Prehistoric Poop Shows 'Vegetarian' Dinosaurs Actually Ate Shellfish

Scientists have discovered ancient dung that shows some dinosaurs previously believed to have been strict vegetarians often ate shellfish, as well as fungus and insects living in rotten logs. A new report says that the fossilized feces, called coprolites, contained crab and mollusk shells and rotted wood that date back to between 74 and 76 million years ago.

Lead researcher Karen Chin, a paleontologist at the University of Colorado, told NPR that the stool samples were discovered in the Grand Staircase-Escalante National Monument in Utah. She believes the prehistoric poop came from duck-billed dinosaurs called hadrosaurs. She adds that rotten wood is an unusual diet, but that the substance is high in fiber — a possible motive for a hungry dino. In eating the decomposing logs, "herbivores" were also swallowing the shellfish that lived inside it.

Crustaceans are a great source for protein and calcium, which is needed throughout the reproduction process. Chin tells Live Science that it could be possible female dinosaurs intentionally ate the shellfish in preparation for laying eggs.

Furthermore, researchers confirm that the crustaceans were digested, rather than having wandered into the feces after the fact. "If the crustacean had just wandered in there, even if it had been stepped on by a dinosaur, it would mostly be together," Chin said. "These pieces of crab are scattered throughout the coprolites."

For more ancient facts, here are the world's oldest animals and what they eat.