The great diversity of the Paleogene hystricognath rodents from Santa Rosa (Peru)

ARNAL, MICHELLE; PÉREZ, MARÍA ENCARNACIÓN; TEJADA MEDINA, LUZ MARINA; CAMPBELL, KENNETH E.

Congreso; XII Congreso de la Asociación Paleontológica Argentina (Virtual); 2021

Hystricognath rodents arrived in South America from Africa at an unknown moment during the Paleogene. The most ancient assemblages of these South American hystricognaths (Caviomorpha) were studied intensively in recent years. One of these assemblages is the abundant and diverse caviomorph fauna from the locality of Santa Rosa, Peru. Their age was originally estimated as ?Eocene based on biostratigraphy and the evolutionary stage of the composite paleofauna. In this work, we report new caviomorph fossils from Santa Rosa and review the previously described rodents taking into account new dating analyses 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 represent one of the oldest and the most diverse of the known caviomorph paleofaunas from low latitudes of South America. In addition, the new dates and the caviomorph taxonomic similarities between Santa Rosa and other Paleogene assemblages of low-middle latitudes led us to propose an early Oligocene age for those rodents from the Alto Yurúa River in Brazil and a closer temporal relationship with the oldest Contamana levels. This new biochronologic scenario has deep implications in 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.