Provisional classifications and key to living species of macaques (primates: Macaca)

19 recognized species of macaques (Macaca) are allocated to four species groups (fascicularis group, silenus-sylvanus group, sinica group, arctoides group) based primarily on structure of male external genitalia. Geographic ranges of all four species groups are partly sympatric; ranges of species within each group apparently are allopatric. Distribution patterns suggest that the silenus-sylvanus group probably dispersed earliest, the sinica group next, and the fascicularis group most recently; successively more recent dispersals probably contributed to reduction and disjunction of ranges of species groups that dispersed earlier. An artificial key to external characters of recognized species is presented. Deficiencies are noted in Hill's recently published taxonomic traeatment of macaques; these criticisms concern Hill's classification, key, nomenclature and range maps.