A new genus of coprophagous beetle, Evanesternum gen. n. (Hydrophilidae: Sphaeridiinae: Megasternini), is described in order to accommodate Cercyon (Acycreon) pulsatus d’Orchymont, 1937 from the Republic of South Africa and the Democratic Republic of Congo. A detailed description is provided along with habitus photographs, line drawings and SEM micrographs of relevant diagnostic characters. The new genus possesses the tribal synapomorphies of Megasternini but bears several unique morphological characters which are discussed in detail. The morphology of the remaining three species classified in the subgenus Acycreon d’Orchymont, 1942 (i.e. C. punctiger Knisch, 1921, C. collarti d’Orchymont, 1942 and C. apiciflavus Hebauer, 2002), is illustrated in order to provide evidence that Acycreon is... an assemblage of morphologically dissimilar and likely not related species. An identification key to the Megasternini genera and subgenera known from the Republic of South Africa is presented.