University of Chicago scientist Paul Sereno reconstructs the skeleton of the newly-discovered Raptorex on September 17, 2009. This dinosaur is a smaller ancestor of Tyrannosaurus rex. (Photo: AFP PHOTO/AAAS/Mike Hettwer)
Tiny T. rex
A newly found fossil challenges scientists' thinking about T. rex
(Map: Jim McMahon)
Scientists recently identified the fossil of a dinosaur that had the same features as those of Tyrannosaurus rex—only in miniature.
This new species of dinosaur, named Raptorex kriegsteini [RAP-tur-ex kreeg-STEE-nee], had the same extra-large skull, sharp teeth, tiny arms, and powerful legs as T. rex—only it was 9 feet tall and weighed only about 150 pounds. That may not seem "mini" nowadays, but the average T. rex was 40 feet tall and weighed more than 10,000 pounds!
Raptorex, or the "mini T. rex," as some are calling the discovery, lived about 125 million years ago in what is now northern China. That's about 35 million years before T. rex terrorized the Earth.
New Theory About T. rex
Paleontologists, or scientists who study fossils, are finding that the Raptorex discovery is teaching them a lot about T. rex. Scientists had thought T. rex's stumpy arms developed gradually during the dinosaur's time on Earth. The researchers believe the Raptorex fossil overturns this theory.
The old thinking was that T. rex descended from smaller dinosaurs with longer forearms, and then developed its tiny arms as an advantage to its species. Large forearms, said scientists, would have thrown off the balance of these giant hunters, while smaller arms would have made it easier for them to move quickly when chasing prey. But now Raptorex is leading scientists to believe that T. rex inherited its tiny arms from these smaller ancestors.
This new dinosaur is "a very significant find" for understanding the development of T. rex, paleontologist Thomas Holtz of the University of Maryland told National Geographic News.
"We didn't know where and when in the history of the tyrannosaurs this arm shortening occurred," explained Holtz.
Scientists believe Raptorex would have had feathers similar to that of an ostrich. They believe it hunted pig-size plant-eating dinosaurs and turtles that lived near the lake where it was discovered.
Raptorex Returns Home
The Raptorex fossil was dug up without permission, taken out of China, and sold to a dealer. Raptorex kriegsteini is named after the father of Henry Kriegstein, a private fossil collector, who bought it from a dealer.
Kriegstein contacted paleontologist Paul Sereno of the University of Chicago and asked him to examine the fossil. Sereno identified the scientific value of the fossil and convinced Kriegstein to donate it to science. By examining fragments of sand found on the skeleton, Sereno was able to determine from which general region of China the fossil was taken. Soon the fossil will return to its homeland to be displayed at a museum in China's Inner Mongolia region.
"[Raptorex] is more than just a Chinese specimen," Sereno told BBC News. "It has given us some real insights into our own tyrannosaurs here in North America. So it really belongs to science. It belongs to the world."
"Fossils like these should be protected . . . or there's a chance they could disappear forever," Sereno told National Geographic News.
Even though scientists don't know exactly where the Raptorex fossil was discovered, Sereno is hopeful that the find will help lead to the discovery of other important dinosaur specimens.
IS THAT A FACT?
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