"Amazing" Dino Fossil Found With Skin, Tissue in China
for National Geographic News
|January 16, 2008|
The fossil of a dinosaur with a flesh wound has been discovered in northeastern China, offering the most complete view to date of dinosaur skin, a scientist says.
The fossil is of a 130-million-year-old Psittacosaurus, or parrot lizard, a beaked reptile about the size of a pig that could walk on either two or four legs.
The animal died after suffering a wound from a predator—or was perhaps bitten by a scavenger after it died—exposing the inner skin structure, which was preserved for millions of years.
A recent study of the fossil identified what appeared to be tooth marks in the wound.
The research also suggests that some dinosaurs had thick, scaly skin like that of modern-day reptiles, refuting the theory that dinos had primitive feathers.
The findings were reported by Theagarten Lingham-Soliar of South Africa's University of KwaZulu-Natal in the current issue of the Proceedings of the Royal Society B.
Soft Tissue Preserved
Lingham-Soliar has identified what he says is fossilized surface skin as well as a cross-section of the thick layer below the surface, called the dermis, around the animal's lower left side.
"To have soft tissue preserved is amazing in the fossil record, because clearly the soft tissue is about the first thing that will decay and disintegrate," Lingham-Soliar said.
"Until now we had seen only surface preservations, but this is the first time we see a deep cross-section of the skin cut away at right angles to the surface."
(Read related story: "'Dinosaur Mummy' Found; Has Intact Skin, Tissue" [December 3, 2007].)
The fossil was found in a formation in northeast China's Liaoning Province dating to between 125 million and 135 million years ago.
The area has yielded so many fossil discoveries in recent years that scientists have been unable to keep pace with them all. (Learn more about China's extraordinary fossil site.)
The excellent preservation of the newfound Psittacosaurus may have been a consequence of rapid burial and speedy mineralization of the soft tissue before it began to decompose, Lingham-Soliar said.
The animal's skin was at least 0.8 inch (2 centimeters) thick, with some 40 layers of a fibrous protein called collagen, making it ideal for defense against predators, Lingham-Soliar said.
But the thick skin was still able to stretch and flex to accommodate swelling in the belly from a heavy diet of plants and fibers, he added.
"[Lingham-Soliar] has been able to show more detail of the complex organization of the dermis—this implies that Psittacosaurus at least had a tough yet presumably flexible skin," said Paul Maderson, a retired evolutionary biologist at the City University of New York.
Alan Feduccia, an evolutionary biologist the University of North Carolina, agreed.
"It's very important in the sense that it's our first glimpse into the microstructure of dinosaur skin, and what he's shown is that it has multiple layers of collagen fibers," said Feduccia, who specializes in bird evolution.
"That's not unexpected, by the way, since that's more or less the pattern with reptilians' skin, especially thick-skinned reptiles."
Birds and Dinosaurs?
The finding could also cast further doubt on a theory that had gained many proponents in recent years—the possibility that dinosaurs had primitive feathers, suggesting that some are the ancestors of today's birds.
Lingham-Soliar argues that the parrot lizard was adorned with bristles of collagen fibers, not early feathers.
"What is unexpected is the 40-plus layers of collagen, which even in thinner-skinned meat-eating dinosaurs would comprise many layers of fibers with the potential of being misidentified as proto-feathers," Lingham-Soliar said.
But not all paleontologists agree with his conclusion.
Hans-Dieter Sues is associate director for research and collections at the Smithsonian National Museum of Natural History in Washington, D.C.
He said there is a "preponderance of evidence to support that birds came from dinosaurs" known as theropods.
"[Lingham-Soliar] has tried for some time to argue that the featherlike structures on the theropod dinosaurs from the same formation as [where] the Psittacosaurus [was found] are collagen fibers, too," Sues said.
"However, many of the Chinese theropods have complex structures that clearly cannot be explained away in that fashion."
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