Small to large; whitish, yellowish brown to brown, or orange in colour. Head capsule rarely more than 1.5 times as long as wide; yellowish brown to dark brown or black, usually with strongly contrasting black occipital margin, sometimes with expanded collar; with few widely spaced setae, or in Protanypodini, with numerous closely spaced short setae; postoccipital margin in Protanypodini with long ventrolateral, posteriorly-directed projections on each side. Eye spot single to weakly bilobed, if (rarely) separate, then dorsal eye-spot posterior to ventral eye spot.
Frontoclypeal apotome and labral sclerite often weakly separated. Dorsal surface smooth except tuberculose in Boreoheptagyini.
Non-retractile, mounted on head capsule, or sometimes on short pedestal; shorter than mandibular length; 4-5 segmented; segment 3 usually annulated. Ring organ on basal 1/2 or (rarely) mid basal segment. Blade shorter than flagellum; accessory blade well developed. Lauterborn organs small to well developed, shorter than style.
SI seta simple, seta-like to taeniate; SII simple; SIII simple, or bifid, rarely branched; SIVA and B present. Labral lamellae present or absent. Chaetae absent to numerous; chaeta media often differentiated from remaining chaetae; spinulae present. Pecten epipharyngis consisting 3, 5 or 7 scales. 4-7 pairs of chaetulae laterales; chaetulae basales 2 simple or terminally notched pairs. Premandible with 1-16 teeth; without brush; lateral spine present or absent.
With single apical tooth and 4-5 inner teeth. Pecten mandibularis absent. Seta subdentalis usually short, rarely extending beyond apex of last inner tooth. Seta interna usually fan-shaped, with up to 30 branches, sometimes absent.
Highly variable in shape, with 4-23 teeth, or rarely without teeth. Ventromental plates vestigial to large, sometimes fused medially and forming ventral surface of mentum; beard absent. Setae submenti usually arising near mentum, rarely displaced posteriorly.
Palp with about 10-11 sensillae. Palpiger with chaetulae. Galea with 5-6 sensillae, usually with lamellae; without pecten galearis. Laciniae short, with overlapping long chaetulae; appendix seta apparently absent. Usually 4 pairs of simple setae maxillaris, occasionally 9-16 anterior setae pairs present, or medial seta (SM1) bifid.
Parapods well developed, usually separated and with apical crown of claws, sometimes anterior parapods fused with divided apex; apical claws usually irregularly arranged, sometimes in a circle. Procercus present or absent; anal setae present. Supra-anal seta present. Anal tubules 2 pairs, shorter than posterior parapods; 1 tubule of ventral pair sometimes directed distoventrally and extending ventrally between bases of posterior parapods. Anal end usually directed posteriorly, sometimes bent ventrally. Body setae simple, usually pale, short and indistinct, rarely dark long and conspicuous. In Boreoheptagyini, body with simple to multipointed spines or coarse bars arising from clear central area; sometimes abdominal segments with 2 pairs of dorsolateral tubercles on each side.