A remarkable fossil discovery made just recently in China has provided fresh insight into the workings of the Cretaceous — the era when dinosaurs ruled the land. The findings, published in Scientific Reports, suggest that dinosaurs not have always been at the top of the food chain.
According to the find, even small mammals of the time were capable of hunting and eating dinosaurs. Far from being helpless prey for reptilians, mammals seem to have been active hunters as well.
The story starts in 2012, when lead author Jordan Mallon of Carleton University, Department of Earth Sciences, and his colleagues unearthed a remarkable fossil. The fossil was found in the Lujiatun Member of the Lower Cretaceous Yixian Formation in China. The fossil actually contains remains from two species: Repenomamus robustus, a small mammal, and Psittacosaurus lujiatunensis, a bipedal, beaked dinosaur. Both creatures probably died around the age of adulthood 125 million years ago.
But this is where things get interesting.
Based on their findings, scientists hypothesized a volcanic mudflow buried and preserved R. robustus and P. lujiatunensis as the mammal was attacking the dino. Not only are there no other bite marks on the dinosaur’s skeleton, but this lack of bite marks suggests that R. robustus was actively hunting its larger adversary.
The tail of the R. robustus, which measures 46.7 centimeters in length, is the only missing part. However, the complete skeleton of P. lujiatunensis, which measures 119.6 centimeters from head to tail, exists. The dinosaur is depicted vividly in the fossil, lying on its front with its legs folded under it and its neck and tail curled to the left. The small mammal is perched on the dinosaur’s left side, which curves to the right.
The mammal’s left paw is grasping the dinosaur’s slightly forward-shifted lower jaw, making for a fascinating fossilized tableau. The mammal’s left hind leg is caught under the dinosaur’s folded left leg, and the dinosaur’s hind paw is gripping the mammal’s left shin. Even the teeth of the predator, R. robustus, were found embedded in the prey, P. lujiatunensis‘ ribcage.
The significance of this finding goes far beyond the fossils themselves. These two fossils could cast doubt on the long-held view of dinosaurs as top predators.
