Raleigh, NC (04/29/05) - Soft, pliable tissue has been discovered in the remains of dinosaurs, and the finding could revolutionize not only what is known about dinosaur biology, but how these ancient creatures are studied.
The tissue was found in remains of a 68.5 million year old Tyrannosaurus
Rex that was buried in sandstone in the Hell Creek Formation, Montana.
A description of the discovery was published in Science by Mary Schweitzer,
PhD, assistant professor of biology at North Carolina University.
Since the initial discovery, soft tissue has been found in remains from three additional dinosaurs, Dr. Schweitzer told Access Excellence in an interview. Her area of specialty is molecular paleontology, an area that uses various microscopic and analytical techniques to study the structure and composition of ancient remains.
Her work builds on findings that date back to the 1960s when Polish researcher, Roman Pawlicki, found evidence of preservation of three-dimensional structures that looked like cells in dinosaur remains. "What we did was verify and validate his findings and took them further," Dr. Schweitzer said.
Using chemical treatments to remove mineral deposits from T. Rex bone fragments, Dr. Schweitzer found something amazing: stretchy soft tissue that, when put under a microscope, looked like it contained blood vessels and other structures. The Science paper adds that the vessels "contain small round microstructures that vary from deep red to dark brown," but does not speculate on what exactly these might be.
At this point, it's hard to say why the material didn't degrade. It could have something to do with the fact the tissue was protected inside the bone structure, or how the dinosaur specimens were preserved, the type of fossilization that occurred in the region, or a mix of reasons. Dr. Schweitzer's team is continuing research to help answer some of the questions about preservation, and to learn more about the tissue. She explains that at this very early point, there is some uncertainty as to just what the soft tissue is.
While it certainly comes from dinosaur bone and looks like original material, whether bits of original molecules remain can only be shown with more tests. "Another possibility is the original material may have combined with environmental components to result in a chemical 'gamish' of material that is only morphologically similar to the starting material," she said. Either way, the discovery is significant. It will change what is known about the preservation of tissue over long periods of time, and may shed light on the biology of dinosaurs.
In the Science paper, the researchers compared the microscopic tissue samples to ones from a modern day ostrich. It was found that ostrich vessels and their contents were morphologically similar to those of the T. Rex's. Under a scanning electron microscope features in the ostrich and T. Rex vessels were virtually indistinguishable "suggesting a common origin," the article states. In future, studies of soft tissue from dinosaur remains will provide more clues about the links between dinosaurs and modern-day species.
Looking at Big Things in Small Ways
For a long time, very little was known about dinosaur biology, said Phil Currie, PhD, from the Royal Tyrrell Museum in Drumheller, Alberta, Canada. Researchers used to look just at big things, but now we are "looking more under microscopes and scanning electron microscopes, or doing geochemical or biochemical work," he said.
Starting about 25 years ago, the more geological approach to dinosaur studies switched to a more biological one, he said. Much has been learned about how dinosaurs walked, their family life, what they ate, how they reproduced and more. Over the past two decades, fossil records have yielded remains of feathers, color patterns, dinosaur embryonic soft tissue and more. That they survived this length of time has to do with the fact bacterial action stopped, and the tissue wasn't fully degraded, he said.
Not all dinosaur fossilization happens the same way. To have actual dinosaur tissue preserved, "all you have to do, really, is find the right kinds of circumstances where the bacterial action was stopped or didn't have a chance to react," Dr. Currie said. He was not involved in Dr. Schweitzer's work.
The finding of soft tissue vessels means "we have to start looking at almost all our specimens in a very different way because it shows these kinds of things can be preserved. Consequently, the limitations are not so much on the material, but on our own thinking about these things," Dr. Currie said.
Old Proteins in Mummies
In the unrelated field of paleoanthropology, researchers have been examining tissue samples that have survived for many thousands of years in mummies. It was only last year researchers from the University of Minnesota reported on the findings from DNA fragments that were extracted from 9,000 year old mummies from Chile and Peru. The fragments show that people living about 7050 B.C. had been infected with Chagas disease, and that the disease has persisted throughout the ages.
While thousands of years pale in comparison to the millions of years dinosaur fossils have been around, it does show that under the right conditions, certain soft tissue materials can persist for at least a few millennia. More work needs to be done to determine what parts persists in the much older dinosaur remains.The study was published in the Proceedings of the National Academy of Science (PNAS) by Arthur Aufderheide and colleagues.
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