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| Month
Day,2003 |
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First
Dinosaur Found With Its Body Intact
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Discovery
of Remarkably Preserved Fossil Dinosaur from China on Display at American Museum
of Natural History Beginning April 25
American Museum of Natural History
New
York -- A team of Chinese and American scientists announced today in Nature the
discovery of a remarkably preserved, 130-million-year-old fossil dinosaur covered
from head to tail with downy fluff and primitive feathers. It is the first dinosaur
found with its entire body covering intact, providing the best evidence yet that
animals developed feathers for warmth before they could fly.
The dinosaur
was unearthed last spring by farmers digging in the famous fossil beds of northeastern
China's Liaoning Province. It is described in the science journal Nature by a
team led by Ji Qiang, of the Chinese Academy of Geological Sciences, and Mark
Norell, Chairman of the Division of Paleontology at the American Museum of Natural
History.
The researchers have identified the fossil animal as a dromaeosaur,
a small, fast-running dinosaur closely related to Velociraptor with a sickle claw
on its middle toe and stiffening rods in its tail. Dromaeosaurs belong to a group
of dinosaurs known as advanced theropods, two-legged predators including Tyrannosaurus
rex, with sharp teeth and bones strikingly similar to those of modern-day birds.
"This
fossil radically modifies our vision of these extinct animals," said Dr. Norell,
whose discoveries in the Gobi Desert of Mongolia have led to new ideas about theropods
and bird origins. "It shows us that advanced theropod dinosaurs may have looked
more like weird birds than giant lizards."
Entombed in two slabs of fine-grained
rock, the dinosaur's skeleton resembles that of a large duck with a long tail
and an oversized head (indicating that the animal was a juvenile). A small fish
is embedded in the rock near its left foot. Its head and tail are covered with
downy fibers. Other parts of its body sprout tufts or sprays of filaments resembling
primitive feathers, and the backs of its arms are adorned with branched structures
like the barbs of a modern bird feather.
The spectacular fossil is on loan
from the National Geological Museum of China to the American Museum of Natural
History, where it will be publicly displayed for the first time beginning Wednesday,
April 25. While in the United States, it will also travel to Texas to be imaged
with a special CAT scan machine to give scientists a more detailed, three-dimensional
view of the skeleton.
Since 1995, when the first dinosaur with primitive
feathers, Sinosauropteryx, was discovered in the Yixian Formation of the Liaoning
fossil beds, several new species of dinosaurs with feather-like structures have
been found there. But in most cases the fossils were jumbled or incomplete-making
it unclear how the featherlike structures related to the animal's body. Critics
of the widely accepted theory that modern birds evolved from dinosaurs have questioned
the validity of these "feathered" dinosaurs, claiming that the feather-like structures
were not primitive feathers or that the specimens were mixed-up fossils of primitive
birds and dinosaurs.
The detail on the newly discovered dromaeosaur is
so fine that it allows scientists to see how the primitive feathers were attached
to the dinosaur's body. "This is the specimen we've been waiting for," says Ji
Qiang. "It makes it indisputable that a body covering similar to feathers was
present in non-avian dinosaurs."
Because dromaeosaurs are more primitive
than birds, this fossil helps make the case that feathers developed before flight.
In small, flightless dinosaurs like this one, feathers may have evolved as an
essential piece of equipment for staying warm.
"Modern birds are warm-blooded
and their feathers play an integral role in keeping them warm, so a reasonable
idea is that non-avian dinosaurs developed primitive feathers at the same time
that they developed warm-bloodedness," says Norell. "It's conceivable that smaller
dinosaurs like this one and even the young of larger species like Tyrannosaurus
rex may have needed featherlike body coverings to maintain their body temperature."
Scientists
have yet to determine if the new dromaeosaur represents a new species. But they
do know that it shares some anatomical characteristics with two other dromaeosaurs
discovered in the same fossil beds: Sinornithosaurus, a small theropod dinosaur
first described in 1999, and Microraptor, the smallest known theropod dinosaur,
found last year.
A Treasure Trove of Fossils in China
Consisting
of layers of volcanic and sedimentary rock, the Yixian Formation in China's Liaoning
Province has yielded an enormous variety of fossil fish, birds, insects, reptiles,
shrimp, flowers, mammals, and dinosaurs dating back to late Jurassic and early
Cretaceous times-between 145 and 120 million years ago. At that time, the region
was dotted with freshwater lakes and volcanoes. Volcanic explosions rained fine
ash into the lakes, and animals that died or fell into the water were quickly
buried in the fine-grained sediment at the bottom. Because they were buried so
quickly, with so little oxygen available to promote decay, the fossil animals
found in the Yixian Formation have delicate features almost impossibly preserved
from feathers and fish scales to patterns on insect wings.
"These fossils
have dramatically changed the way we understand what life was like during late
Jurassic and early Cretaceous times," said Ji Qiang.
How Are Dinosaurs
Related to Birds?
In the last two decades, other birdlike dinosaurs
and dinosaurlike birds have been unearthed at fossil sites around the world, including
those in Madagascar, Mongolia, Patagonia, and Spain. Together with the Chinese
fossils, they provide strong evidence that birds evolved from theropod dinosaurs.
Yet a small group of scientists still argue against the dinosaur-bird link, insisting
that birds evolved independently from some earlier, yet undiscovered, reptile
much farther back in time.
The link between dinosaurs and birds was first
noted in the mid-1800s by naturalist Thomas Henry Huxley, who observed that birds
were built much like reptiles, but with a beak instead of teeth and with three
reptilian fingers hidden inside their wings. In the 1970s, John Ostrom of Yale
University launched a meticulous comparison of the anatomical features of dinosaurs
and the oldest known bird, Archaeopteryx.
Today we know that theropod dinosaurs
and birds share more than 100 anatomical features, including a wishbone, swiveling
wrists, and three forward-pointing toes. Among all advanced theropods, the swift-running
dromaeosaurs are thought to be the most closely related to birds.
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