摘要：The discovery of a rich and diverse vertebrate fauna in the Middle Miocene Muruyur Formation (ca. 14.5 Ma), Tugen Hills, Kenya, provides a rare view of the structure of the catarrhine fauna from this time period. Up to 2002, more than 140 catarrhine specimens have been collected from three sites (Kipsaraman, Keturo, and Cheparawa) represented by 199 teeth. At least six taxa are present, five ‘apes’ (hominoids sensu lato) and one cercopithecoid. Three of the taxa are new species. The Kipsaraman catarrhine fauna has some similarities to those of Maboko (ca. 15 Ma) and Fort Ternan (ca. 13.7 Ma), western Kenya, but it differs markedly from the Nachola (ca. 16 Ma) one, not only in the relative abundance of hominoids versus cercopithecoids, but also in the taxa represented. At Maboko and Kipsaraman, the most abundant catarrhine fossils are cercopithecoids, whereas these are rare at Nachola and unknown at Fort Ternan. At Kipsaraman, Maboko, and Fort Ternan, small ‘ape’ fossils are common, whereas they are absent from Nachola. Nyanzapithecus or a similar genus is present, but rare at all four sites. Kenyapithecus is present at Maboko, Fort Ternan, and Kipsaraman, but is absent from Nachola, its place being taken by Nacholapithecus which is abundant at the site. The catarrhine faunas from these Middle Miocene localities indicate that environmental conditions within East Africa were highly variable between 16 and 13.7 Ma.
