Explanation

Not every scar or discoloration on a living leaf is caused by insects feeding. Marks can result from physical damage, such as leaves rubbing against other objects, or from the plant’s own stress responses, including inflammation caused by fungal or viral infections. In the case of plant fossils, there are even more possibilities to consider, including damage that occurred during fossilization or later during collection and preparation.

One important clue is pattern. Insect feeding and egg-laying are behaviors that tend to be repeated, so true traces often show similar-sized marks in similar positions—either within a single leaf or across multiple leaves from the same site. Random tearing or abrasion is less likely to produce such consistent, repeated shapes.

(1) Feeding and oviposition traces may have formed while the plant was alive, or after the leaf had detached from the plant (that is, after the tissue had died).

(2) During burial and fossilization, leaves can be marked by organisms moving through sediment, or they may be scratched and torn while being transported with other debris. Patterns that resemble feeding damage can also arise from mineral growth or from the way the fossil was preserved.

(3) Additional marks may have been created when the fossil was split, trimmed, or otherwise prepared, sometimes damaging or peeling the surface.

For these reasons, the study of feeding-trace fossils requires looking at both the marks themselves and their context: the circumstances in which the fossil was found (including the surrounding rock and sediment) and the way it has been preserved. Researchers ask whether there is evidence the damage was made while the plant was alive, and they consider alternative explanations before concluding that a mark is a feeding trace—much like detective work.

This database mainly focuses on traces that were made while the plant was still alive, although some marks may have formed after the leaf had fallen and died.