Prehistoric Gliding Lizard Discovered in U.S.
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 Virginia-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.)
"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 Vertebrate Paleontology.
Among the gliding reptiles that have previously been found from the Triassic era are two specimens called Icarosaurus and Kuehneosaurus, 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.)
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.
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."
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