FOSSIL LEAVES REVEAL THE DIVERSIFICATION AND SPREAD OF FLOWERING PLANTS IN THE CLOVERLY FORMATION (CRETACEOUS, WESTERN INTERIOR, USA) (Invited Presentation)

The Lower Cretaceous Cloverly Formation (Fm.) in Wyoming is well known for its dinosaur fossils and more recently for its diverse microfauna; however, the plants that supported these Early Cretaceous communities are poorly understood. New field collections of fossil leaves from 31 sites made over the last five years demonstrate that plant macrofossils are common in the Cloverly Formation. Plant fossil collections from the lower part of the Cloverly Fm. near Ten Sleep, WY, include ferns, gymnosperms, and horsetails, but lack evidence of angiosperms. By contrast, collections from the uppermost beds (the Greybull interval) regularly include angiosperm fossils, but many are conifer or fern-dominated. These results, together with recently revised age estimates, indicate that by the late Albian angiosperms were diverse and widespread, occurring in a variety of fluvial subenviroments. Most angiosperm species were generally rare, but some were locally abundant in near-channel habitats. Leaf size and architectural features indicate that the angiosperm component was mostly herbaceous to shrubby, and comprises primarily eudicot angiosperms rather than magnoliids or monocots.