Canadian and Chinese scientists have described a rare fossil from about 125 million years ago that shows a rare moment in time when a carnivorous mammal attacked a larger dinosaur for food. a plant.
“The two animals were locked in mortal combat, closely related, and this is one of the first evidences showing the actual predatory nature of a mammal in a dinosaur,” explained Dr. Jordan Mallon, paleobiologist at the Canadian Museum of Nature and co-author of the study published in the journal Scientific reports.
The presence of the fossil challenges the view that dinosaurs had little threat from their mammalian contemporaries during the Cretaceous, when dinosaurs were the dominant animals. The rare fossil is now in the collections of the Weihai Ziguang Shi Yan School Museum in China’s Shandong Province.
The dinosaur in the well-preserved fossil was identified as a species of Psittacosaurus, which was about the size of a large dog. Plant-eating psittacosaurs are among the oldest known horned dinosaurs and lived in Asia during the Early Cretaceous, from about 125 to 105 million years ago. The mammal in the fossil pair is a badger-like animal, called Repenomamus robustus. Although not large by dinosaur standards, it was one of the largest mammals of the Cretaceous period, a time when mammals had not yet come to rule the Earth.
Before this discovery, paleontologists knew that Repenomamus preyed on dinosaurs including Psittacosaurus because of fossilized bones of the herbivore’s baby found in the mammal’s stomach.
“The co-existence of these two animals is not new, but what is new to science through this unique fossil is the predatory behavior it exhibits,” said Mallon.
The fossil was collected in China’s Liaoning Province in 2012, and the two skeletons are almost complete. Their completeness is due to the fact that they come from an area known as the Liujitun fossil bed, which has been called “China’s Dinosaur Pompeii.”
The name refers to the many fossils of dinosaurs, small mammals, lizards and amphibians in the area, animals that were suddenly buried mostly in mudslides and debris after one or more volcanic eruptions. The existence of volcanic material in the rock matrix of the study fossil was confirmed after the analysis of the Canadian Museum of Nature mineralogist Dr. Aaron Lussier.
The Psittacosaurus-Repenomamus fossil is in the care of study co-author Dr. Gang Han in China, who brought it to the attention of Canadian Museum of Nature paleobiologist Xiao-Chun Wu.
A close examination of the fossil pair shows that Psittacosaurus was lying down, with its hind limbs folded on either side of its body. The body of Repenomamus twists to the right and sits on top of its prey, with the mammal gripping the jaws of the larger dinosaur. The mammal also bit off some of the ribs, and Repenomamus’ back foot was holding onto the dino’s hind leg. “The weight of the evidence suggests that an active attack is underway,” said Dr. Mallon.
Mallon, Wu and colleagues ruled out the possibility that the mammal was simply scavenging for dead dinosaurs. Dinosaur bones don’t have tooth marks, for example, suggesting they weren’t scavenged, but dug up. And it’s unlikely that the two animals would have been so entangled if the dinosaur had died before the mammal arrived. The position of Repenomamus above Psittacosaurus suggests that it was also the aggressor.
Analogies of small animals attacking larger prey are known in the modern world. Mallon and Wu note that some lone wolves are known to hunt large game, including caribou and domestic sheep. And in the African savanna, wild dogs, jackals and hyenas attack prey that is still alive, with the prey collapsing, often in a state of shock.
“It’s probably the case with what the fossil shows, that Repenomamus actually ate Psittacosaurus while it was still alive—before both were killed in a gruesome aftermath,” Mallon explained.
The research team speculated in their paper that volcanically derived deposits from the Lujiatun fossil beds in China will continue to provide new evidence of species interactions, otherwise unknown from other fossil records.
Jordan C. Mallon, A rare fossil captures the struggle for existence in the Mesozoic era, Scientific reports (2023). DOI: 10.1038/s41598-023-37545-8. www.nature.com/articles/s41598-023-37545-8
Courtesy of the Canadian Museum of Nature
Citation: Unusual fossil shows unusual evidence of mammal that attacked dinosaurs (2023, July 18) retrieved on July 18, 2023 from https://phys.org/news/2023-07-unusual-fossil-rare-evidence- mammal.html
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