ABSTRACT More than 300 specimens of Paramblypterus duvernoyi from four lakes of the Lower Permian of Germany are examined to determine intra-specific variation of this species and to revise the diagnosis of the genus Paramblypterus. For the first time, a three-dimensional model of the skull and the snout of Paramblypterus is reconstructed. A partial tooth bearing premaxilla, which forms the anterior most part of the gape, is described; in contrast, the absence of a premaxilla had until now been considered a synapomorphy of the genus Paramblypterus. Information obtained from the study of P. duvernoyi has required a new revision of Paramblypterus gelberti. A comparison between the two species indicates a very similar morphology and they may belong to a single species. The study of their intra-specific variation has shown only minor differences, which may be explained by heterochrony. Both Paramblypterus duvernoyi and Paramblypterus gelberti are highly variable concerning the number and arrangement of certai...