A revision of the cladistic analysis presented by Rodríguez and Pereira (1992) for the species of the genus Fredius Pretzmann, 1967 (Pseudothelphusidae), was carried out using additional species and new homologies to obtain a more robust cladogram. The tree obtained differs from the previous one in the clustering of species, but the area cladogram confirms a previous theory on the plausible evolution of the group in the Guianan lowlands of South America, between the Orinoco and the Amazon rivers. A new species is described from Colombia, extending considerably the range of the genus into the upper Amazon basin. A key to all species in the genus is given.