Early Cercopithecid Monkeys from the Tugen hills, Kenya

The modern Old World Monkeys (Superfamily Cercopithecoidea, Family Cercopithecidae) can be traced back into the late Miocene, but their origin and subsequent diversification is obscured by the scarcity of terrestrial fossil sites in Africa between15 and 6 Ma. Here, we document the presenceofcercopithecidsat12.5Mainthe Tugen Hills of Kenya. These fossils add 3 My to the known antiquity of crown Cercopithecidae. The two specimens represent oneorpossibly two species of early colobine, and their morphology suggests that they were less folivorous than their modern relatives.