The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Fossil forelimbs of Simiolus from Moruorot, Kenya

JAMES B. ROSSIE1, MERCEDES GUTIERREZ2 and EMILY GOBLE3.

1Department of Anthropology, SUNY Stony Brook, 2Department of Anatomy and Cell Biology, Tufts University, 3Human Origins Program, NMNH, Smithsonian Institution

Thursday 2:00-2:15, Broadway III/IV Add to calendar

The “small apes” of the African early Miocene are very poorly represented by postcranial material. Associated elements of these species are even rarer, consisting mainly of several partial limb bones of Dendropithecus from Rusinga Island. Previous collecting at the early Miocene site of Moruorot in Northwest Kenya produced a distal humerus and radial fragments from a small ape (Rose et al., 1992, J Hum Evol 22:171-237). Our ongoing excavations at Moruorot have recovered additional material apparently belonging to the same individual, including conjoining segments of the previously collected radius. To date, these include most of the left arm and forearm and portions of the right forelimb, including an exceptionally preserved almost complete right hand. Attribution of this material to the genus Simiolus is based on similarities to the few Simiolus elements known from Kalodirr, along with significant differences from Dendropithecus that our new fossils make evident.

This new material adds considerably to our understanding of the postcranial morphology of Simiolus, and reveals some diversity in positional behavior among the small non-cercopithecoid catarrhines of the early Miocene. Simiolus had more elongated forearms than Dendropithecus as well as relatively long metacarpals and phalanges, suggesting enhanced manual grasping and reaching/bridging abilities. However, Simiolus retained a proximally protruding (though short) ulnar olecranon process, as well as styloid-triquetral contact in the wrist. The discovery of fossil catarrhines possessing such trait combinations is our only means of discovering the pattern of mosaic evolution that lead to the crown hominoid postcranium.

This research is supported by National Geographic Society Waitt Grant W143-10.

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