The Cretaceous Diversification of Angiosperms: Perspectives from Mesofossils

Abstract

The plant fossil record during the Cretaceous documents a major transition in the dominant group of terrestrial autotrophs, as plant communities from the earlier Mesozoic were transformed by the appearance and rapid diversification of angiosperms. This transformation began in the Early Cretaceous, continued through the Late Cretaceous, and led ultimately to the dominance of angiosperm in most terrestrial ecosystems today, which had profound consequences for the other organisms inhibiting terrestrial ecosystems and perhaps the planet as a whole. Our understanding of angiosperm diversification has been greatly improved over the past 50 years by integrated studies of fossil assemblages containing angiosperm pollen and leaves, but especially by new information from mesofossil floras that have provided previously unanticipated detail on floral form in Cretaceous angiosperms and have allowed the recognition of key dispersed pollen types in situ . Information from fossil flowers has greatly facilitated meaningful comparisons with living plants and integration with phylogenetic analyses of extant angiosperms based on DNA evidence. The combined insights from these discoveries provide a broadly consistent and coherent picture of angiosperm evolution through the Cretaceous, which comprises more than half of their entire evolutionary history.