Damage caused by insects is common in fossil leaves. This study examined the question of whether the incidence of insect leaf damage increased during an approximately 50 million year span of angiosperm history, both overall and within a single clade, the Platanaceae. Platanaceae were chosen as the sample lineage because their leaves are readily identifiable and the group has a well documented first appearance approximately 5 to 10 Myr prior to the Cenomanian. A series of five fossil floras were examined: the Dakota Flora of Kansas (~98 Ma; Cenomanian), the Eagle Flora of northwestern Wyoming (~81 Ma; Campanian), the Hell Creek Flora of southwest North Dakota (~65-67 Ma; Maastrichtian), the Fort Union Flora of east central Montana (~63 Ma; Torrejonian) and the Kishenehn Flora from western Montana (~50 Ma; Eocene). Eight different categories of insect leaf damage were identified and tracked in these floras. Overall incidence of angiosperm leaf damage increases sharply from a mean value of 12.3 occurrences per 50 leaves (12.3/50) in the Dakota Flora to values above 33/50 in the four later floras. Incidence of all categories of leaf damage to the Platanaceae in the Dakota Flora is considerably less (8.9/50) than in the non-Platanaceae (25.6/50). Thereafter, the difference in the leaf damage index for the Platanaceae does not differ significantly from the damage index for other angiosperms, with the possible exception of the Hell Creek Flora where the platanaceous damage index is 31.6/50 as opposed to 37.3/50 for non-Platanaceae. However, throughout the interval from the Cenomanian to the Eocene, the Platanaceae remained consistently less susceptible to margin feeding than the non-platanaceous angiosperms. Between the Cenomanian and the Campanian two new types of leaf damage appear: window feeding and skeletonization. At first, these damage types occur less frequently in Platanaceae but this differential is erased by the Maastrichtian. Among leaf mines, an Ectoedemia-like (Nepticulidae) mine first appears in the Maastrichtian Hell Creek Flora, and mines of Paraclemensia (Incurvariidae) appear between the Hell Creek Flora and the Fort Union Formation.

Key words: Eocene, insect leaf damage, Late Cretaceous, Paleocene, Platanaceae