Dinosaur-Bird Dinosaur-Bird
F8 THETORONTOSTAR Sunday, October24, 1999 |
T. rex: Top reptile or a proto-turkey? |
A foot-high fossil confirms modern birds descended from dinosaurs, many experts sayBY GUY GUGLIOTTA
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The source of Czerkas's
enthusiasm is a fossil he spotted at a gem and mineral show and
bought for his Dinosaur Museum in Blanding, Utah. He immediately
recognized what he had: another spectacular find from an ancient
lake bed in China's Liaoning province, emerging as one of the
most important sources of Cretaceous remains in the world. For Czerkas and many paleontologists, the new discoveries are the most convincing- and perhaps the last --- evidence necessary to convince hold outs that the bipedal carnivorous dinosaurs known as theropods are the ancestors of modern birds. |
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"For me, the debate's been over for 10 years," says Philip Currie, head of dinosaur research at the Royal Tyrrell Museum in Drumheller, Alta., who helped identify the new fossils. "With these newcomers, we don't have just one type of dinosaur. It's kind of overwhelming." The dinosaur-bird link has important implications for paleontology. If archaeoraptor and its ancient cousins had feathers, as the new fossils powerfully suggest, then they were likely to have been warm-blooded, not the cold-blooded reptilians of the textbooks. And while the other two new Liaoning dinosaurs-recovered by Chinese paleontologists from conventional excavations-did not have arms powerful enough to fly, they must still have needed their feathers for warmth or ornamentation. The first of these, Sinornithosaurus millenii, "Chinese bird-reptile of the millennium," was an eagle-sized animal with barracuda like teeth and very long claws. Beipinosaurus inexpectus, "surprising lizard from Beipiao," was two metres tall-the latest feathered dinosaur yet discovered. And logically, Currie says, the dinosaur-bird theory should also embrace the larger theropods, such as the velociraptor of Jurassic Park, and even Tyrannosaurus rex, the emperor of prehistoric meat eaters. But "there's no evidence of feathers on tyrannosaurus," Currie says, and a warm-blooded, adult tyrannosaurus would probably generate enough body heat to offset the need for extra insulation. Still, National Geographic magazine is a believer. The November issue depicts a tyrannosaurus parent roaring at the edge of its nest next to a hatchling covered with fuzz. This proselytizing may eventually prove to be the theory's undoing, says Larry Martin, a University of Kansas paleo-ornithologist who believes flying dinosaurs and birds developed along parallel tracks, rather than evolving one from the other. "The National Geographic is already committed but it will turn out to be an embarrassment," Martin predicts. "When people start to think of a tyrannosaurus with feathers, they won't accept it." Also, Martin says that while archaeoraptor and similar fossils have skeletal characteristics that bear a surface similarity to those of birds, these features differ in key respects from the clear evolutionary line that begins with archaeopteryx, the 145 million-year-old German fossil generally regarded as the first true bird. Finally, he noted, by the time the Liaoning stratum was laid down some 120 million years ago, "you're at the point where birds were already abundant and diversifying and changing." But Currie says there is no reason why "relic species" cannot exist side-by-side with their descendants and, indeed, Liaoning is a rich site where an entire ecosystem-dinosaurs, reptiles, fish, birds, small mammals and plants-appears to have been virtually frozen in time. Scientists theorize that this unique formation of the Liaoning site was caused by an exploding volcano that sent a ball of poison gas rolling into the lake bed, where it quickly asphyxiated every living thing. This was followed immediately by a rain of fine volcanic ash, which killed the bacteria in the water and mixed with the suspended lake mud to create a bath of primordial goo. Today the goo has jelled around the dead creatures like a plaster cast, which, when carefully split apart, preserves the outlines of what apparently were once hair and feathers. "We can finally say that some dinosaurs did survive," Czerkas says. "We call them birds." WASHINGTON POST |
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