Three-dimensional Morphology of the Sigmoid Notch of the Ulna in Kenyapithecus and Proconsul

The three-dimensional (3-D) morphology of the sigmoid notch was examined in Kenyapithecus, Proconsul, and several living anthropoids by using an automatic 3-D digitizer. It was revealed that Kenyapithecus and Proconsul exhibit a very similar morphology of the distal region of the sigmoid notch; including the absence of a median keel and a downward sloped coronoid process. In addition, the proximal region of the sigmoid notch is curved more acutely relative to the distal region in Proconsul. This morphological complex is unique and not found in the examined living primates. The benefits of 3-D morphometries are discussed.