Excavation of the late Miocene primate fauna in Nakali, Kenya and its evolutionary implications

通过对Nakali组（980 - 990万年前）的古生物和地质调查，记录了该时期的哺乳动物群落，包括几种灵长类动物，揭示了该时期的古环境及其生态适应性。哺乳动物分类有6目30余种。数量最多的灵长类动物是Microcolobus sp.这个物种是一种小型的colobine，其大小与现存最小的colobine相当，并适应在森林环境中生活。草食性哺乳动物牙釉质化石的稳定碳同位素研究也支持了森林（C3）古环境的假设。研究还揭示了东非的C4环境扩张是在Nakali组时代之后进行的。地质调查显示，Nakali组向南扩展的范围比我们先前预期的要大。

We conducted paleontological and geological survey of the Nakali Formation (9.8-9.9 million years ago), documented the mammal community of this age including several primate species, and revealed its paleoenvironment and their ecological adaptations. Mammalian taxa counted 6 orders and more than 30 species. The most abundant primate is Microcolobus sp. This species is a small colobine that is comparable to the smallest extant colobine in size and was adapted for living in forested environment. The presumed forested (C3) paleoenvironment was also supported from stable carbon isotope study of fossilized enamel of herbivorous mammals. This study also revealed that C4 environmental expansion progressed after the age of the Nakali Formation in East Africa. The geological survey revealed that the Nakali Formation expands southward more widely that our previous expectation.