jueves, 11 de agosto de 2011

Palaeontology - Spectacular Dinosaur finds popping up all over China


Inside an air hangar in the middle of the countryside in China’s Shandong province, 600 kilometers southeast of Beijing, paleontologist Xu Xing is absently watching a tipsy, red-faced tourist. The man has taken off his shoes and plopped down for a photo in front of the fossilized femur of a gigantic hadrosaur—a duck-billed dinosaur that roamed the earth 99 million years ago during the late Cretaceous period. The bone is nestled in a pile of gold fabric and stands about 1.5 meters tall. A sign in Chinese encourages visitors to give it a poke. “Rub, rub a dinosaur bone,” says the ditty, evoking a common local belief that stroking dinosaur bones can bring good fortune. 

Dinosaur footprints in Shandong province are among the remarkable discoveries popping up all over China [Credit: Lu Jinxing/ChinaFotoPress-ZUMA]


Chinese paleontologists have handled a lot of fossils in recent years—the field is flush with new finds in Central Asia. Zhucheng, where Xu does fieldwork, is home to the country’s freshest and most spectacular quarry of skeletons. In a trench not far from the hangar, large fossilized bones are scattered across the surface of the sandstone rock, mixed up haphazardly in a way that suggests a mega-catastrophe happened here nearly 10 millennia ago. 

The trove of fossils at Zhucheng is probably the largest single deposit of dinosaur bones in the world. And it’s just the latest in a string of spectacular discoveries by the 42-year-old Xu, who’s arguably helped uncover more important finds than any other dinosaur hunter on the planet. “I am quite certain that Xu Xing has described more new kinds of dinosaurs than anyone in the history of dinosaur paleontology,” says Peter Dodson, professor of paleontology at the University of Pennsylvania and coeditor of the book The Dinosauria. While Xu forgets precisely how many new species he’s discovered, he believes he’s at “around 30.” In the last 15 years, Xu has contributed to the discovery of feathered dromaeosaurs in Liaoning, theropods in Xinjiang, and the ostrichlike Sinornithomimus in Inner Mongolia—all of which are helping to change the way scientists around the world understand the life and evolution of dinosaurs. 

“China is a very big country with an awful lot of rocks of just the right kind,” explains David Hone, a British paleontologist who spent three years working at Zhucheng. While North America is home to dinosaurs from the late Triassic (228 million to 199.6 million years ago), late Jurassic (161.1 million to 145.5 million years ago), and late Cretaceous periods (99.5 million to 65.5 million years ago), scientists were finding little in between. China, Hone says, is helping to fill in the gaps in the timeline of dinosaur development and in their geographical movements. Similarities between species in North America, Asia, and Europe can help scientists trace dinosaur migration across land masses that no longer exist. Discoveries in Liaoning and Xinjiang are also helping scientists unravel the evolution of modern-day birds, a lineage Xu believes begins with dinosaurs. One of Xu’s most recent discoveries, the chicken-size Xiaotingia zhengi, is giving scientists cause to rethink the classification of the Archaeopteryx, long considered the oldest-known bird. The Xiaotingia zhengi, Xu argues, provides evidence that both species were, in fact, feathered dinosaurs, not full-fledged birds. 

In addition to deepening the understanding of dinosaur development globally, China’s dinosaur explosion has propelled Xu, a homegrown scientist, onto the international stage. Xu grew up in Ili prefecture in western Xinjiang province, a remote Central Asian outback bordering Kazakhstan. When he was assigned to the paleontology department at Beijing University, he had never heard of dinosaurs before reading his admissions document. “I took the paper to my high-school teacher,” Xu says. “He didn’t know what [paleontology] was either—he just said, ‘This is probably a new department. I think it’s high-tech or something like that.’” Xu showed up at school assuming he’d be working with computers. 


