Morphoarchitectural variation in South African fossil cercopithecoid endocasts

International audienceDespite the abundance of well-preserved crania and natural endocasts in the South African Plio-Pleistocene cercopithecoid record, which provide direct information relevant to the evolution of theirendocranial characteristics, few studies have attempted to characterize patterns of external brainmorphology in this highly successful primate Superfamily. The availability of non-destructive penetratingradiation imaging systems, together with recently developed computer-based analytical tools, allow forhigh resolution virtual imaging and modeling of the endocranial casts and thus disclose new perspec-tives in comparative paleoneurology. Here, we use X-ray microtomographic-based 3D virtual imagingand quantitative analyses to investigate the endocranial organization of 14 cercopithecoid specimensfrom the South African sites of Makapansgat, Sterkfontein, Swartkrans, and Taung. We present the first detailed comparative description of the external neuroanatomies that characterize these Plio-Pleistoceneprimates. Along with reconstruction of endocranial volumes, we combine a semi-automatic techniquefor extracting the neocortical sulcal pattern together with a landmark-free surface deformation methodto investigate topographic differences in morphostructural organization. Besides providing andcomparing for the first time endocranial volume estimates of extinct Plio-Pleistocene South Africancercopithecoid taxa, we report additional information regarding the variation in the sulcal pattern ofTheropithecus oswaldi subspecies, and notably of the central sulcus, and the neuroanatomical condition ofthe colobine taxon Cercopithecoides williamsi, suggested to be similar for some aspects to the papioninpattern, and discuss potential phylogenetic and taxonomic implications. Further research in virtualpaleoneurology, applied to specimens from a wider geographic area, is needed to clarify the polarity,intensity, and timing of cortical surface evolution in cercopithecoid lineages