Fossil cercopithecoid material from Ngeringerowa, Ngorora, and Nakali, dated at between 8.5 and 10.5 m.y., is described. The specimens are the only cercopithecoid remains dated between 15 and 6 m.y. from subSaharan Africa. The mandible of a small colobine from Ngeringerowa (similar in size to Colobus uerus) is assigned to a new genus and species, Microcolobus tugenensis. Unlike other colobine genera, the symphysis of Microcolobus lacks an inferior transverse torus. A colobine lower MI or 2 from Nakali is longer and narrower than molars of M. tugenensis, indicating that it may belong to a distinct taxon. A P4 from Ngorora cannot be assigned confidently to subfamily, due to its unique metaconid morphology. The relationship between the new genus and other Miocene monkeys is considered.

The past ten years have witnessed major changes in reconstructions of the history of Old World monkeys, most of them driven by new material of the Miocene monkey Victoriapithecus from Maboko Island, Kenya. Before the mid‐1980s, predictions about the morphological and ecological adaptations of the earliest cercopithecoids relied heavily on evidence from extant colobine and cercopithecine monkeys. It was argued that the earliest cercopithecoids were largely or at least partly folivorous, had short colobine‐like faces, and were arboreal. The only studies suggesting that some of these arguments were not true were based on limited knowledge of the anatomy of Victoriapithecus. The presence of semi‐terrestrial adaptations in middle Miocene monkeys hinted to some that early monkeys may not have been arboreal. Others attempted to cope with the discrepancy between neontological predictions and the fossil evidence by proposing that limb bones with stronger terrestrial adaptations within the Maboko sample were derived cercopithecine remains, while those with more arboreal features belonged in the subfamily Colobinae and should be regarded as primitive.

Our understanding of locomotor evolution in anthropoid primates has been limited to those taxa for which good postcranial fossil material and appropriate modern analogues are available. We report the results of an analysis of semicircular canal size variation in 16 fossil anthropoid species dating from the Late Eocene to the Late Miocene, and use these data to reconstruct evolutionary changes in locomotor adaptations in anthropoid primates over the last 35 Ma. Phylogenetically informed regression analyses of semicircular canal size reveal three important aspects of anthropoid locomotor evolution: (i) the earliest anthropoid primates engaged in relatively slow locomotor behaviours, suggesting that this was the basal anthropoid pattern; (ii) platyrrhines from the Miocene of South America were relatively agile compared with earlier anthropoids; and (iii) while the last common ancestor of cercopithecoids and hominoids likely was relatively slow like earlier stem catarrhines, the results suggest that the basal crown catarrhine may have been a relatively agile animal. The latter scenario would indicate that hominoids of the later Miocene secondarily derived their relatively slow locomotor repertoires.

Arboviruses spillover into humans either as a one-step jump from a reservoir host species into humans or as a two-step jump from the reservoir to an amplification host species and thence to humans. Little is known about arbovirus transmission dynamics in reservoir and amplification hosts. Here we elucidate the role of monkeys in the sylvatic, enzootic cycle of chikungunya virus (CHIKV) in the region around Kédougou, Senegal. Over 3 years, 737 monkeys were captured, aged using anthropometry and dentition, and tested for exposure to CHIKV by detection of neutralizing antibodies. Infant monkeys were positive for CHIKV even when the virus was not detected in a concurrent survey of mosquitoes and when population immunity was too high for monkeys alone to support continuous transmission. We conclude that monkeys in this region serve as amplification hosts of CHIKV. Additional efforts are needed to identify other hosts capable of supporting continuous circulation.