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Fossil Discovery Threatens Theory of Birds' Evolution



For those of you who can't get enough of this story,
and you know that means you, here's how the Paper of
Record reports the plucking of the dinosaurs.  

Ruben's last comment, the last sentence in this story,
is utterly fascinating.

                      * * *

THE NEW YORK TIMES
June 23, 2000

Fossil Discovery Threatens Theory of Birds' Evolution
By JOHN NOBLE WILFORD
   
 
Scientists have discovered fossil evidence of the
oldest known feathered animal, a small reptile that
probably glided among the trees 75 million years
before the earliest known bird, and they say this
challenges the widely held theory that birds evolved
from dinosaurs. 

The animal, Longisquama insignis, lived in Central
Asia 220 million years ago, not long after the time of
the first dinosaurs. It had four legs and what
appeared to be feathers on its body. From impressions
left in stone, its elongated back appendages had
hollow shafts and other characteristics closely
resembling those of feathers. 

"We can identify certain structures in these fossils
that you only find in feathers," said Terry D. Jones,
a member of the discovery team and the lead author of
a report being published today in the journal Science.
"So we're quite sure we're looking at the earliest
feather." 

Prior to this, the oldest feather belonged to
archaeopteryx, also recognized as the earliest bird.
Archaeopteryx lived about 145 million years ago, and
its fossils were found in Germany in the 19th century.
Scientists who analyzed the Longisquama fossils said
the animal had a wishbone virtually identical to
archaeopteryx and similar to modern birds. 

In the cautiously worded report of the new findings,
the scientists referred to the feathers as nonavian --
that is, not related to birds -- and said, "The exact
relationship of Longisquama to birds is uncertain." 

But in interviews and a news release by Oregon State
University in Corvallis, one of several universities
from which researchers were drawn, members of the
discovery team threw down the gauntlet in their
dispute with other paleontologists who favor a direct
evolutionary link between dinosaurs and birds. 

While the new fossil evidence does not conclusively
establish that Longisquama was an ancestor of flying
birds, John A. Ruben of Oregon State said, it would
have lived in the right time and had the right
physical structure to have been an ancestor -- and it
was clearly not a dinosaur. 

Moreover, he and other scientists noted, the advanced
development of the newly discovered feathers suggested
that feather evolution extended back much earlier,
probably before the first dinosaurs appeared on the
scene about 240 million years ago. 

Paleontologists have long agreed that birds evolved
from reptiles. 

Archaeopteryx itself is a blend of saurian and avian
traits. But were the bird ancestors dinosaurs or
another reptilian lineage? Beginning with research by
John Ostrom of Yale University in the 1970's, evidence
seemed to favor a dinosaurian heritage, though a few
scientists, Dr. Ruben among them, held out against the
emerging orthodoxy. 

Storrs Olson, an ornithologist at the Smithsonian
Institution who was not on the discovery team but has
been skeptical of the dinosaur-bird theory, agreed
with the interpretation of the fossils and the
implications for understanding bird evolution. 

"These extraordinary structures really can be only
feathers," Dr. Olson said. "It's extremely important,
more important than the discovery of archaeopteryx." 

Mark A. Norell, a paleontologist at the American
Museum of Natural History in New York and a leading
exponent of a dinosaurian ancestry of birds, said he
was not ready to concede that the fossil impressions
are of true feathers. 

"Even if these turn out to be feathers, they have not
established that Longisquama is ancestral to modern
birds," Dr. Norell said. 

The discovery ruffling paleontology's feathers was
made by scientists from the University of Kansas, the
Russian Academy of Sciences, the University of North
Carolina at Chapel Hill, the City University of New
York, the College of Charleston, Sonoma State
University in California, in addition to Oregon State.
Dr. Jones, who participated in the research as a
graduate student at Oregon State, is now on the
faculty of Stephen F. Austin State University in
Nacogdoches, Tex. 

The fossils in question were excavated in 1969 in
Kyrgyzstan, a former Soviet republic. When the
impressions now said to be feathers were first
identified as reptilian scales, the specimen was put
away in a drawer in Moscow and ignored. But they were
retrieved and displayed as part of a touring exhibit
of Russian fossils last year. Seeing them, Dr. Jones
and Dr. Ruben said they realized immediately that this
was a very old animal with feathers. 

Other paleontologists and ornithologists were called
in for a look. 

Alan Feduccia of the University of North Carolina,
author of "The Origin and Evolution of Birds" (Yale
University Press), was struck by the hollow shaft
covered by a sheath, a characteristic of bird
feathers. 

"This is a dramatic finding," Dr. Feduccia said.
"Everything about the feather points to aerodynamic
structure, indicating that the initial function of
feathers was in an aerodynamic context." 

A point of contention in the dinosaur-bird debate
centers on the initial function of feathers. Dinosaur
partisans argue that when some dinosaurs became
warm-blooded they developed down as insulation and
this led to feathers, which then gave them the ability
to fly. Their opponents contend that in some
coldblooded reptiles feathers evolved from their
scales and were adapted originally for flight. 

>From an examination of the Longisquama skeleton,
scientists inferred that its body feathers would have
been adequate for gliding but its musculature would
not have supported powered flight. Given more time,
though, the muscles could have developed and the
feathers could have spread to the forearms, creating
wings, the discovery team suggested. 

"A point that too many people always ignored is that
the most birdlike of the dinosaurs, such as
bambiraptor and velociraptor, lived 70 million years
after the earliest bird, archaeopteryx," Dr. Ruben
said in a university statement. "So you have birds
flying before the evolution of the first birdlike
dinosaurs. We now question very strongly whether there
were any feathered dinosaurs at all." 





=====
Larry

"I've been ionized, but I'm OK now."

http://members.tripod.com/~megalania/index.html

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