Fossil offers ultra rare piece of evidence showing a dinosaur eating a mammal

EDMONTON — An international team of researchers has uncovered an extremely rare piece of evidence that dinosaurs ate mammals. 

The foot of a small mammal about the size of a mouse was found preserved inside the gut contents of a Microraptor zhaoianus, a small feathered dinosaur from the early Cretaceous period, according to a new study published in the Journal of Vertebrate Paleontology. There is a lone earlier report of a dinosaur specimen with mammalian gut contents, however, that report pertains to a species that isn't closely related to Microraptor.

It’s extremely rare to find conclusive evidence of a dinosaur’s diet because of how difficult it is for a dinosaur’s gut contents to be preserved, says Corwin Sullivan, associate professor in the Department of Biological Sciences and co-author of the paper. 

“There was always interest in [Microraptor’s] diet because there had been previous specimens that contained remains of different vertebrates inside the rib cage, but we have the first one that contains parts of a mammal,” he notes.

The Microraptor was found within Jurassic and Cretaceous lake deposits in what is now northeast China.

Previous Microraptor specimens from this area have been found with gut contents of a fish, bird and lizard, indicating that these small dinosaurs had diverse diets. However, it remains unclear whether Microraptor consumed the contents in a predator-prey relationship or by scavenging. Researchers can only say conclusively that Microraptor was carnivorous.

Sullivan says information about dinosaurs’ diets is a key piece in the puzzle to learning more about what was going on at the time they roamed the Earth.

“We’re slowly gathering pieces of information about these past ecosystems and the animals that inhabited them. So what this discovery does is fill in a little bit of information in that it’s showing the diet of Microraptor was even broader, even more generalist, than we thought previously.”

“That tells us something about this animal and, by extension, tells us that there were generalist carnivores in these ancient ecosystems — that that niche existed.”