By Will Dunham
WASHINGTON (Reuters) – While there is no doubt that many Mesozoic mammals were food for dinosaurs, it may come as a surprise to learn that some mammals also feasted on dinos.
A remarkable fossil found in northeastern China shows a pagansac badger-like mammal attacking a plant-eating dinosaur 125 million years ago, pinning down its prey and sinking its teeth into the victim’s ribs, scientists said Tuesday.
Dating back to the Cretaceous period, the four-legged mammal Repenomamus robustus – the size of a domestic cat – was significantly larger than the two-legged dinosaur Psittacosaurus lujiatunensis – the size of a medium-sized dog. The scientists confirmed their suspicions that they were suddenly engulfed in volcanic lava and buried alive during a deadly battle.
“Dinosaurs were always bigger than their contemporaries,” says Jordan Malone, a research paleogeologist at the Canadian Museum of Nature in Ottawa. Journal of scientific reports.
“Here we have good evidence of a small mammal preying on a large dinosaur, something we wouldn’t have imagined without this fossil,” Malone added.
Most mammals in the Mesozoic Era, the age of the dinosaurs, were sensible-sized bit players in the larger theater of life, good enough not to be someone else’s lunch. Repenomamus shows that at least some mammals gave as good as they got.
“I think the key here is that the Mesozoic food web was more complex than we thought,” Malone said.
The area in Liaoning Province is called the “Pompeii of China” because of the animal fossils buried by the volcanic eruption.
Examining the remains was like analyzing a crime scene. Repenomamus sits atop a prone Psittacosaurus, biting its ribs and grabbing its jaws and hind legs. Repenomamus measures 1-1/2 feet (47 cm) long. Psittacosaurus was 4 feet (120 cm) long. Both are considered to be not fully mature.
“There have been examples of carnivorous dinosaurs preying on plant-eating dinosaurs before, but there is no example of a mammal preying on a dinosaur,” said Xiao-chun Wu, a paleontologist at the Canadian Museum of Nature and research associate.
Finding fossils showing animal interactions is rare. Another fossil discovered in Mongolia in the 1970s shows two dinosaurs – a predatory Velociraptor and a plant-eating Protoceratops – fighting 80 million years ago before being buried alive, possibly in a collapsing sand dune.
The researchers dismissed the idea that the fossils of Repenomamus and Psittacosaurus were simply fossilized mammals.
“For one mammal, it’s trying to rule over dinosaurs, which doesn’t have the label of a pseudo-hypothesis,” Malone said.
“Secondly, there are no bite marks on the dinosaur bone, which we would expect if it had been sitting for a long time, exposed to brutality. Ultimately, the mammal’s hind leg was caught by the bent back leg of the dinosaur. That would not have happened if the dinosaur had been dead when it encountered the mammal,” Malone added. .
Although Psittacosaurus was an early relative of the horned dinosaur lineage, it lacked frontal horns and head tusks. It had a parrot-like beak for cutting plant material.
One of the largest mammals of the dinosaur era, Repenomamus had short, stubby legs, a long tail, sinuous body, a strong skull, and barbed teeth. Malone compared its appearance to a Chinese ferret-badger.
There was earlier evidence of the dino-eating habits of Repenomamus. A Rhaponomamus fossil from the same area had the bones of a baby Psittacosaurus in its stomach.
“What’s unique about our fossil is that Repenomamus was able to cope with large dinosaur prey,” Malone said.
(Reporting by Will Dunham, Editing by Roselba O’Brien)