The present paper is a supplement to an earlier revision of the genus Onymacris Allard (Coleoptera: Tenebrionidae) by the author in 1975. A new species, Onymacris brainei spec. nov., and a new subspecies, O. unguicularis schulzeae subspec. nov., are described. Recently collected material of O. candidipennis (Breme) and O. paiva (Haag), representing range extensions, is discussed. A key to all species and subspecies is given, the distribution of all species is mapped to illustrate several range extensions, and the phylogenetic relationships of the species are analysed. Keywords: Coleoptera, Desert dune beetles, Onymacris Allard, Phylogenetic relationships and Tenebriodinae.