Prehistoric Poo Linked Dinosaurs to Snails

One of the many reasons I love paleontology is that every now and then I stumble across a paper on some aspect of ancient life I had never considered before. There is much more to the science than descriptions of new species, and one of the studies that most recently caught my eye carried the title "Opportunistic exploitation of dinosaur dung: fossil snails in coprolites from the Upper Cretaceous Two Medicine Formation of Montana."

As reported in the 2009 study, paleontologists digging at a 76-million-year-old site within the well-known Two Medicine Formation have found more than 130 snail specimens closely associated with—and sometimes even within—the fossilized feces of herbivorous dinosaurs. Scientists had long recognized that the snails were present in the same deposits as the dinosaurs, indicating that they shared the same habitat, but no one had systematically documented interactions between the large vertebrates and the small gastropods. In fact, up to seven different snail taxa were found in close association with the dinosaur coprolites. Apparently dinosaur poo was a regularly-used resource by many species of snail.

The occurrence of snail fossils within the dinosaur dung was also used by the scientists behind the study to reconstruct what kinds of habitats the animals were living in. Since the most common snails on and within the coprolites were terrestrial snails, the authors of the study propose that the dinosaurs left their droppings on dry land before their feces were subsequently flooded (which would have filled in dung beetle burrows also seen in the coprolites). Although they noted that some of the snail shell fragments within the coprolites could have come from snails that were accidentally ingested while the dinosaurs were eating leaves and rotting wood, at least half of the snail fossils were intact and show no signs of being digested. This suggests that the snails made their way to the dino pats after they were deposited, with the dinosaur feces providing warm, wet, food-rich mini-environments that the snails could comfortably exploit.

CHIN, K., HARTMAN, J., & ROTH, B. (2009). Opportunistic exploitation of dinosaur dung: fossil snails in coprolites from the Upper Cretaceous Two Medicine Formation of Montana Lethaia, 42 (2), 185-198 DOI: 10.1111/j.1502-3931.2008.00131.x

Riley Black | | READ MORE

Riley Black is the author of The Last Days of the Dinosaurs and many other books. She is a science correspondent for Smithsonian magazine covering fossils and natural history, and she writes about the prehistoric past for a variety of publications.