders within the annelid subclass Oligochaeta, the other being the Lumbriculida. No real common name exists, but they are simply referred to as haplotaxids.

Spionida is an order of marine polychaete worms in the infraclass Canalipalpata. Spionids are cosmopolitan and live in soft substrates in the littoral or neritic zones.

Haplodrili, or Archiannelida, is an order of primitive polychaete worms. Zoologist Ray Lankester gave it the name haplodrili, while zoologist Berthold Hatschek later named it Archiannelida. Once considered to be a class under Annelida, and even a separate phylum, Haplodrili is now widely accepted to be an order under Polychaeta. Species in this order are known for completely lacking external segments.

Amphinomida is an order of marine polychaetes. The order contains two families:

Echiuroidea is an order of annelids in the class Polychaeta.

Golfingiida, also known as the Golfingiiformes, is an order of peanut worms. The tentacles form a circle around the mouth, while those of the sister taxon, Phascolosomatidea, are only found above the mouth. Most species burrow in the substrate but some live in the empty shells of gastropods. It is an order of the class Sipuncula (previously considered a phylum), and contains the following families: