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 detrital zircon dates that indicate that the maximum composite age of Santa Rosa is 29.6 ± 0.08 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-My 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 closely approximate the maximum 29.6 ± 0.08 Ma composite date provided by detrital zircons, but predict that CTA-27 is much younger than currently thought (∼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.

Primate diversity in the early Miocene Pinturas Formation, southern Patagonia, Argentina.

We report ten new dental specimens of primates from the early Miocene Pinturas Formation, Patagonia, Argentina. The new material includes: a left lower canine and a left upper canine whose affinities remain to be determined; a mandibular fragment preserving part of the symphysis; and right p3-4, practically indistinguishable from Soriacebus adrianae; and a lower molar, probably m2, attributable to S. ameghinorum. A lower molar, probably m3, a P4, and an upper molar resemble Carlocebus carmenensis. Three additional specimens, too damaged for an accurate taxonomic assignment, are tentatively assigned to S. ameghinorum. The specimens here described can be assigned to taxa already known from the Pinturas Formation (S. ameghinorum, S. adrianae, and C. carmenensis) and provide new morphological information.

A parapithecid stem anthropoid of African origin in the Paleogene of South America.

Phylogenetic evidence suggests that platyrrhine (or New World) monkeys and caviomorph rodents of the Western Hemisphere derive from source groups from the Eocene of Afro-Arabia, a landmass that was ~1500 to 2000 kilometers east of South America during the late Paleogene. Here, we report evidence for a third mammalian lineage of African origin in the Paleogene of South America-a newly discovered genus and species of parapithecid anthropoid primate from Santa Rosa in Amazonian Perú. Bayesian clock-based phylogenetic analysis nests this genus (Ucayalipithecus) deep within the otherwise Afro-Arabian clade Parapithecoidea and indicates that transatlantic rafting of the lineage leading to Ucayalipithecus likely took place between ~35 and ~32 million years ago, a dispersal window that includes the major worldwide drop in sea level that occurred near the Eocene-Oligocene boundary.

Diet of the northern bearded saki (Chiropotes satanas chiropotes): A neotropical seed predator.

Data on the diet of Chiropotes satanas chiropotes, the northern bearded saki, has been collected during several years of primate field observations in the Raleighvallen-Voltzberg Reserve in Suriname. This species feeds predominantly on immature seeds and ripe fruit, mainly the former. Chiropotes is especially fond of the members of the Brazil nut family, Lecythidaceae, and other species with exceptionally hard or tough seed pods. Concomitantly, Chiropotes shows striking dental and gnathic adaptations that facilitate opening and ingesting these well-protected food items. Seed predation in the Old World colobine, Colobus satanas, has been discussed primarily as a strategy for survival in forests characterized by leaves with low nutrient content and high toxicity; however, it now appears that arboreal seed predation is a relatively widespread primate dietary strategy found among higher primate species in a variety of forest types on three continents. It is yet another way of "making a living" in a tropical rain forest.