Xu Xing excavates at a site in Lujiatun, China. Other paleontologists say Xu has described more new kinds of dinosaurs than any other scientist [Credit: Xinhua Photo-Corbis]


It took years for Xu to embrace the profession. He applied to a master’s program in paleontology only because it would allow him to stay in Beijing. His interest was finally piqued when his department started getting some more unusual fossils to study. Xu still remembers his first small ceratopsian, a horned creature related to the North American Triceratops. “I think, in the end, I was born to be a paleontologist,” he now says. Xu learned English so he could publish in international journals, where he believed the standards were higher. “In the 1990s, there were already some exceptional fossils discovered in China,” he says, “but none of them had attracted attention worldwide. All the papers were published in Chinese journals.” Not only are there language barriers in paleontology, but the style of science is often different in China—with no tradition of argument or peer review—and, in many cases, the science is dated. 

The first Chinese dinosaur was discovered in the 1920s, but for decades the handful of scientists in the field worked without the proper facilities to support their finds. Today, international collaboration and a wider range of funding sources has helped Chinese archeology grow. “There used to be only one or two grants given out [from domestic institutions] every year,” Xu says. “Now there are nine or 10.” China’s rapid development has helped promote archeology in another way—more construction projects mean more chances to discover fossils. As a master’s student, Xu says, it was hard to come by any fossils at all. The pool of available fossils was smaller, and the best were often reserved for more seasoned scientists. Now his office at the Institute of Vertebrate Paleontology and Paleoanthropology is bursting with them. “I remember seeing this tyrannosaur stuff just hanging around [Xu’s] office,” says the British scientist Hone. “Finally Xu said, ‘I’m too busy; do you want to [study] this?’” Hone didn’t hesitate to say yes. 

Although paleontologists have known about the site at Zhucheng for more than two decades, scientists didn’t discover its enormous size until they stumbled on the main quarry in 2008. Since then, the seven-ton tyrannosaur that Hone worked on—a Zhuchengosaurus maximus, from the late Cretaceous—is only one of the nine new species to come out of the 300-meter-long trench. The site sits on the outskirts of a village called Long Gu Xian, or Dragon Bone Village. (The Chinese word for dinosaur translates as “scary dragon.”) Fossils have been popping out of the rocks here for centuries. In addition to being large, the quarry is dense with bones. “The site is quite superlative,” Dodson says. “I couldn’t even think of a story that would explain why all those fossils are there.” The event that killed the species is still a mystery: Xu thinks a landslide ripped the dinosaurs apart and mixed up their bones; Hone suspects the animals were already dead and decomposing when their skeletons were swept to this spot by a massive flood or mud flow. 

The main trench at Zhucheng is filled with duck-billed hadrosaurs. What’s now exciting researchers, however, are the other species scattered more sparsely throughout the site. Only a few bones of the Zhuchengosaurus maximus were found among the hadrosaurs, says Hone. Researchers may not have a complete skeleton yet, but they have the most important part: the maxilla, the upper part of the nose and jaw. “Tyrannosaur maxilli are really distinct from each other,” says Hone, “and this is something incredibly close to T. rex.” 

The site has also produced the only large ceratopsian found in Asia. The absence of ceratopsian fossils on the continent had long baffled scientists. Many North American dinosaur species also populated Asia, suggesting the presence of a land bridge over the Pacific Ocean during the late Cretaceous. But the lack of ceratopsians presented a potential flaw in the theory—one that was solved by the presence of the Sinoceratops, Xu says. In addition to providing more evidence for the existence of a now-submerged link between the two continents, the discovery suggests there are more discoveries to be made. “There are very similar members on both sides of the divide,” says Hone. “Now we’ve got one, we should start finding others.” 

Walking through the trench at Zhucheng, Xu is convinced that there are more discoveries to come. He pauses at the bones of a yet-unnamed species, its skeleton sticking out of the rock. “That is a very, very bizarre dinosaur,” he says happily. “As a scientist, you always want to find a really strange dinosaur.” 





Provided by The Archaeology News Network