Coprolites: The Joys of Dinosaur Poop

When I used to teach elementary school children about dinosaurs, I would pass around a fossil and ask them what part of the dinosaur they thought it was. After some wild guesses, I would tell them it was a coprolite. When no one could identify it, I explained that it was dinosaur feces. Still no response, until I explained that it was fossil of dinosaur poop. There would always be a lot of ewws and ughs and even requests to go wash hands.

Ancient feces did sometimes become fossils, and scientists have named these fossils coprolites, literally "poop-stones." Such feces fossils provide information about what ancient animals ate (and that tells us what plants and animals shared their environment). Dinosaurs are not the only prehistoric animals to leave us such fossils, but they are certainly the most interesting.

Coprolites are rare, compared to skeleton fossils, because soft material such as feces (or poop, in kid-speak) is not as likely to survive. Strangely, the first descriptions of coprolite, by William Buckland, are older than descriptions of dinosaur bone fossils. Although William Buckland drew his conclusions on the visual similarity of the fossils to modern feces, most coprolite looks very different. Sometimes, coprolites have been identified by the appearance of dung beetle tracks in the fossil.

The appearance of coprolites is as different as the animals that produced the original feces, showing differences in diet and environment. Coprolites appear in quite a variety of shapes, some of which make us wonder if dinosaurs suffered from hemorrhoids. Coprolites also come in quite a range of colors, which do not reflect the original colors of the poop, but instead, they indicate the mineral content of the material in which the fossils were preserved.

One of the trickiest facts to figure out about coprolites is which animal left the fossil for us. We can tell whether the dinosaur or other animal ate meat or plants, but unless a coprolite is found in the body of an animal, we cannot be sure of its source. Still, coprolites found near bones of a dinosaur might not be a product of that animal.