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Two catarrhine mandibles and five isolated teeth have been discovered from Early Miocene localities in Western Kenya. One mandible comes from the well-known locality of Songhor whereas the other is from a newly discovered locality, Lower Kapurtay, located near Songhor. The mandibles both can clearly be assigned to the species Rangwapithecus gordoni based on molar morphology, which is unique among Early Miocene catarrhines. The isolated specimens can be assigned to Rangwapithecus based on their similarities in morphology to the homologues preserved in the two mandibles. These specimens provide important new information about the dentognathic morphology of Rangwapithecus, which is described in detail. The mandible from Songhor (KNM-SO 22228) represents the first definitive female mandible of Rangwapithecus. The Lower Kapurtay mandible (KNM-KT 31234) appears to be male but is much smaller than another recently described male mandible of this species (KNM-SO 17500) and the type maxilla (KNM-SO 700). These specimens enable a reassessment of the attributions of all other mandibles and isolated lower teeth of Rangwapithecus, and we present a complete hypodigm of the mandibular and lower dental material for the species. Finally, we provide some additions to the diagnosis of Rangwapithecus gordoni based on previously unknown morphology. Am J Phys Anthropol 153:341–352, 2014. © 2013 Wiley Periodicals, Inc.

Two catarrhine mandibles and five isolated teeth have been discovered from Early Miocene localities in Western Kenya. One mandible comes from the well-known locality of Songhor whereas the other is from a newly discovered locality, Lower Kapurtay, located near Songhor. The mandibles both can clearly be assigned to the species Rangwapithecus gordoni based on molar morphology, which is unique among Early Miocene catarrhines. The isolated specimens can be assigned to Rangwapithecus based on their similarities in morphology to the homologues preserved in the two mandibles. These specimens provide important new information about the dentognathic morphology of Rangwapithecus, which is described in detail. The mandible from Songhor (KNM-SO 22228) represents the first definitive female mandible of Rangwapithecus. The Lower Kapurtay mandible (KNM-KT 31234) appears to be male but is much smaller than another recently described male mandible of this species (KNM-SO 17500) and the type maxilla (KNM-SO 700). These specimens enable a reassessment of the attributions of all other mandibles and isolated lower teeth of Rangwapithecus, and we present a complete hypodigm of the mandibular and lower dental material for the species. Finally, we provide some additions to the diagnosis of Rangwapithecus gordoni based on previously unknown morphology.