Ctenomys pearsoni is the most karyotypically variable species of the genus (2n=56-70). The goal of this study was to assess the pattern of geographic variation of the skull morphology in several karyomorphs of Ctenomys pearsoni. Our main results indicate that, with the exception of the Solis karyomorph, the remaining are morphologically indistinguishable. These results also agree with previous morphological and population genetics analyses performed in this species. Taken together the available evidence, we support the point of view that not all fixations of chromosomal rearrangement define independent evolutionary units. (C) 2010 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier Gmbh. All rights reserved.