Primate differentiation in South America.

New World monkeys (or broadnosed monkeys) in South America form a distinctive group whose origin is still a mystery. The earliest known fossils, from Bolivia, are 26 million years old and have little help in resolving their origins. The Eocene neofossils from the Amazon region of Peru postponed this time record by 10 million years. They are more similar to extinct African primates than to existing or fossil broadnoses, suggesting that they are closely related to African species. These fossils also brought the first appearance of monkeys and guinea pig rodents (guinea pigs and similar groups) closer in South America, raising more questions about the origin of these distinctive groups in South America.