A reassessment of the taxonomic and phylogenetic affinities of the fossil catarrhines from fort Ternan, Kenya

This paper presents a reassessment of the taxonomic and phylogenetic affinities of the fossil catarrhine primates from the important middle Miocene site of Fort Ternan in Kenya. Although the sample of specimens is rather small, the material can be attributed to at least five different species, identified here as Kenyapithecus wickeri, Proconsul sp., a large species of oreopithecid, Simiolus sp., and a small species of catarrhine of indeterminate status. Kenyapithecus wickeri probably represents a conservative sister-taxon of the extant large hominoids. It is more derived than "Sivapithecus" africanus from Maboko Island, from which it can be distinguished at the generic level. A small species of catarrhine from Fort Ternan can be attributed to Simiolus. It is probably a different species from Simiolus enjiessi from the early Miocene of East Africa, but additional material is needed to confirm its taxonomic distinctiveness. The occurrence of at least five species of catarrhine primates at Fort Ternan confirms that species diversity levels were as high during the middle Miocene as they had been during the early Miocene. However, the overall taxonomic and ecological composition of the middle Miocene catarrhine community was quite different, evidently due to a significant change in the local ecological setting. Taxonomic differences between the catarrhine faunas at Fort Ternan and Maboko Island can probably be explained as a consequence of a chronological separation between the two sites, and, to a lesser degree, to paleoecological differences.