ECOLOGICAL ASPECTS OF THE CRETACEOUS FLOWERING PLANT RADIATION

The first flowering plant fossils occur as rare, undiverse pollen grai ns in the Early Cretaceous (Valanginian-Hauterivian). Angiosperms dive rsified slowly during the Barremian-Aptian but rapidly during the Albi an-Cenomanian. By the end of the Cretaceous, at least half of the livi ng angiosperm orders were present, and angiosperms were greater than 7 0% of terrestrial plant species globally. The rapid diversification of the group, and its dominance in modem vegetation, has led to the idea that the Cretaceous radiation of angiosperms also represents their ri se to vegetational dominance. Paleoecological data cast a different li ght on the Cretaceous radiation of angiosperms. Analyses of sedimentar y environments indicate that angiosperms not only originated in unstab le habitats but remained centered there through most of the Cretaceous . Morphology of leaves, seeds, and wood is consistent with the status of most Cretaceous angiosperms as herbs to small trees with early succ essional strategy. The diversification of flowering plants in the Cret aceous represents the evolution of a highly speciose clade of weeds bu t not necessarily a major change in global vegetation.