Dino feathers
Strongest evidence birds descended from dinosaurs
John Noble Wilford - New York Times
April 25, 2001

Paleontologists have discovered in China a fossil dinosaur with what are
reported to be clear traces of feathers from head to tail, the most
persuasive evidence so far, scientists said, that feathers predated the
origin of birds and that modern birds are descendants of dinosaurs.
Entombed in fine-grained rock, the dinosaur's unusually well-preserved
skeleton resembles that of a duck with a reptilian tail, altogether about 3
feet in length. Its head and tail are edged with the imprint of downy
fibers. The rest of the body, except for bare lower legs, shows distinct
traces of tufts and filaments that appear to have been primitive feathers.
On the backs of its short forelimbs are patterns of what look like modern
bird feathers.
Other dinosaur remains with apparent featherlike traces have been
unearthed in recent years, but nothing as complete as this specimen, paleontologists
said. Etched in the rock like a filigree decoration surrounding the
skeleton are imprints of where the down and feathers appear to have been.
The 130-million-year-old fossil was found a year ago by farmers in the
Liaoning Province of northeastern China. After a careful analysis by
Chinese and American researchers, the fossil animal was identified as a
dromaeosaur, a small, fast-running dinosaur related to velociraptor. These dinosaurs
belong to a group of two-legged predators known as advanced theropods.
The findings are described in the latest edition of the journal Nature by
the discovery team led by Dr. Ji Qiang, director of the Chinese Academy of
Geological Sciences in Beijing, and Mark A. Norell, chairman of
paleontology at the American Museum of Natural History in New York. The specimen, on
loan from China, went on public display at the museum on Wednesday and is to
undergo CAT scans there.
"This is the specimen we've been waiting for," Norell said in a museum
statement. "It makes it indisputable that a body covering similar to
feathers was present in nonavian dinosaurs."
This dinosaur's forelimbs were too short to have supported wings, Norell
said in an interview, and so it was flightless. But some of its bone
structure, notably the furcula, or wishbone, and the three
forward-pointing toes, bears similarities to those of birds. Other recent discoveries of
birdlike dinosaurs and dinosaurlike birds have encouraged support of the
theory of a dinosaur-bird ancestral link.
A few dissenters, however, particularly among ornithologists, continue to
dispute the theory. They argue that birds evolved from some earlier, yet
undiscovered, reptile. They said that previously found fossils associating
featherlike traces with dinosaur skeletons were too mixed-up to determine
if the feathers belonged to the dinosaur and not to a primitive bird buried
at about the same time.
These dissenters said that the marks that were being interpreted as
feathers in the new fossil could be impressions from the dinosaur's skin.
But the Chinese and American researchers said the new discovery enabled
them to see with microscopes how the feathers and downy fluff were attached to
the dinosaur's body. A similar, though not as complete, fossil find
reported last month by another Chinese-American team, including Dr. Richard Owen
Prum, a paleontologist at the University of Kansas who specializes in bird
fossils, appeared to reinforce the conclusion that some theropod dinosaurs
indeed had feathers.
Accordingly, most paleontologists consider the case for such a
dinosaur-bird link now virtually airtight. Dr. Hans-Dieter Sues, a dinosaur
paleontologist at the Royal Ontario Museum in Toronto, said the two discoveries from
Liaoning Province "further strengthen the case for the theropod-bird
connection, but also establish that feathers originated and eventually
diversified in nonflying, nonavian theropod dinosaurs."
Not that these particular dinosaurs were ancestors of birds; but they may
be descendants of the ancestors. Some dromaeosaurs evolved earlier than
birds.
Feathered, flightless birds are known to have existed as early as the
145-million-year-old Archaeopteryx, found in Germany in the 19th century.
Norell said the feathered fossil showed that there was "a more general
distribution of feathers than in birds alone." Studying theropods that
lived later than the first birds, he explained, should provide insights into
bird evolution just as related "chimps and gorillas and lemurs help us
understand human evolution."
In a commentary that accompanied the journal report, Sues wrote that,
because feathers must have been present before the origin of birds and
flight, they "clearly evolved for some purpose other than flight, perhaps
thermal insulation or behavioral display (or both)."
The Chinese and American researchers favored the idea that the feathers
served to keep the dinosaurs warm. In that case, the discovery seemed to
support the theory that some predatory dinosaurs were warm-blooded like
modern birds rather than cold-blooded like other reptiles. They would thus
have required something like feather covering to maintain their body
temperature.
"Insulation implies higher metabolic rates than for the average reptile,"
explained Peter Makovicky, a paleontologist at the American Museum who is
completing his doctoral studies at Columbia and has made a detailed study
of the specimen.
The region of northeastern China where the skeleton was uncovered has some
of the world's richest fossil beds, which have been actively explored over
the last decade. Between 145 million and 120 million years ago, the land
was covered by many lakes and erupting volcanoes rained down fine ash. This
probably buried animals as soon as they died, increasing the chance of
their remains fossilizing and surviving the ages.
Two other dromaeosaurs have been recovered from these fossil beds:
Sinornithosaurus, a small dinosaur first described in 1999, and
Microraptor, the smallest known theropod, found last year. But one specimen, reported
in the early 1990s, turned out to be a hoax, a clever composite of bones and
some featherlike imprints.
Researchers said they were sure the latest find is genuine. The skeleton
was embedded in two slabs sliced from the mudstone. Close examination, the
scientists said, show that both sides "match up perfectly," which would be
extremely difficult to fake.

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