The genus Ixinandria was described in 1979 to include I. steinbachi from the upper río Juramento in northern Argentina and I. montebelloi from the upper río Bermejo in southern Bolivia. We used a multivariate morphometric analysis (Principal Components Analysis) and a molecular comparison of the Cytochrome Oxidase I gene to investigate variation among distinct populations from the known distribution range of both species. We conclude that the populations are not significantly distinct and do not deserve separate species recognition, and we place I. montebelloi in the synonymy of I. steinbachi.
Neotropical; Synonymy; río Juramento; río Bermejo; río Pilcomayo
