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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. |
