Oxymorostes riedeli new genus and species is described from the Indonesian part of New Guinea. This new taxon is characterized by a number of unique characters: the presence of a deep excavation in the hypomeron and the unusually modified humeral area of the elytra. Its closest relationships seem to be within the newly defined “Perignamptus genus group”, characterized by mouthparts morphology, including the presence of a large pore on the mandibular surface. This group gathers at least the Oriental/Australasian genera Madrasostes Paulian, Perignamptus Harold, and Macrophilharmostes Paulian as well as a few species currently placed in other genera.