Genera are meant to congregate closely related species. Monotypic genera (those that include only one species) represent a paradox and deplete the information content of a classification. The artificial system created by Roewer dictated that every combination of "genus worth characters" should be assigned its own genus. Therefore a great number of species of Opiliones is assigned to monotypic genera. Some of those genera end up gaining more species after many years, such as Roquettea, Soaresia, Rhaucus, although their diagnoses often have to be enlarged to accommodate the newly included species.