There is not enough evidence nor strict cladistic analysis to split the genus into additional genera. Although most of the species can clearly be placed in either of these three groups, some species from one group share morphological characters with species from other groups. Additional studies are necessary, especially those using molecular techniques. As a matter of fact, one of the authors (R. Ferreyra, pers. comm. 1999) does not even agree with the subdivision of Monnina into the three subgenera.