Caviomorpha are those hystricognath rodents endemic to the Neotropics. They are the most diverse group of rodents considering their morphological disparity and biology. Their evolutionary history goes back to the Eocene (ca. 40 Ma) and their excellent fossil record indicates that this fascinating clade occupied a wide range of niches. For this contribution, we considered those caviomorph rodents that inhabited the Argentinian Pampean region, limited to the provinces of Buenos Aires and La Pampa, from the Late Miocene to the Present. During the Late Miocene, caviomorphs underwent profound changes that led to the appearance of the most modern lineages (e.g. Octodontidae, Abrocomidae, Hydrochoerinae, Caviinae, Dolichotinae, Lagostomus). Later, during the Pliocene and Pleistocene, Pampean caviomorph assemblages experienced minor changes, and just by the Pleistocene/Holocene, modern taxonomic composition was already established. These changes seem to be related to environmental changes influenced by the aridization and cooling of the southern part of South America. Owing to its geographic position, the Pampean region acted as an ecotone between the Patagonian and Brazilian faunas, becoming an interesting object of study. In this contribution, we updated the systematic paleontology of the Argentinian Pampean caviomorphs. This revised systematic paleontology will contribute to a better understanding of the biostratigraphic scheme for this region, according to the new list of exclusive taxa for each Stage/Age. It will also provide a good base for studying the major pathways in the evolution of modern caviomorph lineages and the climatic changes in southern South America since the Late Miocene.
