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Despite the great birdosaur fiasco, birds are still dinosaurs



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Posted: Friday, June 23, 2000 | 3:15 a.m.
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GEORGE JOHNSON ON SCIENCE : Despite the great birdosaur fiasco, birds are
still dinosaurs
By George Johnson

I was forced to learn to spell archaeopteryx in 1989, when my daughter Nikki
came home from first grade at Meramec School reciting
"A-R-C-H-A-E-O-P-T-E-R-Y-X."

Her class was just starting to learn to spell, and the teacher assigned them
that word right off the bat. "If you can spell archaeopteryx," she told
them, "you can spell anything." Every kid in that class learned how to spell
archaeopteryx, and, in doing so, felt they could learn anything they set
their mind to. Good teacher.

Archaeopteryx ( pronounced archie-OP-ter-iks) is the first bird for which we
have clear fossil evidence. About the size of a crow, the first fossil was
found in a Jurassic limestone quarry in Bavaria in 1861. It had the clawed
fingers and long bony tail of a dinosaur, with the wishbone and feathered
wings of a bird.

For more than a century, people have argued about archaeopteryx. Did
archaeopteryx evolve from a dinosaur, or from some other reptile? It is
difficult for a nonpaleontologist to appreciate the heat with which this
seemingly dry question has been, and is being, argued.

Boiling more than a century of ferocious argument down to a few lines, the
preponderance of evidence favors a dinosaur ancestor. Archaeopteryx is
remarkably like a therapod dinosaur called velociraptor. You may remember
velociraptors as the scary guys that stalked the kids in the kitchen in the
film "Jurassic Park."

Like velociraptor, archaeopteryx has an unusual swivel-jointed wrist, a
long, very deep shoulder blade, a fused collarbone (familiar as the
"wishbone" of Thanksgiving turkeys), and many other shared features.

As in all good scientific fights, evidence hasn't discouraged dispute.
Despite a mountain of evidence that birds evolved from dinosaurs, a few
scientists I will call the die-hards still refuse to accept this conclusion.

Even in today's issue of the journal Science, there is an article by one of
those die-hards, Alan Feduccia, arguing the case against the bird-dinosaur
link. It's guys like these that make science fun.

What should have been the final nail in the die-hards' coffin, the "smoking
gun" proof of a dinosaur-bird direct link, was the discovery in 1996 in
China of dinosaurs with feathers. The first of these, called
sinosauropteryx, has no wings but is covered with a light featherlike fuzz.
A dinosaur with a feather coat.

"Not really feathers," object the die-hards, "just fuzz."

Then, last year, there was a report from the same Chinese fossil beds of a
dinosaur with real feathers and birdlike wings. The remarkable fossil was
purchased at a fossil show by a dinosaur artist named Stephen Czerkas, who
named it archaeoraptor.

The paper he wrote describing it was turned down by Science and Nature, two
major scientific journals, but National Geographic went on to publish an
article about it in November. I wrote a column about it that same week. The
birdosaur, as newspaper reports called it, appeared to be the missing link
between dinosaurs and birds.

The birdosaur turned out to be a hoax, however. The glued-together rock slab
is a composite, containing the body of a bird and the tail of a
velociraptorlike dinosaur.

How was the fake uncovered? Like the two slices of bread on a turkey
sandwich, this fossil has two "halves" of rock sandwiching the fossil
itself. Czerkas had one piece of bread and the turkey meat. A Chinese farmer
came forth with the other piece of bread, a slab containing the impression
of the dinosaur tail - along with the rest of the dinosaur, and no bird.

"Knew it!" crowed the die-hards.

But out of the rubble of the birdosaur fiasco, other very exciting fossils
have come to light from the same Chinese fossil fields, and they are not
fakes.

Called caudipteryx (that's caw-DIP-ter-iks), meaning "tail feathers," the
fossil dinosaur has large feathers on its tail and arms. Two were discovered
in 1998, and a third beautifully preserved specimen was reported this month
at the fifth International Meeting of the Society of Avian Paleontology held
in Beijing.

"If it has feathers, it must just be some kind of bird we don't know much
about," object the die-hards. Paleontologists disagree. While caudipteryx
has a handful of birdlike features, including feathers, it has many features
of velociraptor dinosaurs, including short arms, serrated teeth, a
velociraptorlike pelvis, and a bony bar behind the eye. Paleontologists who
have studied the new fossils describe caudipteryx as sitting on a branch of
the dinosaur family tree between velociraptor and archaeopteryx.

It seems feathers are not a distinguishing trait of birds. They first
evolved among the dinosaurs. Because the arms of caudipteryx were too short
to use as wings, feathers probably didn't evolve for flight. Instead, they
probably served as insulation, much as fur does for mammals. Flight is
something that certain kinds of dinosaurs achieved as they evolved longer
arms. We call these dinosaurs birds.

George Johnson is a biology professor at Washington University.

-- 
Terry W. Colvin, Sierra Vista, Arizona (USA)
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