The oldest species of Dolichotis (Rodentia, Hystricognathi) from the pliocene of Argentina: redescription and taxonomic status of “Orthomyctera” chapalmalense

Abstract

The Subfamily Dolichotinae comprises two living species, Dolichotis patagonum, an emblematic component of the Patagonian fauna of Argentina, and Dolichotis salinicola, endemic to the Chaco ecoregion. These two species are also considered as pertaining to different genera, D. patagonum and Pediolagus salinicola. The oldest records of Dolichotis come from the Pliocene–Pleistocene boundary of northeastern and central Argentina, and the late Pleistocene from southern Brazil, and northern and southern Uruguay. Five fossil species were described from the Pleistocene and Holocene in central Argentina (D. minor, D. plathycephala, D. major, D. intermedia, and D. improla). “Orthomyctera” chapalmalense was described on the basis of remains from the coast of Mar del Plata and Chapadmalal, Buenos Aires Province, Chapadmalal Formation (late Pliocene, 3.74–3.04 Ma). A new detailed description of the holotype and its comparison with closely related taxa suggests that this species is more related to the genus Dolichotis, resulting in the new combination D. chapalmalense. The close affinities with Dolichotis revealed by phylogenetic analyses combined with molecular and morphological characters were corroborated in previous analyses. The origin of this lineage extends at least to a million years ago, taking the record back to the middle Pliocene. The evolutionary novelties that appear at least since the Pliocene, marking a key period for the Caviidae, are analyzed. Based on a phylogenetic perspective with the inclusion of the fossil record, our data support the inclusion of the two species (D. patagonum and D. salinicola) in a single genus.