ANGIOSPERMS FROM THE EARLY CRETACEOUS OF WYOMING

The classic sequences documenting the paleoecology and early radiation of angiosperms are from the Potomac Group of eastern North America. In spite of abundant outcrop and stratigraphic context, surprisingly little is known of the timing or ecological context of angiosperm radiation in western North America. Recent field work in the Cloverly Formation (Aptian-Albian) of northern Wyoming has revealed extensive deposits bearing plant megafossils at several levels. The time of deposition of the Cloverly is thought to correspond to the first major increase in eudicot diversity, and their spread from successional and disturbed habitats to a wider range of environments. Fourteen fossil plant sites identified from throughout the Cloverly Formation during the summer of 2010 should provide fresh evidence on the diversification and ecological spread of angiosperms. Sites near the base of the Cloverly contained only ferns and gymnosperms; sites near the top of the formation contained angiosperm leaves, which may be among the oldest records of the group in Western North America.