The amphipod family Thaumatelsonidae was established by Gurjanova (1938) on the basis of the existence of special morphological characters in both the antennae and the urosome in certain southern genera of Stenothoidae; the separation of these taxa from the Stenothoidae has, however, been difficult and the family was reduced to subfamily rank by Barnard (1972). The present study confirms the validity of the Thaumatelsoninae, its taxa are shown to be very closely related to each other. A key to those thaumatelsonid genera with a blade-shaped telson of largely or completely vertical orientation is provided, and an additional genus Verticotelson nov.gen. (type V. mantis n.sp.) is erected. Antatelson cuneatum n. sp. is described, and a key to all Antatelson species provided.