The American interchange of land mammals reached its acme during the late Blancan and
early Irvingtonian in North America and during the Chapadmalalan and Uquian in South
America. It lasted about two million years and included taxa adapted to diverse habitats. It
was preceded in the early Hemphillian in North America and the Huayquerian in South
America by the interchange of a few heralding genera. The MacArthur-Wilson faunal
equilibrium hypothesis correctly predicts a marked increase in originations, number of …