Most genera have no gills (if present, they are usually branched and arise on mid-anterior segments of body).

Unlike bone and tooth enamel, this is not mineralised with calcium, but is formed by a histidine rich protein, with bound zinc ions.

Their closest neighbours in polychaete phylogenetic tree are Chrysopetalidae and Hesionidae (the superfamily Nereidoidea).

They are commonly found in all water depths, foraging in seaweeds, hiding under rocks or burrowing in sand or mud.

[6] Ragworms, such as Tylorrhynchus heterochetus, are considered a delicacy in Vietnam where they are used in the dish chả rươi.

[7] In rice-growing areas of China, these worms are called 禾虫 (Mandarin: hé chóng, Cantonese: woh4 chuhng4).