Scientists may have discovered the first remains of a mammal eaten by dinosaurs

The foot of an ancient mammal the size of a mouse

The Microraptor lived in present-day China in the Early Cretaceous period some 120 million years ago. The size of a crow, Microraptor had long features on its arms and legs and might have glided across different trees, hunting for prey.

The specimen was first described around 22 years ago - but it took two decades for Professor Hans Larsson of McGill in Montreal to spot what everyone else missed. Along with Dr. Hone, and colleagues from Canada, the USA, and China, Larsson found the foot of an ancient mammal preserved between the ribs of a Microraptor.

"It’s so rare to find examples of food inside dinosaurs so every example is really important as it gives direct evidence of what they were eating," said Hone.

So, what mammal was it?

The foot seemed to belong to a very small animal about the size of a modern mouse. As per bone analysis, it appeared to be a mammal that primarily lived on the ground and was not the best climber. It made for an easy meal for the Microraptor that spent most of its time in the trees.

The Microraptor has previously been found with a bird, lizard, and a fish in its stomach

Other Microraptor species have previously been found with birds, lizards, and fish. Now, with fresh evidence for eating animals, it is evident that the dinosaur enjoyed eating a variety of meals and wasn't too fussy about any given option. While it isn't yet clear if the dinosaur directly found the animal and ate them or scavenged them, the mammal certainly falls within the range of "typical prey size predicted for a predator the size of a Microraptor", as per the release.

"The great thing is that, like your housecat which was about the same size, Microraptor would have been an easy animal to live with but a terror if it got out as it would hunt everything from the birds at your feeder to the mice in your hedge or the fish in your pond," said Dr. Alex Dececchi from Mount Marty College.

Study Abstract

Gut contents are extremely important for inferring trophic interactions between extinct species. These are, however, very rare in the fossil record and it is not always possible to accurately identify both the carnivore and the consumed organisms. Here we describe the remains of a small fossil mammal foot preserved inside the body cavity of the holotype specimen of the small feathered dinosaur Microraptor zhaoianus. This adds to the known diversity of diet for this genus, which also consumed birds, fish, and lizards. Previous interpretations that Microraptor was an arboreal hunter of birds and adept hunter of fish are not supported. Although the various known stomach contents would be plausible prey items based on size, there is no clear evidence that any of them were predated rather than scavenged, and Microraptor likely did both and foraged in multiple habitats.