The old meets the new: the boom of a Chinese building unveils dinosaur bones

At the end of a newly constructed street of towers in Yanji City, in northern China, lies an exposed cliff, where paleontologists pick up rocks 100 million years old in search of Prehistoric bones.

Like many fossil excavation sites in China, it was discovered by accident.

The rapid construction of the city in China has created a mother chain of dinosaur fossils. While bulldozers have uncovered prehistoric sites in many countries, the scale and speed of Chinese urbanization is unprecedented, according to the United Nations Development Program.

Perhaps no one has grasped the scientific opportunity better than Xu Xing, sober and unpretentious flag bearer for China's new fame in paleontology. The energetic seeker has named more dinosaur species than any living paleontologist. He ran between the excavation sites to collect specimens and allowed scientists to better understand how birds evolved from dinosaurs.

Matthew Lamanna, curator at the Carnegie Museum of Natural History in Pittsburgh, said that Xu is "widely regarded as one of the most important, if not the most important, paleontologist of dinosaurs working in China today."

"Xu Xing is A-M-A-Z-I-N-G," writes Kristina Curry Rogers, paleontologist at Macalester College in St. Paul, Minnesota, in an email.

Two years ago, Xu's colleague at the Beijing Chinese Academy of Sciences, Jin Changzhu, was visiting his family in Yanji when he heard about fossils discovered on a construction site. A preliminary inspection revealed what appeared to be a dinosaur shoulder bone.

Less than an hour's drive from the North Korean border, the mid-sized city quickly built residential blocks. Seen from an airplane, Yanji looks like a Legoland of new buildings with pink and blue roofs, but there is a long, empty lot of rocky hillsides exposed: the excavation site.

When Xu arrived in Yanji, he acknowledged that the site could fill the gaps in the fossil record, noting the relative scarcity of bones recovered from the Late Cretaceous period, about 100 million years ago. An analysis of the volcanic ash layers revealed the age of the site. Xu now supervises a team of scientists using steel picks, chisels and needles to study the exposed side, where the geological layers resemble a cake of red and gray layers.

The site delivered partial skeletons of three ancient crocodiles and a sauropod, a giant plant-eating dinosaur that included some of the world's largest land animals.

"This is a major feature of paleontology here in China: many works actually help scientists find new fossils," said Xu while he used a needle to pull out the fossils. debris of a crocodile skull partially exposed.

Born in 1969 in western China, in the Xinjiang region, Xu did not choose to study dinosaurs. Like most university students of his day, he was named major. His love for the field grew during the years of graduate school in the 1990s, while feathered dinosaurs found in ancient Chinese lakes attracted worldwide attention.

When Xu and Jin discovered fossils in Yanji in 2016, city authorities suspended the construction of adjacent high-rise buildings, according to a national law.

"The developer was really not happy with me," said Xu, but the local government has since adopted its new celebrity status.

The city is now facilitating Xu's work and has even built an on-site police station to protect the flying's fossils. Once the excavations are completed, a museum is planned to display the recovered fossils and photos of Xu's team at work.

This is not the first museum to commemorate Xu, whose prodigious fieldwork has taken him across China and has resulted in numerous articles in top-level scientific journals.

Toru Sekiyu, a paleontologist at the Fukui Prefectural Dinosaur Museum in Japan who participated in the Yanji excavation, called his Chinese colleague a "leading paleontologist".

But Xu is quick to point out the role that good fortune has played in his career.

"To publish articles and discover new species, you need new data, you need new fossils," he said, adding that the search for new species was not something that the scientist can plan.

"My experience tells me that you really need luck, in addition to your hard work. Then you will be able to make important discoveries. "

With excavations in Inner Mongolia, Liaoning, Yunnan and other Chinese provinces, Xu patiently monitors the excavations, sometimes chiselling for years before knowing their ultimate meaning.

Although his findings are very diverse, much of his career has been devoted to understanding the evolution of dinosaurs into modern birds.

China is an ideal place for this study. Two decades ago, rare fossils of dinosaurs with traces of feathers were found in ancient lake bottoms in northeastern China. This discovery, which allowed scientists to demonstrate that birds came down from dinosaurs, was possible because the mixture of volcanic ash and fine-grained shale in the lake bottoms had preserved soft tissue fragments, including feathers – unlike the majority of dinosaur fossils, which contain only bones. .

Since then, a flood of new dinosaur bones discovered in China has helped scientists rewrite their understanding of the tree of life in different ways.

Xu has been at the forefront of research into how dinosaurs have evolved into feathers and flying. In 2000, he described a curious dinosaur the size of a pigeon with four feathered members, apparently first wings that allowed the animal to fly or hover. In 2012, he detailed a carnivorous tyrannosaur, which also had a plumage – raising questions about the initial purpose of the feathers.

Xu now thinks that the early plumage of the dinosaurs may have played a role in the isolation and display even before the flight feathers grew. He co-authored a 2010 article that examined fossilized melanosomes – packets of pigments giving rise to color in modern bird feathers – in order to infer the likely colors of dinosaur feathers. Some species probably had white and brown feather rings; others had bright red plumage on the head.

By adopting a new technology, his team also uses CT scanners to study the inside of fossils and build computer simulations in 3D to draw conclusions about the range of movement of a dinosaur.

One of the fossils currently being examined by Xu, discovered on a construction site in Jiangxi Province, will shed light on how modern bird breeding systems have evolved from dinosaurs, he says.

In addition to the praise of the profession, Xu's work has caught the attention of schoolchildren in many countries, who send him handwritten notes and dinosaur pencil drawings, many of which are hanging in his Beijing office.

Xu responds to each letter, email and SMS by asking a question about dinosaurs. "I think it would be weird or rude not to do it," he said. But in the age of social media, Xu has refrained from signing up to WeChat, the dominant messaging platform in China, because "I do not think I can find the time to read all the new messages."

Back at the Yanji site, a colleague brings him a big rock with a sauropod vertebra exposed for examination.

The bone has a spongy texture, which, according to Xu, results from the respiratory system of the animal. Like modern birds, he believes that sauropods breathe using both lungs and distributed airbags, which can leave an impression in the bones.

Xu uses a brush to remove dirt to inspect the fossil more closely.

"Basically, we are rebuilding the evolutionary tree of life," he said. "If you have more species to study, you have more branches on this tree, more information on the history of life on Earth."