Did mammals take on the dinosaurs?

The discovery of a spectacular fossil in China challenges our understanding of the roles established between dinosaurs and mammals during the Cretaceous.

PALEONTOLOGY For 230 million years, dinosaurs and mammals co-existed on our planet – and if, like many paleontologists, you consider birds to be dinosaurs by descent, then we still coexist today.

Judging from the fossil record, there was a long status quo where mammals would hide from carnivorous dinosaurs, but could apparently live more peacefully among herbivorous dinosaurs.

Now the discovery of a fascinating fossil in China has led Canadian researchers to conclude that some mammals may have violated the peace, and began hunting herbivorous dinosaurs to consume them.

The rare fossil is 125 million years old and involves a mammal in mortal combat with a dinosaur three times its size.

The dinosaur under attack is a herbivorous Psittacosaurus lujiatunensis, which was the size of a large dog. Although the dinosaur was a herbivore, the mammal, a carnivorous Repenomamus robustus, was on a difficult mission, as it was only the size of a small badger.

Researchers from the Canadian Museum of Nature believes the fossil duo is one of the first pieces of evidence of a mammal attacking a dinosaur.

“It was not only big dinosaurs consuming small mammals. Sometimes mammals were also able to consume dinosaurs,” says study author Jordan Mallon, a palaeobiologist working for the Canadian museum’s research team.

The fossil was discovered in Liaoning province in China, also known as ‘China’s Pompeii’, where dinosaurs, mammals and other creatures were buried and preserved by mud and debris from ancient volcanoes.

According to the researchers, both animals died in the battle after the mammal attacked the dinosaur.

“The lack of bite marks on the dinosaur skeleton, the position of the mammal on top of the dinosaur, and the mammal’s grip and bite all signal that the mammal was chasing the weakened dinosaur when the two were suddenly buried by a volcanic flow,” says Jordan Mallon.

Nobody can be sure which vertebrate class might have come out on top that day, in that particular battle. In the long run, both Cretaceous species faced extinction.

The fossil reveals a prehistoric duel between vertebrate classes, a hunting sequence frozen in rock. This illustration shows their possible appearance; the mammal may have chased down the tiring reptile.