Rare fossil discovery in China hints at mammals hunting dinosaurs in epic showdown

A stunningly-detailed rare fossil discovered in China suggests that some mammals may have actively hunted dinosaurs that were several times larger than their size. The 125-million-year-old fossil shows the mammal Repenomamus biting the horned dinosaur Psittacosaurus. According to Smithsonian Magazine, the bones uncovered in 2012 comprise a cat-sized animal called "Repenomamus robustus" entangled with a beaked dinosaur known as "Psittacosaurus lujiatunensis." The Psittacosaurus is on its side and its skeleton is curled in a semicircle. The smaller Repenomamus is tucked up inside against the dinosaur. Experts believe that based on their positions the animals were in a tussle before they died. Their skeletons became immortalized when a nearby volcanic eruption entombed them in a quick wave of ash and mud. 

Experts believe that based on their positions the animals were in a tussle before they died. Their skeletons became immortalized when a nearby volcanic eruption entombed them in a quick wave of ash and mud. "We already knew that mammals did occasionally prey on at least baby dinosaurs," Jordan Mallon, the study co-author and paleobiologist at the Canadian Museum of Nature, told NPR. "What's new here is even a fully grown Psittacosaurus wasn't necessarily safe from these smaller mammalian predators." According to Mallon, "Our best guess is that the mammal was in the middle of attacking the dinosaur" and that it "appears to have been particularly gutsy or voracious."

The finding is incredibly fascinating as such behavior is rare to record in a fossil. In this case, they seemed to be buried and preserved in the middle of the attack. One of the smaller mammals' paws is clutching the larger dinosaur's lower jaw, while another grips a hind leg. "And the lower jaw of the mammal is biting onto some of the dinosaur's ribcage," he shared. Also, it was noted that its bones did not have any bite marks. "These fossilized moments in time," Mallon said, "really allow us to make these quantum leaps in our inferences to be able to reconstruct these ancient ecosystems."

Other experts seem to disagree with the interpretation. "The mammal's hand inside the mouth of the dinosaur, which had a high bite force, suggests at least the dinosaur was dead at the time of burial, or it would have easily sliced off the hand," Hans Larsson, a paleontologist at McGill University, told New Scientist. "The awkward interlocking legs between the two suggest both were dead or tumbled while being buried. In this case, I think there is not enough evidence to say with full confidence the mammal was the predator caught in the act of subduing its prey."

In any case, the finding of such a well-preserved fossil is still exciting. "This is the kind of specimen that paleontologists dream of—a pristine snapshot of ancient behavior and ecology," Raymond Rogers, a geologist at Macalester College who was not involved in the study, told Science. "If this remarkable specimen is the real deal, it is a one-in-a-million find."