The fossil record of chinchilla rats (Abrocomidae, Hystricomorpha) from the Late Miocene-Early Pliocene of southern South America

This study analyses the taxonomy and diversity of Late Miocene-Early Pliocene Abrocomidae, from southern South America, in the comparative context of living genera and species of the family. Through qualitative analysis of dental and skeletal morphology (including endocranial features) and morphometric examination of molars, we identify one extinct genus, Protabrocoma, comprising three species: the previously described P. paranensis and P. antiqua, along with the newly identified Protabrocoma chasicoensis sp. nov. Although the variation observed in Protabrocoma exceeds that of living genera within the family, we conservatively limit the Late Miocene-Early Pliocene radiation to a single genus until a comprehensive phylogenetic analysis of all living and extinct species is conducted. Evidence of the palaeovegetation associated with Protabrocoma, together with morphologic traits of the postcranium, suggests that this genus may have developed climbing adaptations in at least partially forested environments. This locomotor strategy for substrate use was probably present in the most recent common ancestor of extant species.