3,000-pound birdlike fossil found

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Chicago Tribune article and illustration of Gigantoraptor...

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3,000-pound birdlike fossil found 
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By Robert Mitchum
Tribune staff reporter

June 13, 2007, 1:12 PM CDT

Dinosaur hunters working in Inner Mongolia today announced they have discovered 
the fossil of an enormous birdlike dinosaur 300 times heavier than its closest 
relatives.

Dubbed Gigantoraptor erlianensis, the species lived 75 million to 95 million 
years ago, late in the dinosaur era. The relatively complete fossil specimen 
was about 25 feet long, 11.5 feet high at the shoulder and would have weighed 
more than 3,000 pounds, yet exhibited birdlike characteristics including a 
beak, hollow bones and, very likely, ornamental feathers.

The report in this week's issue of Nature adds complexity to the story of bird 
evolution, a gradual shrinking process by which the huge thunder lizards were 
reduced to small, light and feathered creatures. The discovery of such a large 
hybrid reveals the twists and turns that evolution can take.

"This species is the largest of its kind, and a lot bigger than anyone ever 
expect these animals to get," said Peter Makovicky, assistant curator of 
dinosaurs at the Field Museum in Chicago. "When animals get big they tend to 
look less birdlike; for instance, we have no birds that reach a ton or more in 
body size. But here, some of the birdlike traits are actually retained or 
developed even though the animal is very large."

Dr. Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology 
in Beijing and colleagues found the fossil in the Erlian Basin in northeastern 
China. Xu said the region has attracted attention since the 1920s but that 
several interesting discoveries have emerged in the area recently, including 
several other feathered dinosaurs.

By analyzing the state of growth in one of the fossil bones, researchers 
estimate the dinosaur was relatively young, about 11 years old at the time of 
death. That suggests a full-size Gigantoraptor may be even larger than this 
particular fossil indicates.

While the fossil does not prove the dinosaur had feathers, researchers agree 
that it likely did.

"One would assume Gigantoraptor is feathered since its ancestry lies with a 
group of animals that we know also had feathers," Makovicky said.

However, its feathers would definitely not be used for flight.

"Being 3,000 pounds heavy, no one would expect this species to fly," said Xu.

Experts say feathers likely first evolved as a form of insulation, similar to 
fur in mammals. But because retaining body heat is less of an issue for larger 
animals, researchers believe Gigantoraptor's feathers would have served a 
different purpose: helping the animal communicate.

"Dinosaurs were clearly animals that liked to display to each other; that's why 
they had crests, horns, and bumps," said Philip J. Currie, professor of 
dinosaur paleobiology at the University of Alberta. "Feathers almost certainly 
developed first as insulation in small species, but other dinosaurs surely 
started using them as display. A species might have crown feathers at the top 
of its head or feathers at the end of its tail."

rmitchum@tribune.com 
Copyright (c) 2007, Chicago Tribune