xvi, 169 p. ： ill. (some col.) / This dissertation describes the postcranial functional morphology of Theropithecus brumpti , a fossil cercopithecoid primate from the Plio-Pleistocene of East Africa. Theropithecus is often used as an analogue for human evolution, but much of our understanding of its paleobiology is based on the grassland adapted Theropithecus oswaldi , masking potential morphological and ecological breadth within the genus and limiting its use as an ecological comparator. To better understand the evolutionary history and ecological breadth of the genus, an analysis of the woodland associated T. brumpti is presented. All available T. brumpti postcranial material is included, along with comparative data on T. oswaldi and a large extant sample. Skeletal elements were metrically described using 125 postcranial measurements believed to have functional relevance. Measurements were transformed into 46 ratios to reflect shape and the functional lengths over which muscles act and to reduce the effects of differences in scale among individuals and species. Contrary to previous findings, there is no evidence T. brumpti was arboreal; rather it is clearly a terrestrial papionin. While T. brumpti retains a degree of flexibility (at the shoulder, elbow, hip, knee and ankle), this is not exceptional when compared to other members of the genus, notablyT. oswaldi . Not only are traits similar in both species, but there is a wide range of variation and overlap in both. Features historically used to reconstructT. brumpti as more arboreal are interpreted here as part of a suite of traits that characterize early Theropithecus . This suite of traits may instead be adaptations to manual terrestrial foraging, in particular adaptations related to forest floor locomotion and gleaning, which may be primitive for Theropithecus and possibly for papionins. This interpretation of the paleobiology of T. burmpti compared to that of T. oswaldi offers a parallel with hominins. New fossil evidence suggests use of terrestrial substrates in more woodland habitats for late Miocene to early Pliocene hominins, in contrast to more open habitats associated with later hominins. Therefore, this dissertation develops a framework for understanding the woodland to grassland transition among large bodied primates including hominins. / Committee in charge: Stephen Frost， Chairperson； Frances White， Member； John Lukacs， Member； Samantha Hopkins， Outside Member