Emiliano Bruner, of the Paleoneurobiology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has just published an article in the American Journal of Primatology, which analyzes the peculiar cranial structure and variability of the best-known species of South American howler monkey, Alouatta seniculus, using multivariate statistics and geometric models in three dimensions.