ABSTRACTFungal fruitbodies occurring on or in fossil leaves from a Miocene lake bed near Clarkia, Idaho, are documented and their ecological implications discussed. The epiphyllous mycoflora is limited to hyphopodiate mycelium and a plurivorous species of hemisphaerialean thyrothecium. Immersed fruit-bodies occur on most of the leaves examined. A diversity of host-specific forms are represented. None contain spores, suggesting either that the fruitbodies are immature or that the spores that they contained were hyaline and thin-walled, and thus unlikely to survive fossilization and extraction. These observations are consistent with a temperate, predominantly deciduous flora with early colonization of senescent leaves by pycnidial fungi.