The monotypic Afrotropical genus Prytanomyia Özdikmen, 2006 is revised. Laphystia kochi Lindner, 1973 is found to belong to Prytanomyia and is identical to Prytanomyia albida (Oldroyd, 1974), type of the genus. As a consequence L. kochi is newly combined with Prytanomyia, and P. albida is placed in the synonymy of P. kochi. The species inhabits arid environments, is restricted to the Namib desert from southern Angola to southern Namibia, and is found on vegetated sand mounds and dunes and in dry riverbeds. The highly reduced pulvilli, characteristic of this species, are believed to be an adaptation to living and perching on sandy surfaces. Keywords: Assassin Fly, Robber Fly, Taxonomy, Namib Desert.