Lyneborgimyia magnifica gen. et sp.n. is described and placed with Merodon Meigen and Platynochaetus Wiedemann in the Merodon genus group within the tribe Eumerini. New morphological characters and terms are introduced, and precise definitions proposed for characters applied inconsistently in the literature. The species possesses several unique autapomorphies, including an additional cross-vein between R₄₊₅ and M₁, and a sclerotized connection between sternite 1 and the metepimeron, which are unknown otherwise within Diptera. A parsimony-based phylogenetic analysis including 73 characters from the adult morphology provides strong support for the monophyly of the Eumerini (Eumerus Meigen, Azpeytia Walker, Lyneborgimyia, Merodon, Platynochaetus) and the Merodon genus group, whereas no support is found for the possible monophyly of the genus Eumerus. A sister-group relationship is indicated between the Afrotropical Lyneborgimyia and the Palaearctic Platynochaetus.