Polychaeta: Scolecida

Scolecida unique characters : Polychaeta with parapodia with similar rami, with prostomium clearly demarcated, with first segment and its appendages similar to those following, with capillary chaetae, without structures on the head, except for nuchal organs.

Scolecida extended diagnosis: Head usually conical (T-shaped tip in Scalibregmatidae) and lacks palps and other head appendages, although minute eye spots may be present, and a median antenna may be present in Paraonidae. The parapodia lack lobes but have notopodial and neuropodial chaetae as simple capillaries, or capillaries and hooks in the 'Capitellida'. Hooks may be hooded and/or multi-toothed. Cossuridae have a single median gill on an anterior segment and simple segmental gills may be present in other families. The pharynx is eversible as a ventral unarmed, sac-like and usually papillate proboscis which may have finger-like lobes.

Scolecida remarks: The Scolecida comprises the former 'Capitellida' (Arenicolidae, Capitellidae, Maldanidae), together with the Cossuridae, Orbiniidae, Opheliidae, Paraonidae and Scalibregmatidae. Probably not a natural grouping. This group mostly have undemanding lifestyles as conveyor-belt sediment-processors although Cossuridae and Opheliidae may be more selective particulate feeders.

Unique character summary modified after Rouse, G.W.; Pleijel, F. (2001). Polychaetes. Oxford University Press, Oxford. 354 p.

Last modified by G. Read, 21/07/2003 (dd/mm/yy)