Bud feeding in the fossil record; a case study of leaf compressions from the Eocene Geiseltal fossil site, Germany

Many dicotyledonous plants employ folding of immature leaf surfaces into buds before developing into mature leaves. Bud folding in leaves is impacted by taxonomy and ecology, and fossil evidence provides insight into its evolution. Direct evidence of leaf-bud folding patterns is rare in the fossil record. Herein, we describe leaf compressions from the middle Eocene (47.8-37.71 Ma) Geiseltal lignite deposits in Germany, which exhibit feeding damage consisting of files of holes across the leaf (damage types DT06 and DT425). We compare the damage on these leaves to various models of bud-feeding, including digital and paper origami, and artificial damage to living leaf buds, to more accurately interpret the fossils. One of the specimens exhibits a complex damage pattern, which can be roughly assigned to seven lines of holes across the leaf. Models based on this fossil leaf indicate that the pattern of damage is consistent with an insect feeding on a leaf bud that was folded in a semi-corrugated pattern, creating the observed damage after bud burst (DT06). The two other fossil leaves exhibit a simpler pattern of bilaterally symmetrical damage. This likely resulted from an insect feeding on these leaves while they were folded in half, as a bilaterally folded bud, or a mature leaf folded in half at night or in response to herbivory (DT425). The patterns observed in these fossil leaves may confirm ecologies and life histories that are not otherwise directly recorded. Moreover, the models presented here contribute to recognizing bud-feeding traces in the fossil record.