Paleontology and Primate Evolution in the Late Oligocene of Kenya

包括旧大陆猴、猿和人类在内的灵长类动物化石记录的一个巨大空白是在非洲跨越了大约3000万到2000万年前的时间间隔。现在，肯尼亚西北部的两个晚渐新世遗址（大约24- 2700万年前）填补了这一空白，这两个遗址在2007年6月的初步田野调查中都发现了新的灵长类动物化石。目前的研究旨在从新的研究区域寻找更多代表更完整骨骼遗骸的灵长类动物化石，将灵长类动物纳入一个坚实的地质时代和古环境框架，并对其进行系统发育和古生物学分析。将在洛外和罗索德地区建立野外营地，并与包括学生在内的人类学家、古生物学家、地质学家等多学科人员一起进行研究，以回收灵长类动物化石、其他哺乳动物、爬行动物、鸟类化石、对古环境有重要意义的植物化石以及用于放射性、古地磁、地质同位素研究的岩石样本。总之，这些数据的分析将记录肯尼亚晚渐新世灵长类动物进化和古环境的模式。这项工作将与现有的早渐新世重要的基础卡塔鼻类和早中新世猿的大辐射的知识相结合，以便更好地理解从原始的早期卡塔鼻类到最早的大型类人猿的进化过渡。我们将讨论几个理论上重要的问题。一些问题围绕着晚渐新世卡塔林的分类学评估：在这个时期是否存在真正的人科动物（只包含猿类和人类的类人猿的成员），或者是类人猿灵长目化石的前身，或者是真正的人科动物的侧缘？正如最新的分子钟所预测的那样，旧大陆猴子和猿之间的进化分裂在这个时候发生了吗？其他重要的理论问题围绕着这些早期类人猿灵长类动物的适应，以及它们获得类人猿特征的顺序，例如骨骼适应其特有的攀爬运动，牙齿适应果食性饮食，以及与脑容量增加相关的颅骨适应。晚渐新世是非洲这个以前的岛屿大陆开始与北方大陆对接的时期，这一地理事件是否与非洲的气候变化、环境或生态的变化或动物群落的变化有关，这在理论上引起了相当大的兴趣。肯尼亚学生和博物馆工作人员将参与这个项目，许多关键的分析和实验室程序将与肯尼亚同事一起进行，为肯尼亚古生物学家提供新的机会和培训。

One of the great gaps in the fossil record of the primate group containing Old World monkeys, apes and humans (catarrhines) has been the one spanning the interval from about 30 to 20 million years ago in Africa. This gap has now been filled by two sites of Late Oligocene age (approximately 24-27 million years old) in northwestern Kenya, both of which yielded new primate fossils during preliminary fieldwork in June, 2007. The current research is designed to find more primate fossils representing more complete skeletal remains from the new research areas, to put the primates into a solid framework of geological age and paleoenvironment, and to conduct phylogenetic and paleobiological analyses of them. Field camps will be established at the sites of Nakwai and Losodok, and research will be conducted with an interdisciplinary crew of anthropologists, paleontologists, geologists, including students, to recover primate fossils, other mammals, reptiles and birds, fossils of paleoenvironentally important plants, and rock samples for radiometric, paleomagnetic, and geo-isotopic studies. Together, analyses of these data will document patterns of primate evolution and paleoenvironment during the Late Oligocene of Kenya. This work will be integrated into existing knowledge of the important basal catarrhines of the early Oligocene and the great radiation of apes in the early Miocene, in order to better understand the evolutionary transition from primitive, early catarrhines to the earliest large-bodied apes of the superfamily Hominoidea. Several issues of theoretical importance will be addressed. Some issues center around taxonomic assessments of Late Oligocene catarrhines: were true hominoids (members of the group containing only apes and humans) present at this time, or are the fossil ape-like primates precursors, or lateral relatives, of true hominoids? Had the evolutionary split between Old World monkeys and apes occurred by this time, as predicted by the latest molecular clocks? Other issues of theoretical importance center around the adaptations of these early ape-like primates, and the sequence in which they acquired ape-like traits, such as skeletal adaptations for their characteristic climbing movements, dental adaptations for frugivorous diets, and cranial adaptations associated with increasing brain size. The Late Oligocene is the period in which Africa, previously an island continent, was beginning to dock with the northern continents, and there is considerable theoretical interest in whether this geographic event was associated with African climatic change, shifts in environment or ecology, or changes in animal communities. Kenyan students and museum staff will be participate in this project, and many of the key analyses and laboratory procedures will be conducted with Kenyan colleagues, providing new opportunities and training for Kenyan paleontologists.