The present contribution provides a taxonomic reassessment of the Lower Cretaceous ammonite species Ammonites crassicostatus d'Orbigny (type species of Colombiceras Spath) and Ammonites gargasensis d'Orbigny (type species of Gargasiceras Casey) from the Aptian type area (Apt, Vaucluse, southeastern France). Those nominal species represent two ornamental poles of a single population, here referred to C. crassicostatum. The genus Gargasiceras is, therefore, synonymised with Colombiceras. Implications on the taxonomy at the specific, generic, and supra-generic levels are discussed.