Fossils show the tangled skeletons of Psittacosaurus (dinosaur) and Repenomamus (mammal) and their interactions shortly before death.

NOTE: The scale bar is equal to 10 cm.

Credit: Gang Han Canadian and Chinese scientists have described an unusual fossil from about 125 million years ago that shows the dramatic moment a carnivorous mammal attacked a herbivorous dinosaur bigger. Dr Jordan Mallon, paleontologist at the Canadian Museum of Nature and co-author explains: “Two animals locked in a life-or-death battle are intimately intertwined and this is one of the pieces of evidence. first to show true mammalian predatory behavior toward dinosaurs.

” The study’s authors were published in the journal Scientific Reports.The presence of fossils challenges the view that dinosaurs posed little threat from mammals of their contemporaries during the Cretaceous period, when dinosaurs were the dominant animals.

This rare fossil is now in the collection of Weihai Ziguang Shi Yan School Museum in Shandong province, China.The well-preserved fossil dinosaur was identified as a Psittacosaurus, about the size of a large dog. Herbivorous psittacosaurs were among the earliest known horned dinosaurs and lived in Asia during the early Cretaceous period, about 125 to 105 million years ago.

The mammal in the fossil pair is a badger-like animal, known as Repenomamus robustus. Although not large by dinosaur standards, it was one of the largest mammals of the Cretaceous period, at a time when mammals did not yet dominate the Earth.Fossils show the tangled skeletons of Psittacosaurus (dinosaur) and Repenomamus (mammals), with enlarged sections showing mammals biting into dinosaur ribs and grabbing prey. The scale bar is equal to 10 cm.

Credit: Gang Han Prior to this discovery, paleontologists knew that Repenomamus ate dinosaurs, including Psittacosaurus, due to fossilized baby bones of herbivores found in the stomachs of mammals. “The coexistence of these two animals is not new, but what is new to science through this incredible fossil is the predatory behavior it exhibits,” Mallon said.Fossils were collected in China’s Liaoning province in 2012, and both skeletons are nearly complete.

Their integrity is due to the fact that they come from an area known as the Liujitun Fossil Bed, which has been dubbed the “Chinese Pompeii”. The name refers to the many fossils of dinosaurs, small mammals, lizards, and amphibians in the area, animals that were suddenly mass buried by landslides and debris after one or many volcanic eruptions.

The existence of volcanic material in the rock matrix of the studied fossils was confirmed after analysis by Dr. Aaron Lussier, mineralogist of the Canadian Museum of Nature.The Psittacosaurus-Repenomamus fossil was in the care of study co-author Dr. Gang Han in China, who attracted the attention of paleontologist Xiao-Chun Wu of the Canadian Museum of Nature.

Close examination of the pair of fossils shows that Psittacosaurus was lying upside down, with its hind legs folded to the sides of its body. Repenomamus’ body rolled to the right and it rested on its prey, with the mammal grabbing the larger dinosaur’s jaws.

The mammal was also biting into some ribs, and Repenomamus’s hind legs were gripping the dinosaur’s hind legs. Dr Mallon said: “The weight of evidence suggests that an active attack is taking place.Mallon, Wu and their colleagues ruled out the possibility that the mammal was simply scavenging a dead dinosaur. The dinosaur’s bones, for example, had no teeth marks, indicating that it was not scavenger but prey. And it’s unlikely the two animals would have become so entwined if the dinosaur was already dead before the mammals found it.

The position of Repenomamus on Psittacosaurus suggests that it was also an invader. The modern world has known the analogy of smaller animals attacking larger prey. Mallon and Wu note that some solitary coyotes have been known to hunt larger game, such as reindeer and domestic sheep. And in the African savannah, wild dogs, jackals and hyenas will attack live prey and the prey will collapse, often in shock.

“It may be the case that as shown in the fossil record, Repenomamus actually ate Psittacosaurus while it was still alive, before both were later killed,” Mallon explained.

The team speculates in their paper that volcanic sediments from the Lujiatun fossil beds in China will continue to yield new evidence of previously unknown species interactions in the rest of the lake. fossil record.