The Earliest Remains of Grasses in the Fossil Record

Abstract

New fossils provide the earliest unequivocal evidence of grasses. Spikelets and inflorescence fragments with included pollen from the Paleocene/Eocene Wilcox Formation in western Tennessee have a suite of diagnostic characters that limits their affinities to Poaceae. Associated vegetative remains are also suggestive of grasses, but are not well enough preserved for an unequivocal identification. These fossils indicate a minimal time of origin for the family, are consistent with an Upper Cretaceous origin of Poaceae, and suggest that as in wind-pollinated Hamamelididae, wind pollination evolved in grasses or persisted in the grass lineage (if a wind-pollinated grass sister group is presumed) in dry tropical environments.