hello tweets,

Today's ornithology exam question:

Did flight in birds evolve

(a) when ground-dwellers ran, flapped, and lifted off?
(b) when tree-dwellers jumped, glided, and then flapped?
(c) when ground dwellers ran up into trees, flapping to help gain
traction?

more data, more discoveries and more discussion to follow!

today, the washington post published an article that summarizes how
birds evolved flight from ken dial's Science article, along with a
summary of the four-winged feathery dinosaur recently described in
Nature.

read on ....

regards,

Devorah A. N. Bennu, PhD
email:nyneve at amnh.org or nyneve at myUW.net
work page http://research.amnh.org/ornithology/personnel/bennu.htm
personal pages http://research.amnh.org/users/nyneve/

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http://www.washingtonpost.com/wp-dyn/articles/A30096-2003Jan22.html

New Species of Flying Dinosaur Found
Predator Lived in Trees, Likely Used Plumage to Glide

By Guy Gugliotta
Washington Post Staff Writer
Thursday, January 23, 2003; Page A03

Scientists have discovered a new species of flying dinosaur unlike any
seen before, a spectacular four-winged predator that lived in trees
and probably used its elaborate plumage to glide from branch to branch,
research published yesterday said.

The find, in northeastern China's fossil-rich Liaoning Province,
significantly boosts the "top-down" theory of the origin of flight:
that birds evolved from tree-dwelling dinosaurs that glided through
treetops before flapping their wings.

"This time the evidence is overwhelming," said paleontologist Xing Xu,
of China's Institute of Vertebrate Paleontology and Paleoanthropology.
"It's hard even to imagine how these little animals could have moved
around bipedally" -- on their hind legs. Xu led the six-member Chinese
team whose findings were reported yesterday in the journal Nature.

The team recovered six specimens of the small predatory raptor that
showed nearly complete skeletons as well as the sharply etched outlines
of elaborate feathers on the forelimbs, hind limbs and tail. Xu's team
called it a four-winged dinosaur -- the first ever found.

University of Kansas evolutionary ornithologist Richard Prum, whose
analysis accompanied the research report, called the Liaoning research
"the most exciting find on the question of the origin of flight" in the
140 years since the discovery of Archaeopteryx, the 150-million-year-old
fossil regarded as the world's first true bird.

But other scientists were reluctant to give the new, four-winged flyer
such exalted status. "It's important, certainly," said Brown University
vertebrate morphologist Stephen Gatesy. "The first reflex is to say that
this is a stage on the way to birds, but for all we know, this could be
a quirky side branch."

Regardless of the new dinosaur's ultimate destination in the
evolutionary tree, yesterday's report was the second major paper this
month on the origin of flight to shake up the century-old debate between
the top-down school and the "bottom-up" school, which holds that flight
developed among small, land-dwelling dinosaurs that learned to run and
flap their winged forelimbs until they achieved liftoff.

Last week University of Montana biologist Kenneth P. Dial proposed an
intermediate stage, reporting in the journal Science how seemingly
awkward, heavy-legged modern birds -- such as chickens or turkeys --
use their wings as airfoils to gain traction as they run up steep
inclines. Dial suggested that small, feathered dinosaurs may have used
the same technique to get up into trees.

The two papers "help show that the dichotomy between top-down and
bottom-up is false," said Ohio University evolutionary biologist
Lawrence Witmer. "These finds from China demonstrate that there are a
lot of tiny predatory dinosaurs" that likely had reason to want to get
off the ground. Although the majority appear to have been primarily
ground-dwellers, he added, "I don't see how you keep them out of the
trees."

The newly discovered animal measures about 30 inches from its head to
the tip of its long tail, but the body is about the size of a large
pigeon. It is a predatory carnivore belonging to the same dinosaur
group as Tyrannosaurus rex and the smaller raptors. Xu's team dubbed
the new discovery Microraptor gui.

The Xu team unearthed the specimens in the Liaoning fossil fields,
where an entire ecosystem appears to have been suddenly buried, perhaps
by volcanic ash, 130 million years ago.

Over the past few years, Liaoning has produced unprecedented discoveries
of fossils of small therapods that clearly show the outlines of
feathers. These animals, fast runners with "killer claws" on the second
digit of their hind limbs, were basically two-legged land-dwellers.
Bottom-up advocates theorize that these animals' weak forelimbs
eventually developed into wings as they made the evolutionary transition
to birds.

M. gui also has "killer claws," but its hind limbs contrast sharply with
those of most other small raptors, because -- like the forelimbs -- they
are thickly carpeted with functional feathers. Xu's team suggested the
plumage made it impossible for M. gui to be nimble on the ground.
Instead, the team theorized that it lived aloft, gliding among branches
like a tree squirrel. Witmer noted that even though M. gui is not as old
as Archaeopteryx, it could be a descendant of a shared ancestor.

"It has many of us scratching our heads," Witmer added. Although the new
discovery is the first documented flying -- or gliding -- raptor, the
feathered hind limbs almost certainly didn't "flap," and there is no
conclusive evidence on whether M. gui could splay its hind limbs in a
wing-like pose.

The hind limbs' heavy feathers may have been for "display purposes"
rather than flight, he added: "Animals will endure all kinds of deficits
in their lives if it gives them more and better mates," Witmer said.

Brown's Gatesy said, "What's so, so wonderful is that it's clear that
this is what it looked like. Now we have to figure out what it did. I
don't know what's going on with the rear end. We need somebody who knows
hips."

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