Earliest colobine skeletons from Nakali, Kenya
Article first published online: 27 MAY 2010
Copyright © 2010 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 143, Issue 3, pages 365–382, November 2010
How to Cite
Nakatsukasa, M., Mbua, E., Sawada, Y., Sakai, T., Nakaya, H., Yano, W. and Kunimatsu, Y. (2010), Earliest colobine skeletons from Nakali, Kenya. Am. J. Phys. Anthropol., 143: 365–382. doi: 10.1002/ajpa.21327
- Issue published online: 27 MAY 2010
- Article first published online: 27 MAY 2010
- Manuscript Received: 3 NOV 2010
- Manuscript Accepted: 29 MAR 2010
- Japan Society for Promotion of Science
- MEXT, Japan. Grant Numbers: 18255006, 19207019, 19107007
- Old World monkeys;
Old World monkeys represent one of the most successful adaptive radiations of modern primates, but a sparse fossil record has limited our knowledge about the early evolution of this clade. We report the discovery of two partial skeletons of an early colobine monkey (Microcolobus) from the Nakali Formation (9.8–9.9 Ma) in Kenya that share postcranial synapomorphies with extant colobines in relation to arboreality such as mediolaterally wide distal humeral joint, globular humeral capitulum, distinctly angled zona conoidea, reduced medial trochlear keel, long medial epicondyle with weak retroflexion, narrow and tall olecranon, posteriorly dislocated fovea on the radial head, low projection of the femoral greater trochanter, wide talar head with a greater rotation, and proximodistally short cuboid and ectocuneiform. Microcolobus in Nakali clearly differs from the stem cercopithecoid Victoriapithecus regarding these features, as Victoriapithecus is postcranially similar to extant small-sized terrestrial cercopithecines. However, degeneration of the thumb, a hallmark of modern colobines, is not observed, suggesting that this was a late event in colobine evolution. This discovery contradicts the prevailing hypothesis that the forest invasion by cercopithecids first occurred in the Plio-Pleistocene, and shows that this event occurred by the late Miocene at a time when ape diversity declined. Am J Phys Anthropol 143:365-382, 2010. © 2010 Wiley-Liss, Inc.