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Photo: Prehistoric Gliding Lizard Discovered in U.S.  

Stefan Lovgren
for National Geographic News
June 12, 2007

Two hundred and twenty million years ago long-necked lizards spread their ribs and glided on winglike membranes through North American forests, according to a new discovery.

Two fossils of the animal, called Mecistotrachelos apeoros ("soaring, long-necked") were excavated at a quarry on the Virgina-North Carolina state border.

The lizard has a much longer neck than the few other gliding reptiles that have been found dating back to the Triassic period (about 250 to 200 million years ago).

 

(See a picture of another gliding reptile, from 144 million years ago.) ~ http://news.nationalgeographic.com/news/2007/03/070320-gliding-liza...

Photo in the News: Ancient Lizard Glided Using Its Ribs

"This is a very different form of gliding reptile from what we've seen before," said Nick Fraser, a vertebrate paleontologist at the Virginia Museum of Natural History who discovered the fossils.

The study is reported in the latest issue of the Journal of Vertevrate Paleontology.

 

Protorosaurs

 

Among the gliding reptiles that have previously been found from the Triassic era are two specimens called Icarosaurus andKuehneosaurus, which were found in New Jersey and the United Kingdom, respectively.

Like the newfound species, these animals had elongated ribs, which supported gliding membranes—similar to modern-day Draco lizards found in Southeast Asia. 

A third gliding reptile from the Triassic period is called Sharovipteryx (previously known as Podopteryx, or "foot wing").

Unlike the others, Sharovipteryx's main flight membrane was stretched between long back legs rather than its very short front limbs.

"We're not sure where [Mecistotrachelos apeoros] falls into things, but probably within a group of long-extinct reptiles called protorosaurs."

Protorosaurs were part of an order of diverse, predatory reptiles that lived as far back as 280 million years ago.

Study co-author Paul Olsen, a paleontologist at New York's Columbia University, sees the diversity of gliding mechanisms among prehistoric lizards as an indication of a golden age of species diversity.

The newfound form of lizard "wing," he said is "emblematic of our growing knowledge of land animal diversity during the Late Triassic.

"We now know the Late Triassic was a time of stunning diversity all to itself, a high point before the fall—the mass extinction near the Triassic-Jurassic boundary," Olsen said. 

The new study was partly funded by the National Geographic Society's Committee for Research and Exploration. (National Geographic News is part of the National Geographic Society.)

 

Flat Rock

 

Fraser found the first fossil back in 1994, but was unable to figure out what it represented because of its poor condition.

A second fossil, discovered by Fraser eight years later, faintly showed a tail and a neck. But the second fossil was also in too poor a condition to prepare.

Instead, the descriptions of the lizard had to be based entirely on CT scans performed at Pennsylvania State University.

Even that proved problematic.

The second fossil was "a strange object to CT scan because of its flat shape," said Tim Ryan, a research associate at Penn State's Center for Quantitative Imaging.

"CT scanners don't particularly like flat, oblong things. They much prefer cylindrical sorts of objects," Ryan added.

"It was a test of the scanner and our ingenuity that we were able to get decent data from it."

The scanning revealed the bones of the lizard, and the scientists were able to reconstruct what the animal looked like.

 

Robust Ribs

 

Study leader Fraser said the gliding lizard's elongated neck would seem to complicate its flying ability.

"The neck was about 2 inches [5 centimeters] long, which is really long given the [length] of the animal"—only about 10 or 11 inches (25 or 28 centimeters).

"Presumably it held its neck straight forward while gliding," Fraser added.

The lizard also had unusual feet, which were preserved curled up in a grasping posture.

"We think that tells us something about its lifestyle—that this was an arboreal animal that scurried up trees while foraging for insects on the way, before gliding onto neighboring trees," Fraser said.

Another interesting feature is that the first two to three of the animal's elongated ribs are very thick.

"If you are a glider, you want to keep your bone structure as light as possible, so it's quite unusual to have this thickened rib there," Fraser said.

"We think that it had pretty good musculature attached to those ribs … and that it had much more control over where it went than the other Triassic gliders."

 

FOR SOME VERY INTERESTING INFORMATION ON MODERN :FLYING DRAGONS" or "FLYING LIZARDS" VISIT THE DRACO VALONS (Common Flying Dragon) page at: http://totemtalk.ning.com/forum/topics/draco-volans-common-flying-d...

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Photo in the News: Ancient Lizard Glided Using Its Ribs ~ http://news.nationalgeographic.com/news/2007/03/070320-gliding-liza...

March 20, 2007—Bar food connoisseurs may now have a new mascot—an animal with wings made out of its ribs.

Researchers from China uncovered remarkably preserved remains of the unique creature—an ancient lizard that glided through the air on membranes supported by eight elongated ribs.

Named Xianglong zhaoi, the bizarre animal, as seen in this artist's recreation, lived in treetops during the early Cretaceous period, which began about 144 million years ago.

The animal's 6.1-inch-long (15.5-centimeter-long) skeleton (inset) was found in Liaoning province in northeastern China—complete with superbly preserved imprints of its patagium, or wing membranes. Fully extended, the patagium would have stretched about 4.5 inches (11 centimeters) across.

The animal might also have been surprisingly agile in the air, as its wing features "are close to those in fast-flying birds with great maneuverability," write the researchers in this week's edition of the journal Proceedings of the National Academies of Science. (Related: "Dino-Era Bird Flew With Four Wings, Study Says" [September 28, 2006].)

