The high taxonomic diversity of the Palaeogene hystricognath rodents (Caviomorpha) from Santa Rosa (Peru, South America) framed within a new geochronological context

ARNAL M.; PÉREZ M. E.; TEJADA MEDINA L. M.; CAMPBELL KENNETH

Congreso; Congreso de la Asociación Paleontológica Argentina; 2021

Hystricognath rodents arrived in South America from Africa at an unknown moment during the Paleogene. The most ancientassemblages of these South American hystricognaths (Caviomorpha) were studied intensively in recent years. One of theseassemblages is the abundant and diverse caviomorph fauna from the locality of Santa Rosa, Peru. Their age was originallyestimated as ?Eocene based on biostratigraphy and the evolutionary stage of the composite paleofauna. In this work, wereport new caviomorph fossils from Santa Rosa and review the previously described rodents taking into account new datinganalyses for this locality and updated knowledge of other Paleogene caviomorph assemblages. From the systematic study,we identified at least 18 genera and 22 species, including three new taxa. All taxa are brachydont, with quadrangular teeth,cusps generally visible, and crests tapering toward their apices. Results demonstrate that the Santa Rosa rodents representone of the oldest and the most diverse of the known caviomorph paleofaunas from low latitudes of South America. Inaddition, the new dates and the caviomorph taxonomic similarities between Santa Rosa and other Paleogene assemblagesof low-middle latitudes led us to propose an early Oligocene age for those rodents from the Alto yurúa River in Brazil anda closer temporal relationship with the oldest Contamana levels. This new biochronologic scenario has deep implicationsin the date of arrival of rodents into South America and in its early evolution, with a possible younger entrance (late Eocene?)of one or perhaps several waves of incoming African rodents.