British scientist describes rare discovery of a dinosaur eating a mammal

Mammal's foot in a dinosaur fossil. Copyright: Alex Dececci.

A new study led by Dr David Hone of Queen Mary University of London, published in the Journal of Vertebrate Paleontology, records this very rare discovery of an incident of a dinosaur having eaten a mammal. (Note: The mammal would not have been a human ancestor).

The fossil is of a small, feathered dinosaur called Microraptor that lived in the ancient forests of what is now China in the Early Cretaceous Period around 120 million years ago. Microraptor was about the size of a crow and had long feathers on its arms and legs and was likely gliding from tree to tree, hunting out small animals to eat.

Although the specimen was first described in 2000, many years later Professor Hans Larsson of McGill University in Montreal spotted what others had missed – the remains of another animal inside it – the foot of an ancient mammal preserved between the ribs. Together with Dr Hone, and colleagues from Canada, the USA and China, they have now described this additional discovery.

The mammal foot is almost complete and belonged to a very small animal, about the size of a modern mouse. Analysis of the bones suggest that it was one that predominantly lived on the ground and was not a good climber, making it an interesting option for Microraptor that likely spent most of its time in the trees.

Previous studies have revealed other Microraptor specimens containing a bird, a lizard and a fish. So with this evidence for eating mammals, it is clear that this dinosaur had a diverse diet and was not a specialist on any given option. It is not certain if the dinosaurs in question had directly preyed upon and eaten these animals or found them already dead and had scavenged them (or a mixture of both) but the mammal at least falls into the range of typical prey size predicated for a predator the size of Microraptor.

Dr Hone’s co-authors on the paper include Dr Alex Dececchi, Mount Marty College, Dr Corwin Sullivan at the Department of Biological Sciences, University of Alberta, and Professor Xu Xing at Institute of Vertebrate Paleontology and Paleoanthropology, Beijing.

Dr David Hone, from Queen Mary University of London, said: “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.

“While this mammal would absolutely not have been a human ancestor, we can look back at some of our ancient relatives being a meal for hungry dinosaurs. This study paints a picture of a fascinating moment in time – one of the first record of a dinosaur eating a mammal - even if it isn’t quite as frightening as anything in Jurassic Park.”

Dr Alex Dececchi, from Mount Marty College, said: “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."

Research paper: Hone, D.W.E., Dececchi, T.A., Sullivan, C., Xu, X. & Larsson, H.C.E. 2022. Generalist diet of Microraptor zhaoianus included mammals. Journal of Vertebrate Paleontology.  https://www.tandfonline.com/doi/full/10.1080/02724634.2022.2144337