Genus Prionospio Malmgren, 1867

Type species: Prionospio steenstrupi Malmgren, 1867 .

Diagnosis (after Peixoto & Paiva 2019): Prostomium anteriorly rounded or truncate, sometimes weakly incised, often with peaks, without frontal horns; subtriangular, rectangular or oval in shape, caruncle extending at least to chaetiger 1; eyespots present or absent; occipital antenna absent. Peristomium at least partially fused with chaetiger 1, often surrounding prostomium with free, flattened lateral wings. Parapodia of chaetiger 1 reduced; noto- and neuropodial lamellae largest in branchial region, reduced thereafter; notopodial lamellae often connected by low to high dorsal ridges or crests. Branchiae from chaetiger 2, 3, or rarely absent. Branchiae limited to anterior chaetigers, 0–15 pairs, rarely more; branchiae all apinnate, all pinnate, or various combinations of both; pinnate branchiae with pinnules digitiform, not platelike; each branchia entirely free from dorsal lamella. Interparapodial pouches present or absent. Anterior chaetae limbate capillaries; posterior noto- and neuropodial hooded hooks present, bi-, tri-, or multidentate, secondary hood present or absent. Neuropodial sabre chaetae present or absent. Pygidium with one long dorsomedial cirrus and two shorter ventrolateral cirri, all three sometimes fused.