This armored dinosaur is a paleontologist’s dream. Named Borealopelta in 2017, the dinosaur’s fossil preserves a great deal of its bony armor in place. In fact, the animal is so intricately preserved that paleontologists have been able to work out the dinosaur’s color — rusty red above and lighter below. But the so-called “northern shield” still has secrets to reveal. Inside the dinosaur, protected by its bones, are the remnants of the ankylosaur’s last meal.
Paleontologists know relatively little about what dinosaurs actually had for lunch. For carnivorous animals, the key evidence often comes from bitten bones and petrified poop that contains bone shards and muscle fibers.
Among herbivores, fossil feces can narrow down a few menu options, but fossilized gut contents have been more contentious. It can be difficult to tell whether tatters of plants found inside a plant-eating dinosaur’s skeleton were remnants of a last meal — or simply happened to get mixed in with the sediment that buried the animal. Just this year, in fact, the gut contents found in a duckbill dinosaur turned out to be prehistoric compost mixed in among the bones during preservation.
“Dinosaurs that become fossils often get buried in the mud or in river channels,” says Caleb Brown of the Royal Tyrrell Museum. These circumstances can create confounding associations of bones and the material inside, which may or may not be the contents of the petrified dinosaur’s stomach.
But Brown says this specimen stands apart — and is the best-supported case for stomach contents in an herbivorous dinosaur. “And it contains the most detail about revealing what the diet was,” he adds. Brown and colleagues have published their study this week in