[escepticos] teoría de los pajaritos pitos pitos...

["Javier Armentia" <planetario@...>]

Remito en ingles lo que me ha llegado:
De: Yves Barbero <ybarbero en yvesbarbero.com>
Enviado: viernes 23 de junio de 2000 11:02
Asunto: NY 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."
>
>
>
>
>
>
> --
> Regards,
>
> -Yves Barbero
>
>
>   e-mail:     ybarbero en yvesbarbero.com
> Web Site:     http://www.yvesbarbero.com
>