A new discussion is proposed on the geographic patterns of distribution presented by the species of the genus Rhopalurus Thorell, inhabiting the savannah formations of the northern South America. Two lineages of Rhopalurus species are defined for this region, each one containing forms with very weak morphological differences, a consequence of only a minor process of differentiation. The observed pattern of distribution and differentiation is suggested to be directly associated with more or less recent palaeoclimatic vicissitudes, which took place in tropical South America during Pleistocene. Two new subspecies are also described, representing new records of Rhopalurus for Brazil and French Guiana.