Locomotor evolution of Mesopithecus (Primates: Colobinae) from Greece: evidence from selected astragalar characters

This paper reports our investigations into functional aspects of the astragalus of four samples of the genus Mesopithecus from Greece. More particularly, it aims to infer substrate preferences of M. delsoni/pentelicus from the Middle Turolian site of Perivolaki (central Greece), M. pentelicus from the late Middle Turolian site of Pikermi (southern Greece), and M. cf. pentelicus and M. cf. monspessulanus from the Late Turolian site of Dytiko (northern Greece). For these purposes, selected astragalar functional features, such as trochlea wedging, proximal facet curvature, and head rotation were expressed as linear measurements on both fossil and selected extant colobines. The size-adjusted measurements were used for univariate comparisons as well as a multivariate principal components analysis. Both approaches revealed that the selected characters were able to discriminate between extant arboreal and semiterrestrial colobines, but all fossil forms presented mosaic morphology. Thus, the oldest representative, M. delsoni/pentelicus was reconstructed as mainly semiterrestrial. On the other hand, the astragalus of M. pentelicus appeared to reflect semiterrestrial habits with a moderate adaptation to arboreality. Similar habitus reconstruction was allocated to the more recent M. cf. pentelicus, whereas the sympatric and synchronous M. cf. monspessulanus showed semiterrestrial adaptations with a slight preference of terrestrial substrates. The results mainly conform to paleoenvironmental reconstructions of the fossiliferous localities and denote that Mesopithecus was mainly a semiterrestrial radiation throughout its evolutionary history, with differential rates of use between arboreal and terrestrial substrates. These adaptations could have promoted the dispersal of the genus throughout Eurasia during the latest Miocene and Early Pliocene.