The history of Ctenomys in the Fossil Record: A young radiation of an ancient family

Abstract

Ctenomyidae is a clade of South American hystricomorph rodents with a peculiar evolutionary history characterized by: strong morphological differentiation, i.e., modernization that took place in the late Miocene; extinction of lineages during the Plio-Pleistocene, which led to Ctenomys being the only representative of the clade in the living fauna; and an extremely high rate of speciation of the latter genus, which is unmatched among caviomorphs (Reig et al. 1990; Lessa et al. 2008; Verzi 2008; Verzi et al. 2014, 2016; Álvarez et al. 2017, 2020). The stage of morphological differentiation is defned by the acquisition of a unique dental morphology, which persists in living species (Reig 1970). Because of its uniqueness, the appearance of this dental morphology has dictated the recognition of ctenomyids in the fossil record (Wood 1955; Reig et al. 1990; Arnal and Vucetich 2015). In addition, the skeletal morphology of modern ctenomyids diversifed in adjustment to life underground. Because of their unequivocal recognition, as well as their appealing adaptive diversifcation, these modern representatives have attracted the attention of paleontologists almost exclusively; the corpus of information produced, primarily systematic and paleobiological, has provided knowledge on the boundaries of specialization explored by at least part of the clade throughout its history (Reig and Quintana 1992; Casinos et al. 1993; Quintana 1994; Fernández et al. 2000; Vieytes et al. 2007; Lessa et al. 2008; Verzi 2008; Morgan and Verzi 2011).