Numerous biomolecular studies from the past 20 years have indicated that th
e large African monkeys Papio, Theropithecus, and Mandrillus have a diphyle
tic relationship with different species groups of mangabeys. According to t
he results of these studies, mandrills and drills (Mandrillus) are most clo
sely related to the torquatus-galeritus group of mangabeys placed in the ge
nus Cercocebus, whereas baboons (Papio) and geladas (Theropithecus) are mos
t 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 o
ther with different groups of mangabeys. In a study of mangabey locomotion
and skeletal anatomy, we have identified features of the postcranial skelet
on 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 f
orest floor.