The biogeographic affinities of the Florissant flora are in need of reevaluation. We give a critical review, based on megafossil and pollen records representing genera whose affinities we accept as well founded. The Florissant assemblage includes taxa of diverse modern geographic distribution. The flora is composed mainly of Laurasian elements, some of which are now confined to Asia (Ailanthus, Dipteronia, Eucommia, Platycarya, Pteroceltis) and a wide number co-occurring in the eastern United States and Asia. Others are now confined to western North America (Sequoia, Cercocarpus, Sarcobatus) and many occur in...