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The prostomium is rounded or pointed, and is generally without appendages, except for one small antenna in species of Tainokia, and three in species of Oenone and Halla; eyespots may be present at the posterior margin. The peristomium may consist of one or two rings. Parapodia are sub-biramous. The notopodia are represented by button-like to lamellate lobes (dorsal cirri) with internal aciculae. Branchiae are absent. The neuropodial chaetae are simple limbate; in some genera additional bidentate subacicular hooks or large spines are present. Ventral cirri are absent; pygidial cirri number two to four. The mandibles are unfused, lack visible growth rings, and may be reduced or absent in some species. The maxillae are unmineralised, and are generally composed of five pairs of plates and long, slender carriers often with a ventral ligament (or ‘third carrier’). The maxillary plates are asymmetrical in species of Oenone and Notocirrus where the first right maxillary element is a ‘basal plate’ and the right maxilla III is lacking. This is common in extinct labidognath and prionognath jaws, but is not found in any other extant eunicidan family. The maxillae may be reduced or absent in some parasitic species.

The above description is based on Paxton (2000), which in turn is based on Fauchald & Rouse (1997).

Identification tips

Recognising the family
Oenonids are typically large worms which burrow in sand and mud, but a number of species are parasitic. They resemble lumbrinerids in resembling earthworms but can be distinguished from them by the presence of a flattened head.

Distinguishing species
RW ... need dissection instructions (same for all Eunicida) ...

Species of Oenonidae can be distinguished using such characters as the shape of the prostomium, the type and distribution of chaetae and the shape of the dorsal cirri. The development of the maxillae is important in free living species but may be reduced or absent in parasitic species. The presence of a small antenna defines the genus Tainokia; this is absent in all other genera.


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