The little-known polychaete family Cossuridae is given a detailed taxonomic record from New Zealand for the first time and its sole representative,
Cossura consimilis new species, is described. The dorsal filament of
C. consimilis originates on the anterior part of chaetiger 3, and there are at least 28 anterior-region chaetigers (usually 30). Distribution records are mapped from over 70 locations;
C. consimilis is widespread in the New Zealand region, with most records from the nearshore subtidal, but the species has been found from extreme low water to the mid-continental slope (0-2330 m). The presence of benthic juveniles with extremely long capillaries may indicate a semi-planktonic dispersal phase occurs post-settlement. The taxonomic characters of all cossurid species are tabulated and discussed: the genus
Cossurella is newly synonymized with
Cossura.
