Data from: An Early Oligocene age for the oldest known monkeys and rodents of South America

The Santa Rosa fossil locality in eastern Perú produced the first
Paleogene vertebrate fauna from the Amazon Basin, including the oldest
known monkeys from South America. This diverse paleofauna was originally
assigned an Eocene age, based largely on the stage of evolution of the
site’s caviomorph rodents and marsupials. Here we present new detrital
zircon dates that indicate that the maximum composite age of Santa Rosa is
29.6±0.8 Ma (Lower Oligocene), although several zircons from Santa Rosa
date to the Upper Oligocene. The first appearance datum for Caviomorpha in
South America is purported to be the CTA-27 site in the Contamana region
of Perú, which is hypothesized to be ~41 Ma (Middle Eocene) in age.
However, the presence of the same caviomorph species and/or genera at both
CTA-27 and at Santa Rosa is now difficult to reconcile with a >11
Myr age difference. To further test the Middle Eocene age estimate for
CTA-27, we ran multiple Bayesian tip-dating analyses of Caviomorpha,
treating the ages of all Paleogene species from Perú as unknown. These
analyses produced mean age estimates for Santa Rosa that overlap with the
maximum 29.6±0.8 Ma composite date provided by detrital zircons, but
predict that CTA-27 is much younger than currently thought (~31-30 Ma). We
conclude that the ~41 Ma age proposed for CTA-27 is incorrect and that
there are currently no compelling Eocene records of either rodents or
primates in the known fossil record of South America.