What has four wings and . . .
http://www.startribune.com/stories/484/3608083.html
Robert Lee Hotz

Los Angeles Times



Published Jan. 23, 2003
                                                              DINO23
                                                                   


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Chinese researchers announced Wednesday the discovery of a
feathered dinosaur that glided on four wings - a diminutive
plumed dragon that could be a long-sought evolutionary link
between dinosaurs and the first true birds.
As remains of nature's earliest experiments with avian flight, they
rank among the most important fossil finds of the past century,
several experts on avian evolution said. They reveal the distant
past as a foreign country in which creatures soared on four wings,
not two, and predators prowled in pelts of down.
The curled and crushed skeletons of Microraptor gui, as the new
creature is named, preserve clear impressions of long
aerodynamic feathers. The feathers form airfoils
along spindly arms and legs in what appear to be
both forewings and hind-wings. The dinosaur also
has a long feather-fringed tail.
{PRIVATE "TYPE=PICT;ALT="}Four-winged
dinosaur



Associated Press

The new discovery lends weight to the idea that
feathered flight began with creatures like these
flapping between the treetops of ancient forests, not
with small downy dinosaurs skittering along the ground as many
other experts have theorized.
``It's an incredible discovery, the kind of thing that we've wished
for, well, for centuries now,'' said paleobiologist Kevin Padian at
the University of California at Berkeley who studies the origins of
flight.
Luis Chiappe, an expert on avian evolution at the Los Angeles
County Museum of Natural History who has examined the fossils,
pronounced the creature ``the winged Mercury of the dinosaur
world,'' referring to the divine messenger of myth who had wings
on his feet.
So far the researchers, whose finding are being published
Thursday in the journal Nature, have found six relatively complete
skeletons of these creatures, all unearthed from deposits of
volcanic and sedimentary rock in northwest China's Liaoning
province.
In all six specimens, the body of the dinosaur is covered with
inch-long feathers. The wing feathers are almost 5 inches long,
with vanes that resemble modern flight feathers. Such long
feathers around the feet would make it hard for the animal to run
on the ground, the researchers said, lending credence to the idea it
was a tree-dweller.
Just over 2 1/2-feet long, the four-winged Microraptor lived in
China around 130 million years ago, about 20 million years after
the appearance of Archaeopteryx, a two-winged flier considered
by many to be the first bird.
The aerial Microraptor itself may have lived after the first bird
evolved but it belongs to a much older family of small feathered
predatory dinosaurs that predate the origin of birds, said
ornithologist Richard Prum at the University of Kansas in
Lawrence. Its distinctive wings, like its feathers, are holdovers
from an earlier day.
The newly discovered dinosaur ``takes a critical position in the
evolution of flight,'' said paleontologist Xing Xu of the Institute of
Vertebrate Paleontology and Paleoanthropology in Beijing, who
led the team that analyzed the finds.
``We now know the closest relatives of birds have four wings and
live in trees.'' Xu said.
The fossils were found at two sites about 20 miles apart near the
town of Chaoyang in Liaoning province.
Xu and his colleagues excavated one skeleton in 2001 and
purchased four others from local farmers who regularly comb the
bone beds for new specimens. The sixth specimen was purchased
by Tianjin Museum of Natural History last year.
In the past five years, these deposits have yielded a steady stream
of unusually well-preserved fossils of unique dinosaurs and at
least one embarrassing forgery of a purported missing link
between dinosaurs and birds.
The researchers took care to test the authenticity of the
Microraptor fossils. Xu and his colleagues submitted the new
finds to computerized X-ray analysis and assured themselves the
fossilized skeletons were genuine.
Many of the previous finds - including the first examples of
feathered dinosaurs and the earliest known flowering plant -
forced scientists around the world to rewrite the book of life. In
the same way, the newest fossils to emerge from Liaoning will
require scientists to reconsider much of they had taken for granted
about how birds first took wing.
``These are weird animals,'' said paleontologist Mark Norell at the
American Museum of Natural History in New York. ``We can
create lots of scenarios about what was going on with them but
they require tests - computer simulations, models, aerodynamic
studies - to pin it down.''
The kinship of birds and dinosaurs was a radical notion not so
many years ago, but today is conventional wisdom. Even so, no
one is sure just how they first took to the air.
Just as feathers came before birds, so perhaps did true wings and
some form of primitive avian flight. The Microraptor discovery
``suggests the dinosaurian ancestor of birds first learned to glide
by taking advantage of gravity before flapping flight was acquired
in birds,'' Xu said. ``Four wings might make gliding easier.''
While enthusiastic about the discovery, several other experts
questioned the biomechanics of the creature's shoulder sockets,
hip joints and limbs. Do they fit together in a way that could have
allowed the animal to move its feathered limbs as wings?
Even if it could glide effectively, there is no reason to assume that
ability led directly to the evolution of flight in birds, experts said.
It is too soon to know whether these creatures truly flapped their
wings, soared, glided, parachuted or flew in some other as yet
undetermined mode. Multiple sets of wings could have been fairly
common - or, just as easily, an evolutionary dead-end.
``Was this one really on the direct line of bird evolution or was it
a side branch, something that evolved those peculiar feathers?''
Chiappe asked. ``Evolution was experimenting with many
designs.''
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