Taxonomy of the genus Ctenomys (Rodentia: Ctenomyidae) in central Argentina: Redefining the limits of Ctenomys bergi Thomas, 1902

Ctenomys Blainville, 1826 (known as tuco-tucos) is considered one of the most diverse genus within mammals; however, its taxonomy is far from resolved. In recent years, new species have been described, and many other forms have been synonymized, while other lineages remain as candidate species. In this work, based on molecular and morphological evidence, we proposed that C. “rosendopascuali”, a taxon considered as a nomen nudum, is in fact a synonym of C. bergi Thomas, 1902. The molecular phylogeny based on the mitochondrial cytochrome b gene showed that individuals from populations a priori assigned to C. bergi and C. “rosendopascuali” were not reciprocally monophyletic. Additionally, geometric morphometric analyses based on cranial morphology showed significant overlap in the morphospace of these two taxa. Our results also show a high genetic similarity among C. bergi, C. “yolandae”, and C. bonettoi Contreras and Berry, 1982, questioning the taxonomic status of the latter two taxa and highlighting the need for exhaustive comparison with C. bergi. We also identified a second locality for a highly divergent lineage within the Mendocinus group (Quijadas lineage). Our study confirms the divergence of this lineage and highlights the need to further taxonomic studies in order to evaluate whether it represents a possible undescribed Ctenomys species.