Ideorhipistena occipitalis, new genus, new species, from Bismarck Archipelago (Papua-New Guinea), is described and included in the family Mordellidae. Though definitely fitting within the ground plan of Mordellidae, it superficially resembles Rhipistena Sharp (Rhipiphoridae, subfam. Pelecotominae) as a result of convergence. Ideorhipistena displays characters so far unknown in Mordellidae, including quite protruding occipital margin, strongly developed temples, long prothoracic neck, narrow elytral epipleura, pronotum without anterior and posterior angles, strongly protruding at its hind margin. These justify its position as a distinct genus, in the key to world genera of the tribe Mordellini.