A new species of Ancorabolidae (Crustacea: Copepoda: Harpacticoida) from the Campos Basin, Brazil, including a phylogenetic review of the taxon Polyascophorus George, 1998, and a key to its species

A new species of the genus Polyascophorus George, 1998 (Copepoda, Harpacticoida, Ancorabolidae), collected from the Grussaí Canyon (Campos Basin, Brazil, South Atlantic), is described in the present contribution, and increases the number of Polyascophorus species to three. A detailed phylogenetic analysis reveals that Polyascophorus monoceratus sp. nov. shares the following generic apomorphies: (i) lateral posterior cephalic processes bifurcate, (ii) significant diminution of leg 1 endopod, (iii) furcal rami rounded on outer apical margin, and (iv) furcal apical setae IV, V, VI displaced to inner apical edge of furcal ramus. Within the genus, P. monoceratus sp. nov. has five derived characters that justify its establishment as a distinct species: (a) first abdominal somite (genital double-somite in female) with single cuticular process dorsally at posterior margin, (b) branches of female lateral bifurcate cephalic processes of the same size, (c) furcal seta VII plumose on distal half, (d) male leg 1 lacking endopod and (e) apical setae of third exopodal segment of second leg bare and geniculate. While P. gorbunovi ( Smirnov, 1946) and P. martinezi George, 1998 were collected from arctic areas, the finding of P. monoceratus sp. nov. off Brazil extends the generic distributional range to the South Atlantic ocean. A key to the species is provided.