EDITOR'S DESK
A Giant Mystery
  



 

Fossil Hunters

A team of enthusiastic paleontologists is hard at work in China, seeking to
unravel mysteries such as the link between dinosaurs and birds

By TANG YUANKAI

DIGGING FOR DINOSAURS: Xu Xing, one of China’s top paleontologists, digs at an excavation site in Xinjiang

A few days after the excavation of the largest dinosaur fossil ever found in Asia, Dr. Xu Xing left the discovery site in Qitai, a county in China’s Xinjiang Uygur Autonomous Region. He traveled to Wucaii Bay, 100 km away, to get away from all the excitement and continue with his usual research work.

“I hope to find more dinosaur fossils so that I can figure out the relationships between them. In this way we can draft a dinosaur evolution diagram,” Xu said. Dinosaurs lived for 170 million years on earth and finding out their evolutionary track is important for decoding many life science subjects.

Talented paleontologist

Xu has found and named 15 new dinosaur genuses, and is the paleontologist who has discovered the most dinosaur categories in China. Only 37 years old, he is considered to be one of the most promising paleontologists of the up-and-coming generation.

In the past five years, Xu has published nine papers in the internationally famed magazine Nature and these articles are often cited by international research journals. In 1999, his research work registered 37 citations in the Science Citation Index (SCI), a greater achievement than his predecessors.

However, Xu wasn’t always driven toward dinosaurs. “I held no interest in dinosaurs at all in my college years,” he confessed. He received a master’s degree from the Institute of Vertebrate Paleontology and Paleoanthropology under the Chinese Academy of Sciences after graduation from the Geology Department of Peking University. “I feel lucky to have had the chance to study in this institution and get to know so many prestigious scholars. After that I started down the road of dinosaur research.”

Despite dominating the earth for such a long time, dinosaurs haven’t left many fossils due to the strict conditions necessary for fossils to develop. The fossilization of dinosaur bones depends on factors such as whether the creature had hard bones, whether the dead bodies are buried in proper physical and chemical conditions, and whether the bodies are buried immediately after death and preserved long enough.

“Few creatures can become fossils and even fewer can emerge to the surface of the earth, and then fewer still can get into our hands to be studied,” Xu said.

“We’ve always been worrying that we might miss excavating a fossil or that the fossils might be ruined by fossil dealers,” said Xu’s colleague Zhou Zhonghe, who led a research project that won an outstanding achievement award from the Chinese Academy of Sciences.

Xu and Zhou spend several months a year at excavation sites, living under difficult conditions. In the desert in west China, they have to fetch water from a place that is hundreds of kilometers away.

“On the surface, the information that fossils carry with them is simple, but after careful study, these fossils provide important proof of the evolution theory,” Xu said.

Xu along with other foreign scientists found fossils of a small carnivorous dinosaur that lived about 160 million years ago. Deduced to be the forebear of the giant tyrannosaurus, this kind of dinosaur was given the name Guanlong wucaii. Guanlong is the Chinese term for a dragon that has a crest on the crown of its head. The crest is big and full of air. Wucaii is the name of the place where the fossil was excavated.

Belonging to the tyrannosaurini, a tribe under the tyrannosaurus genus, Guanlong is much smaller than tyrannosaurus. According to the fossils, a Guanlong was 3 meters long and 1 meter tall. The Guanlong wucaii fossils show how the ancestor of the tyrannosaurus evolved from a small carnivorous animal to a large and ferocious one. This evolution took some 100 million years.

The discovery of Guanlong wucaii fossils was accidental. Back in 2002, scientists found two intact dinosaur fossils in the Jurassic stratum of a riverbed in the Wucaii Bay area. One fossil was on top of the other, and one had an unusual crest on its head while the other didn’t. But there were chasms on the head of the latter and scientists hypothesized that the crest might have come off from the head.

A research team led by Xu later studied these fossils and published the research results in that year’s Nature magazine.

From dinosaur to bird

HIDDEN HISTORY: Fossilization of dinosaur bones depends on there having been precise conditions at the time of the dinosaur’s death, millions of years ago

Tyrannosaurini are considered to have been one of the most ferocious dinosaurs and studies on them have continued since the tyrannosaurini were named in 1905. The oldest tyrannosaurini skeleton found so far is aviatyrannis, which lived 150 million years ago. Di-Long, which means “king of the dinosaurs” in Chinese, comes after that, about 130 million years ago. Di-Long was also found by Xu Xing, in Beipiao City in Liaoning Province in 2004, and the discovery was the first in the world. As the Di-Long fossils are more intact than those of the aviatyrannis, Di-Long has become the most widely recognized oldest forebear of the tyrannosaurini.

However, the recent discovery of Guanlong wucaii fossils has overturned the theory of Di-Long being the oldest ancestor of tyrannosaurini, pushing the timeline back 30 million years. As well, scientists believe that the large tyrannosaurini lived mostly during the Cretaceous period (80 million years ago) while Guanlong wucaii lived 160 million years ago. And the bone structure of the Guanlong wucaii has provided new research directions for studies about the little-known coelurosauria.

“The crest of the Guanlong is very special, resembling that of the birds, and this may prove that birds and theropods evolved from the same ancestor,” said Xing Lida, a student of Xu.

