Did the Mesozoic era also have a "Pompeii"? Hello! Ancient "friends" under the ash of Jehol volcano

Science Times reporter epic

In the northern Hebei-western Liaoning-eastern Inner Mongolia region of my country, there is a world-class fossil treasure house. Over the past 100 years, a large number of fossil species with important scientific research significance have been discovered here, covering almost all biological categories in the transition from the Mesozoic to the Cenozoic, providing extremely important fossil evidence for studying major theoretical issues such as the origin of birds and flight, the origin of eutherians, the origin of angiosperms, and geological changes and biological co-evolution.

On November 2, the "Ancient Rehe - Special Exhibition of Important Fossil Discoveries in the Mesozoic Era" (hereinafter referred to as the Special Exhibition) opened at the National Museum of Natural History. Rehe Province was a provincial-level administrative region established during the Republic of China period, including parts of today's western Liaoning, northern Hebei, and eastern Inner Mongolia. Famous Mesozoic biotas were distributed here, which lived in the middle of the Mesozoic Era, about 160 million to 120 million years ago.

Special exhibition site. Photo by Shi Ji

Volcanic eruptions create unique burial environments

The volcanic ash in the fossil-bearing strata in the Rehe region records the process of volcanic eruptions. The toxic gases emitted by the volcano caused the death of a large number of organisms, and the volcanic ash quickly covered the remains of the organisms, allowing the fossils to be preserved extremely well. At the same time, frequent magma activities caused the collapse of the regional ecosystem, thereby accelerating the process of biological evolution.

In the Jehol region, the Mesozoic strata are well developed, and a wide variety of paleontological fossils are preserved in them. Some fossils even preserve extremely rare soft tissues: wing veins, mouthparts and bristles of insects; skin (scale) impressions of amphibians and reptiles; membranes and fibrous skin structures of pterosaurs; feathers of dinosaurs and birds; fine structures such as hair of mammals...

In 1923, American geologist Gleip discovered and proposed the "Jehol System" for the first time in Lingyuan, western Liaoning. With the discovery of more fossils, in 1962, Chinese paleontologist Gu Zhiwei called the fossils contained in this stratum the Jehol Biota, among which the most abundant and most indicative fossils are three categories: crustaceans (Oriental leaf-breasted ostracods), insects (Trichopodidae) and vertebrates (Lycodon). In 1983, paleontologist Hong Youchong named the animal group contained in this group of strata the Yanliao Insect Group based on the composition of insect fossil species found in northern Hebei and western Liaoning.

Since then, a large number of geologists and paleontologists have come forward one after another, devoted a lot of wisdom and sweat to exploring the mysteries of the origin and evolution of life, and achieved a series of world-renowned scientific research results.

Reconstructing ancient life under volcanic ash

About 160 million to 120 million years ago, during the middle and late Jurassic period and the early Cretaceous period, active geological processes produced a large amount of greenhouse gases, and many areas of the world were submerged by seawater. At that time, the Jehol region was densely covered with freshwater lakes, with a warm and humid climate, and a variety of animals and plants thrived here. Sturgeons and wolffish swam leisurely in the lakes, and turtles and dragons roamed everywhere. On land, gymnosperms such as cycads, ginkgo, and pines and cypresses grew luxuriantly, and angiosperms also grew by the water. Primitive placental mammals such as the Chinese Jurassic beast, the climbing ancestral beast, and small feathered dinosaurs shuttled through the forests or open areas one after another. Pterosaurs and primitive birds glided or flew in the sky and between the trees.

The special exhibition consists of three units: "Entering the Fossil Treasure House of the Rehe Region", "Treasures of Paleontology in the Rehe Region" and "Evidence of the Flying Dragon in the Sky". A total of 131 rare fossils (including 130 type specimens) are exhibited, covering almost all biological categories in the transition from the Mesozoic to the Cenozoic. At the same time, the special exhibition combines multimedia interactive exhibits to lead the audience into the ancient Rehe region from all directions and angles, interpreting the wonderful life stories that occurred in the Mesozoic era, and finding and deciphering the evidence of the "flying dragon in the sky".

"Many fossils may look plain in appearance, but they are all very interesting," said Zhang Yuguang, deputy director of the National Museum of Natural History. Due to being quickly buried by volcanic ash, the true appearance of some ancient creatures was preserved. For example, the two fossil specimens of Yang's Jinzhousaurus and Psittacosaurus in the exhibition even have their skin imprints clearly visible.

"Humans are placental mammals, and this fossil, which looks like a small mouse, is the ancestor of placental mammals." Zhang Yuguang pointed to the fossil "stars" such as the world's earliest "placental mammals", Jurassic beasts, and explained, but this does not mean that humans evolved from Chinese Jurassic beasts. It can only be said that it already has similar characteristics to our early ancestral types.

The Jurassic and Cretaceous systems in the Rehe area have preserved relatively complete biological communities and systems from more than 100 million years ago due to their unique fossil burial types, which have solved the difficult problems of the origin and evolution of many biological categories in the Mesozoic Era. The biological communities here are even hailed as "one of the most important paleontological discoveries in the world in the 20th century" and "Pompeii of the Mesozoic Era."

From November 2nd to December 3rd, let us go to the National Museum of Natural History to explore the mysterious world of the Mesozoic Era in the Rehe area and feel the wonder of the evolution of life.