Coprolites as evidence for plant–animal interaction in Siluro–Devonian terrestrial ecosystems

Abstract

A FEW remarkable finds document the colonization of land by animals and plants in the mid-Palaeozoic1–3, but much rarer is unequivocal evidence for plant–animal interaction4,5. Here we announce the discovery of coprolites (fossil faeces) in Upper Silurian (412 Myr) and Lower Devonian (390 Myr) rocks from the Welsh Borderland that pre-date examples of similar composition in the Carboniferous by about 90 million years6,7. The majority consist predominantly of undigested land-plant spores with varying proportions of cuticles, tubes and less readily identifiable (presumably plant) material. Because coeval animal fossils of suitable size are carnivores8, direct evidence for the coprolite producers is lacking, but we speculate that they could have been spore eaters (and hence the earliest example of herbivory of higher plants) or detritivores similar to modern millipedes. In either case, they demonstrate the cycling of primary productivity in early terrestrial ecosystems.