120 Million-year-old Fossil Proves Dinosaurs Ate Mammals, Debunking Previous Theories

A rare piece of evidence indicating that dinosaurs ate mammals was unearthed by an international team of experts. They found a mouse-sized mammal foot inside the gastrointestinal contents of a Microraptor zhaoianus, a small feathered dinosaur from the early Cretaceous period.

Researchers detailed their findings in their study, titled "Generalist Diet of Microraptor zhaoianus Included Mammals" published in the Journal of Vertebrate Paleontology. There has only been one earlier account of a dinosaur having mammalian gastrointestinal contents, and it is not closely linked to Microraptor.

Rare Evidence of Dinosaurs Eating Mammals

The level of difficulty to retain a dinosaur's stomach contents is so challenging that definitive proof of a dinosaur's diet is exceedingly rare, says associate professor Corwin Sullivan from the Department of Biological Sciences and co-author of the work.

He noted that scientists have always been curious as to the diet of Microraptor even before finding specimens that included the remnants of other vertebrates inside their ribs. But it is their first time to see a fossil of a mammal inside the dinosaur's stomach, SciTech Daily reports. The specimen of Microraptor was found in Jurassic and Cretaceous lake sediments in northeast China.

Microraptor individuals previously found were also found in the same location but most of them only have avian, fish, and reptile stomach contents, which means they have varied diets and were carnivores. Although, scientists are unsure whether the contents were devoured after a predator-prey interaction.

Meanwhile, this particular specimen found in 2000 had contents that show the dinosaur ate mammals. Sullivan said that information regarding dinosaur diets is an important piece of understanding how these huge reptiles lived during the Cretaceous period.

The team is progressively collecting information about these former ecosystems and the species that once inhabited them. The recent findings fill in information by demonstrating that Microraptor's diet was even broader than previously thought. That means there is more about this species that scientists may not know, as well as the generalist carnivores that existed millions of years ago.

What Did Dinosaurs Eat?

Paleontologist and research scientist Dr. Jordan Mallon explained to Science World that dinosaurs had varying diets. That means some ate plants, others ate meat, and there are also omnivores who eat both. He noted that dinosaurs had varying diets so that the environment would be able to support them just like other species today.

Although, carnivorous dinosaurs had to switch their diet over time to become herbivores or omnivores to adapt to their changing environment. On the other hand, paleontologist Dr. Donald Henderson said that herbivores had a more difficult time switching to carnivores because of how specialized their digestive systems were.

It seems that being a herbivore was not without challenges even though it was more advantageous for them to eat plants than hunt their prey. Unlike animals, plants have a cell wall that makes them hard to digest so herbivores evolved to have specialized teeth and broader guts to swallow and digest them.

Herbivorous dinosaurs had flat teeth for stripping and grinding plants, while carnivorous dinosaurs had sharp teeth to make it easier to cut into the meat. Some carnivorous dinosaurs feasted on lizards, turtles, early mammals, and even dead animals.