In China's Cretaceous Pompeii, dinosaurs were found preserved in perfect sleeping poses 125 million years old. Unlike Pompeii, they were not killed by a pyroclastic flow. Scientists now think an invisible, odorless eruption of volcanic CO2 silently suffocated them in their sleep, and a slow-moving mudslide entombed them before their bodies could decay. One fossil captures a weasel-shaped mammal with its teeth sunk deep into a dinosaur's ribs, frozen mid-kill.
A Sudden, Silent End
In the Liaoning Province of northeastern China lie the Lujiatun beds, the oldest layers of the famed Yixian Formation. Dating back approximately 125 million years to the Early Cretaceous, this site shows a three-dimensional prehistoric ecosystem. The area's preservation has led some to call it the "Cretaceous Pompeii."
The exact cause of the mass burial is a subject of scientific debate. The initial theory suggested a single, massive volcanic eruption buried the animals in hot ash. Current research suggests a more complex scenario. The animals were likely killed and then rapidly buried by lahars—fast-moving volcanic mudflows triggered by heavy rains on ash-laden ground. This rapid entombment in fine sediment prevented decay and scavenging, preserving skeletons in lifelike, three-dimensional poses. Some animals, like the newly-discovered burrowing dinosaur Changmiania liaoningensis ("eternal sleeper from Liaoning"), appear to have been buried alive while resting in their dens.
An Ancient Battle, Interrupted
The Lujiatun beds have yielded hundreds of exquisitely preserved fossils, but one shows a mammal and a dinosaur locked in mortal combat. Discovered by farmers in 2012, the fossil shows a badger-sized mammal, Repenomamus robustus, attacking a bipedal, plant-eating dinosaur, Psittacosaurus lujiatunensis. The Psittacosaurus, roughly the size of a large dog, is lying prone, while the mammal is on top, its left paw gripping the dinosaur's jaw and its teeth sunk deep into the ribs.
This fossil is direct evidence of predatory behavior by a Mesozoic mammal on a dinosaur. Paleontologists had previously found the bones of a baby Psittacosaurus inside the fossilized stomach of a Repenomamus, but this new find shows the mammal was bold enough to hunt prey significantly larger than itself. The lack of any other bite marks on the dinosaur's skeleton indicates this was an active hunt, not scavenging of an already-dead carcass. The fight was dramatically cut short when a volcanic mudflow engulfed both animals, preserving their struggle for 125 million years. Other important finds from the area include clusters of juvenile Psittacosaurus, suggesting they lived in groups, and early bird-like dinosaurs such as Mei long, found curled in a sleeping posture.
💡Fun Facts
*Psittacosaurus*, meaning "parrot lizard," is named for its powerful, parrot-like beak.
*Repenomamus robustus* was one of the largest mammals of its time, but still only measured about 1.5 feet (47 cm) in length.
The Yixian Formation is famous for preserving soft tissues, including the first evidence of feathered dinosaurs.
Fossils of the small dinosaur *Changmiania liaoningensis* suggest it was a powerful runner and a burrower, likely to escape predators.
The Lujiatun fossil beds are an active paleontological site and not open to the public. However, many of the key fossils are displayed in major Chinese museums. The Liaoning Paleontological Museum in Shenyang is a primary repository for fossils from this region. The Paleozoological Museum of China in Beijing also holds significant fossils from the Yixian Formation. Museum hours are typically 9:00 AM to 4:30 PM, closed on Mondays.
Admission
Admission to the Paleozoological Museum of China is typically around 20 CNY.
Accessibility
The museums are generally accessible, with flat surfaces and elevators. The actual fossil sites are on rough, undeveloped terrain.