While many gliding creatures are known—including flying squirrels, frogs, and lemurs—the new creature represents the only gliding fossil lizard ever found, the researchers add.

Only two other creatures are known to use their ribs in a similar fashion—living lizards of the genus Draco in Southeast Asia and a lizardlike fossil creature from the late Triassic period, about 200 million years ago.

What's remarkable, the scientists say, is that all of these creatures developed their gliding abilities independently—a startling example of nature developing the same useful ability in unrelated species.

Photo: Dino-Era Bird Flew With Four Wings, Study Says

http://news.nationalgeographic.com/news/2006/09/060927-four-wings.html

September 28, 2006

Four wings were better than two for the earliest birds, which became airborne by spreading both their feathered arms and legs, a new study says.

The research suggests that the ancestors of modern-day birds first took to the skies by gliding down from trees.

This study is based on well-known fossils from Germany of Archaeopteryx, the most primitive known bird (related news: "Dinosaur-Era Bird Could Fly, Brain Study Says" [August 2004]).

The fossils were re-examined by paleontologist Nick Longrich from the University of Calgary in Canada, who found that the flying dinosaur's leg feathers have an aerodynamic structure and likely acted as lift-generating "winglets."

Longrich said that his research "puts forward some of the strongest evidence yet that birds descended from arboreal parachuters and gliders, similar to modern flying squirrels."

The study supports the "tree down" theory for the origins of avian flight.

This theory suggests that the immediate ancestors of birds were tree-dwelling dinosaurs that developed the ability to glide and paved the way for self-propelled flight.

The competing "ground up" hypothesis argues that species of terrestrial dinosaurs gave rise to birds by running at high speeds and evolving rudimentary wings that lifted them off the ground.

Stripped Fossil

Fossils of the dino-era bird Archaeopteryx,which lived some 150 million years ago, were first discovered in 1861. Eight further specimens were subsequently unearthed.

While researchers at the time noted feathers on the creature's hind limbs, these were generally thought to be used for insulation or display, not for flying.

Longrich examined the structure and function of Archaeopteryx's hind-limb plumage using the fossil record, including the so-called Berlin specimen.

Found in 1877 and now on display at the Museum of Natural History in Berlin, the fossil bird had unusually long feathers around its legs.

Some researchers broke ranks more than a century ago to suggest thatArchaeopteryx's leg feathers did play a role in flight.

But, Longrich says, the issue was later forgotten when much of the hind limb plumage of the Berlin specimen was destroyed.

"The specimen was prepared sometime in the late 19th or early 20th century," the paleontologist said. "Most of the hind limb feathers were removed from the right leg to expose the bones of the legs and pelvis."

All that remains of those feathers are photographs, a cast, and a counter slab of limestone bearing an imprint of the feathers.

"What remains of the plumage on the main slab is not nearly as impressive," Longrich added.

Still, closer analysis of the fossil revealed to Longrich that the feathers have features needed for flying, such as curved shafts and asymmetrical vanes, which would have acted as airfoils to help generate lift.

Writing in the current issue of the journalPaleobiology, Longrich notes that several living species use their hind legs as airfoils to glide from trees, including types of lizards and frogs.

The use of all four limbs while airborne is likewise seen in tree-dwelling animals such as flying squirrels (wallpaper: flying squirrel).

Setting the Stage

But, the researcher said, the main reasonArchaeopteryx was initially overlooked as a four-winged bird was because the idea seemed "just too improbable, too foreign."

"Everybody knows that birds don't have four wings, so we overlooked them even when they were right under our noses," he said.

That changed when several fossils of a new four-winged dinosaur were discovered in China in 2002, prompting researchers to reassess Archaeopteryx's leg feathers.

Chinese fossil experts suggested that the species, Microraptor gui, used its plumed limbs and a long, feather-fringed tail to glide between trees (read "Four-Winged Dinosaurs Found in China, Experts Announce" [January 2003]).

"I never would have considered the idea of four-winged birds," Longrich added.

"But after the Chinese four-winged dinosaurs shattered my preconceptions, I was willing to say, Why the heck not?"

Archaeopteryx may mark a transitional evolutionary stage between Microraptor-like dinosaurs and modern birds, Longrich says.

"The other possibility is that Archaeopteryx represents the ancestral condition," he added, with one branch of the family tree leading to advanced birds with reduced hind wings.

"The other branch—Microraptor and allies—went off in the other direction and evolved even larger hind wings."

The new study apparently undermines the "ground up" theory to explain the origins of bird flight.

"'Ground up' seems to be more popular these days," Longrich said. "I think the reasoning goes that birds descend from dinosaurs, dinosaurs were terrestrial, so birds must descend from terrestrial animals.

"However, a lot of people feel that an arboreal origin makes a lot more sense, and not all paleontologists are so quick to rule out the idea that birds could come from arboreal dinosaurs."

Joel Cracraft, curator of birds at the American Museum of Natural History in New York, said Longrich's research "will be studied and talked about in all discussions dealing with the evolution of avian flight."

He said the study "nails" the idea that Archaeopteryx had an airfoil on its hind limbs and agrees that it suggests the primitive bird was a good glider.

But, Cracraft added, "whether [the study] also nails the 'tree down' hypothesis is another matter, mainly because the dichotomy between 'tree down' and 'ground up' is too simplistic for my mind."

"Clearly components of flight evolved in [running] dinosaurs," he added. "Our knowledge should increase as more fossils are studied."

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