The Hand of Cercopithecoides williamsi (Mammalia, Primates): Earliest Evidence for Thumb Reduction among Colobine Monkeys Frost, Stephen R. ; Gilbert, Christopher C. ; Pugh, Kelsey D. ; Guthrie, Emily H. ; Delson, Eric Abstract Publication: PLoS ONE Pub Date: May 2015 DOI: 10.1371/journal.pone.0125030 Bibcode: 2015PLoSO..1025030F