Skeletal and dental morphology supports diphyletic origin of baboons and mandrills

Numerous biomolecular studies from the past 20 years have indicated that the large African monkeys Papio, Theropithecus, and Mandrillus have a diphyletic relationship with different species groups of mangabeys. According to the results of these studies, mandrills and drills (Mandrillus) are most closely related to the torquatus-galeritus group of mangabeys placed in the genus Cercocebus, whereas baboons (Papio) and geladas (Theropithecus) are most closely related to the albigena-aterrimus mangabeys, now commonly placed in the genus Lophocebus. However, there has been very little morphological evidence linking mandrills on the one hand and baboons and geladas on the other with different groups of mangabeys. In a study of mangabey locomotion and skeletal anatomy, we have identified features of the postcranial skeleton and the dentition that support the molecular phylogeny and clearly link mandrills with Cercocebus and Papio with Lophocebus. Moreover, the features linking Cercocebus and Mandrillus accord with ecological studies of these species indicating that these two genera are a cryptic clade characterized by unique adaptations for gleaning insects, hard nuts, and seeds from the forest floor.