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

我们对纳卡里组（980 - 990万年前）进行了古生物学和地质调查，记录了该时代的哺乳动物群落，包括几种灵长类动物，并揭示了其古环境及其生态适应。哺乳动物有6目30余种。最丰富的灵长类是Microcolobus sp.这个物种是一种小型的colobine，与现存最小的colobine大小相当，并适应于生活在森林环境中。草食性哺乳动物牙釉质的稳定碳同位素研究也支持森林（C3）的古环境。这项研究还表明，C4环境扩张在东非Nakali组时代之后取得了进展。地质调查显示，Nakali组向南扩展的范围比我们先前的预期更广。

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.