| abstract | The morphological ontogeny of Fuscozetes coulsoni sp. nov. from the High Arctic archipelago of Svalbard (Norway) is described and illustrated. The adult of this species has medium sized translamella, similar to F. kamchatkicus Seniczak et al. 2016a and F. pini Dalenius, 1963, but in F. coulsoni, the lamellar cusp is clearly wider than in other species. The larva of F. coulsoni has a pygidial sclerite, which is unique to Fuscozetes Sellnick, 1928, in other species from this genus the gastronotal shield is uniform, divided in parts, or absent. The juveniles of F. coulsoni and F. kamchatkicus have several similar morphological characters which are rare in Fuscozetes (clavate bothridial seta, dark pigmented sclerite around opisthonotal gland opening, absence of microsclerites at some hysterosomal setae and humeral organ and humeral sclerite in larva), but which are common in Trichoribates Berlese, 1910, except for a humeral sclerite with seta c1 in nymphs, which is present in Fuscozetes and absent in Trichoribates. |