The fossil consists of two, nearly complete fossilized skeletons that have been intertwined for approximately 125 million years. The larger skeleton belongs to a dog-size, plant-eating dinosaur known as Psittacosaurus. The smaller skeleton atop the dinosaur belongs to Repenomamus robustus—a meat-eating mammal that would have been about the size of a badger.
“The mammal is gripping the lower jaw of the dinosaur, and it’s kind of holding the dinosaur down and biting into its ribs,” explains Jordan Mallon, a paleobiologist at the Canadian Museum of Nature and co-author of the new study describing the find, published in the journal Scientific Reports.
“I remember when I first looked at it,” he says. “My jaw dropped and my eyes bulged out of my head, because it’s such a fantastic fossil.”
The mammal-vs-dino fossil hails from a rocky outcrop known as the Lujiatun Member of the Lower Cretaceous Yixian Formation—or what some scientists refer to as “Chinese Dinosaur Pompeii,” due to the heavy amount of volcanic activity in the area at the time. With ash build up everywhere and seasonal rains, it’s thought that mudslides were common—and extremely sudden.
“They sort of come out of nowhere,” says Mallon, who has experienced similarly slippery conditions during field work in Alberta, Canada. “These volcanic mudflows would habitually wipe out the animals living in the environment, including this new fossil we described.”
The dinosaur and mammal were instantaneously covered in ash and mud, preserving the details of their mortal struggle.
“I’ve never seen anything like it before,” says Stephen Brusatte, a University of Edinburgh vertebrate paleontologist and author of The Rise and Reign of the Mammals.
“Preserving any part of an animal for 125 million years is hard enough,” says Brusatte, who was not involved in the new study. “But capturing two animals locked in combat, it seems like a miracle.”
Mammal vs. dino: Anatomy of an attack
While the experts assumed from the start that the fossil depicted a mammal attacking a dinosaur, they wanted to be sure.
