A new species of Sphaerodoridae (Annelida: Polychaeta), Sphaerodoropsis solis sp. nov., is described from the Challenger Plateau in the Tasman Sea, south-west Pacific. It is the third species of the genus with ventral macrotubercles and is further characterized by the lack of dorsal papillae and the specific arrangement pattern of ventral papillae. A character indicating sexual dimorphism, that has been observed in three morphologically similar species, S. arctowskyensis Hartmann-Schröder & Rosenfeldt, 1988, S. bisphaeroserialis (Hartmann-Schröder, 1974c), and S. garciaalvarezi Moreira, Cacabelos & Troncoso, 2004, is confirmed for S. solis sp. nov. Besides S. solis sp. nov., S. arctowskyensis and S. parva (Ehlers, 1913) are newly recorded from the Challenger Plateau and the East Campbell Plateau in the south-west Pacific. An updated key for the genus Sphaerodoropsis is provided.