“Deinonychus actually is not what has been described in the movie Jurassic Park. In fact they are dinosaurs with feathers instead of the lizard-like skin as you see in the movie,” noted Xu.

Xu said he has found evidence of feathers on the Di-Long fossils. “It’s a decisive discovery that will prove birds and dinosaurs share the same ancestor.”

The controversy of the origins of birds and dinosaurs hasn’t ended as the various arguments made by experts around the world lack sufficient evidence. “Some people just can’t believe how come the ugly dinosaurs turn into beautiful birds. The key to this research is to find the evidence that theropods do have feathers,” Xu said.

In 1996, a batch of small feathered theropod fossils was discovered. The shape and structure of their feathers are exactly the same as that of the modern birds, therefore, they were named zhonghualongniao, with the Latin name sinornithosaurus, meaning Chinese feathered dinosaurs.

“Fossils that have been found prove that dinosaurs are good at running, including the 140-million-year-old archaeopteryx, which is also believed to be a good runner. As a result, many follow the hypothesis that dinosaurs ran to fly and began to grow feathers,” Xu said.

But Zhou prefers the assumption of “tree evolution.” He said that dinosaurs first climbed trees and jumped from one tree to another. During the process, they began to grow feathers and develop the ability to fly. “Through living in trees, dinosaurs improved their body structure and gradually turned to birds,” Zhou said, adding, “But we have little evidence for this assumption.”

Comparing the bone structure of archaeopteryx and deinonychus, Xu pointed out that they have much in common. “There are at least 100 similarities between them, and many of these similarities are unique to birds and dinosaurs, which provides good evidence that birds and dinosaurs are closely related.”

Xu believes that 160 million years ago one dinosaur turned into the first bird on the earth and that bird finally developed into the present-day huge bird family. “Birds incubate eggs, and fossils indicate that dinosaurs also incubate eggs, which means that birds inherited this behavior from their dinosaur ancestor,” he said.

“Even the structure of dinosaur eggs is like that of the birds. The resemblances of the bone structure, incubation behavior and egg structure all prove that birds and dinosaurs are closely related; in other words, birds evolved from dinosaurs.”


China’s Dinosaur Research

ON DISPLAY: A 9-meter tall dinosaur that lived during the late Jurassic period stands in the dinosaur museum in the city of Zigong, Sichuan Province

Research about dinosaurs is based on a variety of fossil and non-fossil records, including body remains, trackways, and trace remains such as eggs and feces. Dinosaurs are considered the best evidence for biological evolution. Their sudden extinction remains a scientific puzzle, and the impetus for scientists from around the world to discover more.

The first Chinese dinosaur to be named was mandschurosaurus, discovered in Jiayin County of Heilongjiang Province in 1902.

Between 1928 and 1931, Chinese scientist Yuan Fuli led an expedition into the northern part of the desert in Qitai, a county in the Xinjiang Uygur Autonomous Region of China, to find two large dinosaur skeletons. This was the first such exploration in Asia and it caused a sensation.

The period between 1933 and 1949 saw the establishment of the foundation work of China’s dinosaur research, led by Yang Zhongjian. Yang finished his studies in Germany and returned home in 1928 and devoted all his life to the study of vertebrate paleontology. Yang is considered the father of China’s vertebrate paleontology research as he has fostered a group of dinosaur fossil excavators and researchers.

In the early 1950s, Zhou Mingzhen,a geology scientist, found fossils of dinosaur and their eggs when he was guiding his students on field work in Shandong Province. Yang also took part in this excavation.

Later, geologists again discovered an intact dinosaur fossil in Xinjiang Uygur Autonomous Region.

In 1959, a joint paleontology expedition by China and the Soviet Union dug out a large number of Hadrosaurus fossils and other dinosaur fossils in 1960.

In 1963, the Chinese Academy of Sciences organized an expedition to conduct a three-year inspection in Xinjiang. The same year, a 15-meter-long Hadrosaurus fossil, the world’s largest, was excavated in Zhucheng, Shandong Province.

The year 1979 was a milestone in China’s dinosaur research history as hundreds of intact dinosaur skeletons were discovered in the city of Zigong in Sichuan Province. In 1987 an open field dinosaur museum was built here, the first in China and Asia.

In 1983, a sauropoda fossil was excavated by an expedition organized by the Chinese Academy of Sciences.

After reform and opening up, China began to seek cooperation on dinosaur research projects and formed expeditions with countries like Britain, the United States, Canada and Japan. Among these, the China-Canada expedition has yielded the best results.

Since 1984, six intact dinosaur fossils have been found, one after another, in Qitai County in the Xinjiang region by Chinese and foreign researchers.

In 1987, a joint expedition by China and Canada in Qitai excavated the then largest dinosaur fossil in Asia, making Junggar Pendi Basin the important base for dinosaur research.

Between 2000 and 2002, a China-Germany expedition inspected the Junggar Pendi Basin and discovered many animal fossils. After three years of research they found these animals had lived 160-170 million years ago and they are of new genuses, different from the ancient vertebrates in other regions of the world.

Dinosaur fossils were also found in Lingwu, Ningxia Hui Autonomous Region. In June 2005, Lingwu was listed as a relic-protection location. This August, fossils excavated here were identified to be the head of diplodocus.

Also in August, the world’s longest-necked dinosaur was found in Xinjiang.