Coprolites

Coprolites are fossilized feces, preserved in sedimentary rocks, that provide direct evidence of the diet and gut processes of ancient organisms. They form when fecal material is rapidly buried and subsequently mineralized, often by replacement with calcium phosphate, silica, or carbonate, or when it becomes encased in a concretion or matrix rich in mineralizing fluids. Coprolites can range from small pellets to large, elongated masses and are commonly found in fossil-bearing stratigraphic units such as ancient river deposits, lakebeds, or marine sediments.

The internal contents of coprolites—including bone fragments, scales, teeth, seeds, shells, wood fragments, pollen, or other undigested food—are diagnostic of the producer’s trophic level and sometimes of its taxonomy. However, linking a coprolite to a specific species can be difficult unless there is accompanying trackways, body fossils, or distinctive contents. As a result, many coprolites are attributed to broad groups (for example, marine fish, reptiles, or mammals) rather than to a single animal. Dating coprolites typically relies on the age of the surrounding rock, though some phosphate-hosted specimens yield age estimates from uranium-series dating. Coprolites have been valuable in reconstructing past ecosystems, food webs, and paleodiets, and they often illuminate feeding strategies, digestive adaptations, and the prevalence of certain foods (such as bone in theropod dinosaur coprolites or plant material in herbivorous forms).