A new species of the highly polytypic South American rodent Ctenomys increases the diversity of the magellanicus clade

The subterranean rodent Ctenomys is the most polytypic South American mammal genus and one of the most speciose and rapidly diversifying mammal genera in the world. Its systematics is unstable due to the underlying accelerated diversification processes that give rise to evolutionary lineages at different stages of differentiation and to remarkable morphological homogeneity even among long-differentiated species. As a result, species boundaries are often difficult to define. Diversity of this genus in the coastal area of central Argentina has been extensively studied, with two independent lineages currently recognized while a distinct third population had not been previously detected. Through a phylogenetic analysis based on combined morphological and molecular evidence, Bayesian estimates of divergence times, and morphometric and morphological assessments, we recognize this third population as an independently evolving lineage. The new species, Ctenomys pulcersp. nov., is here described for both the living fauna and the fossil record of the Pampean region of central Argentina. According to phylogenetic results, Ctenomys pulcersp. nov. belongs to the essentially Patagonian magellanicus clade, and would have diverged from its sister species, Ctenomys bidaui, during the middle Pleistocene (ca. 0.4 Ma). Its current distribution in the fixed and semifixed dunes of the coastal Pampean region is assumed to represent a relict of a wider and continuous distribution of potentially suitable environments during the late Pleistocene. Ctenomys pulcersp. nov. occurs in a particularly fragile natural system subjected to profound disturbances caused by diverse anthropic actions and therefore measures for the conservation of its habitat will be indispensable.