Small mammal attacked dinosaur 3 times bigger – 07/18/2023 – Science

Unusual fossils discovered in China depict a fight to the death between a dinosaur and a small mammal that took place 125 million years ago. Contrary to what was probably the rule at the time, however, the aggressor was the small mammal, which launched itself at prey that was almost three times its size.

The actors in this drama are, on the one hand, the Psittacosaurus lujiatunensis, herbivorous dino that had a parrot-like beak and weighed about 10 kg at death; and, on the other hand, the Repenomamus robustusa distant relative of today’s mammals, weighing only 3.5 kg.

Details about the finding have just been published in the specialized journal Scientific Reports, in a study signed by Chinese and Canadian researchers. The team found the nearly complete skeleton of members of both species in a peculiar position, which suggests they were still grappling together at the time they were killed by a volcanic eruption.

To be exact, the mammal’s body was on top of the dinosaur’s left side, and its teeth were sunk into the victim’s ribs. The left front paw of the Repenomamus is gripping the jaw of psittacosauruswhile one of the small predator’s hind legs holds the victim’s shin.

“It is evident that the victim had already collapsed on his belly to the ground – perhaps because of loss of blood, exhaustion or the shock of the attack – and the mammal had begun to devour him, as it was biting his ribs.” explains the study coordinator, Jordan Mallon, linked to the Canadian Museum of Nature and Carleton University, in Ottawa.

Another possibility is that the Repenomamus was acting as a scavenger, eating the corpse some time after death, but Mallon and his colleagues think this scenario is far less likely because there are no bite marks on the little dino’s bones, as is often the case in such cases. The paleontologist points out that the mammal’s other hind leg is trapped by its prey’s bent leg. “So it’s possible that this explains why he couldn’t escape the avalanche of volcanic mud” that preserved the two, he says.

The region where the fossils were found, in the vicinity of the village of Lujiatun, in the province of Liaoning (northeastern China), is famous for the exceptional preservation of species from the Age of Dinosaurs, precisely thanks to the rapid burial of bodies caused by volcanic events.

It can be said that the Repenomamus is a repeat offender. In 2005, paleontologists revealed a fossil of R. robustus whose stomach contents were preserved —and, in the animal’s belly, were the remains of a psittacosaurus newborn. It was the first direct evidence that mammals from the Cretaceous period were capable of hunting dinosaurs. This time, however, the situation is even more dramatic, since the preyed dino was already an adult, while the mammal had not yet reached maturity, judging by the development of its bones.

“I don’t think it’s a coincidence that the Repenomamus be present in both cases,” says Mallon. “It’s one of the largest mammals from the time of the dinosaurs, and it was carnivorous. Furthermore, it is specific to the Lujiatun region, where the state of fossil preservation is impressive. Few other species of fossil mammals and regions of the world meet all these conditions.”

Vaguely resembling a large possum, the Repenomamus belonged to a group of primitive mammals with quite varied lifestyles, including even gliding and semi-aquatic animals. It is possible that it laid eggs, like the platypus, or gave birth to very undeveloped and tiny babies, like kangaroos and other marsupials today.