AN EARLY MIOCENE ANTHROPOID SKULL FROM THE CHILEAN ANDES

PARTLY because of their poor fossil record, the relationships of neotr opical platyrrhine monkeys to other groups of primates and to each oth er remain perhaps the most poorly known for any major primate clade(1) . Here we report the discovery of a complete platyrrhine skull from th e Andes of central Chile, by far the best preserved Tertiary primate c ranium from South America. This find, coupled with recent phylogenetic analyses of higher groups of anthropoid primates(2-4), has the potent ial to revise substantially our understanding of platyrrhine interrela tionships, indicating, among other points, significant modification to reconstruction of the ancestral platyrrhine morphotype and a likely A frican origin for New World monkeys. A Ar-40/Ar-39 radioisotopic date directly associated with the skull indicates an Early Miocene age(5), marking the first report of South American mammals of this age from ou tside Argentine Patagonia. Finally, this discovery demonstrates the en ormous potential of vastly distributed, but virtually untapped, Andean volcaniclastic deposits to yield further insights into the origin and diversification of South American primates.