Small mammal caught preying on dinosaur in Chinese fossil

A bizarre fossil found in China appears to have caught a small mammal in the act of attacking and attempting to eat a dinosaur.

Researchers believe the 125-million-year-old diminutive battle scene shows the mammal preying on the larger (but still small) dinosaur when both animals were quickly covered by a volcanic mud flow. The results of a study led by palaeontologists at China’s Hainan Vocational University of Science and Technology and their Canadian colleagues are published in Scientific Reports.

The small mammal is Cretaceous carnivore Repenomamus robustus. Though the fossiis missing the tip of the tail, the preserved creature is 46.7 centimetres long. Its prey, a bipedal, beaked relative of Triceratops called Psittacosaurus lujiatunensis, is completely preserved and is 119.6 cm long. Both animals are believed to have been subadults at the time of death.

Pencil drawing of rat like mammal biting small beaked dinosaur
An artist’s reconstruction of the scene captured by the fossil discovered in China. Credit: Michael Skrepnick.

Dinosaurs were the undisputed rulers of the Earth during the Mesozoic aeon. At this time in Earth’s history mammals were living in the shadows and usually no larger than a modern squirrel. A cousin of the species encased in battle, the more than one-metre-long Repenomamus giganticus, is the largest known mammal that lived in the Cretaceous.

The fossilised struggle between predator and prey was found in 2012 in the Lujiatun Member of the Lower Cretaceous Yixian Formation in China.

The mammal was found lying on top of the dinosaur’s left side.

R. robustus’s teeth were sunk into the dinosaur’s ribs when the animals died. The lack of other bite marks is a strong indication that the small mammal wasn’t scavenging, but indeed preying on the Psittacosaurus.

It is not the first instance of a Repenomamus seeing a dinosaur as a source of food. In 2005, a Repenomamus robustus skeleton was found with juvenile Psittacosaurus remains in its stomach.

“Mesozoic mammals are usually depicted as having lived in the shadows of their larger dinosaurian contemporaries, but this new fossil convincingly demonstrates that mammals could pose a threat even to near fully-grown dinosaurs,” the authors write.

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