The terminal thumb phalanx of Orrorin tugenensis (Upper Miocene of Kenya)

The lion's share of articles dealing with the thumb anatomy of Plio-Pleistocene hominids has focussed on the capacity to manipulate and manufacture tools, and has largely neglected the locomotor aspects. However, in these hominids, the forelimb was still employed in locomotion. Certain of the anatomical characters classically associated with manipulation and/or fabrication of tools are already present in the Late Miocene species Orrorin tugenensis as shown by the terminal thumb phalanx BAR 1901'01. This specimen reveals crucial information suggesting that thumb morphology is not exclusively related to such tool using and manufacturing activities but reflects in a frequently bipedal creature a deeper adaptation concerning the precision grip essential for climbing and balancing, different from that of apes. (c) 2006 Elsevier SAS. Tous droits reserves.