The oldest record of external foliage feeding and the expansion of insect folivory on land

Abstract

We describe three specimens from a Late Mississippian (earliest Serpukhovian) pteridosperm (seed fern) Triphyllopteris austrina (Etheridge Jr.) Morris, of probable lyginopterid affinities, which originates from the Sugar Loaf Creek locality of the Sydney Basin, Australia. These specimens provide six examples of folivory assigned to the ichnotaxon Phagophytichnus ekowskii van Amerom 1966. This damage is the earliest example of folivory in the terrestrial fossil record and probably was produced by a "protorthopteroid" or other basal orthopteroid insect, although a more remote possibility is that the culprit was a diplopod. Three important consequences result from this discovery. First, leaves originated 76 million years (m.y.) before the first indication of their folivory. Second, a temporal lag of 6 m.y. is present between the occurrence of T. austrina folivory and the subsequent earliest appearance of herbivorous insect clades in the body-fossil record that could have caused the damage. Third, once the hurdle of folivory was breached, the overwhelming preference of Paleozoic insect folivores was on a taxonomically diverse, paraphyletic spectrum of pteridosperm hosts.