AUSTIN, TexasIn an article published in the March 29 issue of the scientific journal Nature, Dr. Timothy B. Rowe of The University of Texas at Austin department of geological sciences discusses his research into a fossil earlier claimed to be the "missing link" between birds and dinosaurs.
The fossil, dubbed "Archaeoraptor liaoningensis" became a subject of controversy after its photograph appeared in the November 1999 issue of National Geographic Magazine with a report saying the fossil was "perhaps the best evidence since Archaeopteryx that birds did, in fact, evolve from certain types of carnivorous dinosaurs." The magazine later published a retraction.
Rowe's analysis using UT Austin's High-Resolution X-ray Computed Tomography (CT) scanner facility revealed that the fossil was actually a composite of the tail of a new species of non-flying dinosaur and the skeleton of a primitive bird species also completely new to science.
Rowe is the director of the Vertebrate Paleontology Lab of UT Austin's Texas Memorial Museum of Science and History and is the J. Nalle Gregory Regents Professor in Geological Sciences. UT Austin co-authors include Dr. Richard A. Ketcham, a research scientist, and Dr. Matthew Colbert, a research associate, both in the department of geological sciences; and Dr. Cambria Denison, formerly of the Vertebrate Paleontology Lab. Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Bejing, China, and Dr. Philip J. Currie of Canada's Royal Tyrrell Museum of Paleontology in Drumheller, Alberta, also are co-authors.
UT Austin's CT scanner, the first of its kind in an academic setting, is similar to a conventional medical CAT scanner but has higher power and higher magnification. Its X-rays scan a specimen in slices or planes, creating cross section data. In other words, it allows researchers to inspect the insides of solid objects without destroying them. After the digital slices are processed, an analyst can view them as cross sections on a computer screen and build a 3-D image.
Rowe said analysis of the CT scans revealed evidence of air bubbles and "many nonverifiable fits between sides of the fractures What we found is that the specimen was built in three layers, and that many of the bone-bearing pieces were not lying in natural positions relative to each other. It's a mosaic."
The fossil in question reportedly had been discovered in Liaoning, China, in an Early Cretaceous bed of rock where a number of authentic fossils linking birds and non-flying dinosaurs have been unearthed. Like legitimate Archaeopteryx fossils, the so-called "Archaeoraptor" appeared to have both feathers and teeth. At first glance, its wings appeared to be more flight-capable than Archaeopteryx, the earliest known bird.
"Computed tomography alone cannot reveal differences between genuine and fraudulent mistakes, but it does provide numerous criteria by which to evaluate whether pairs of adjacent pieces lie in natural relation to one another," Rowe explained.
The analysis showed the fossil "was assembled from at least two, and possibly five, separate specimens." Interestingly, at least two of the specimens were entirely new to science and were nearly lost to researchers as a result of the incident, Rowe said.
Rowe said the positive side to the story is that "when fakes like this are perpetrated, we've got a way of finding out. We can scan them and verify them. In cases like this, we can say which parts of it are real, and if any deserve to be studied scientifically."
More CT scanning facilities are needed, said Rowe, and more individuals are needed to learn to operate the scanner and skillfully analyze data. Only two people at UT Austin are proficient scanner operators, and only about a dozen UT Austin faculty and two dozen students can process and analyze data, Rowe said. Plans are under way at two other universities to build CT scanners based on UT Austin's model, one in Pennsylvania and one in Tokyo, Japan.
For more information, contact Dr. Tim Rowe at (512) 471-1725 or (512) 232-5512 or Caroline Ladhani at (512) 232-1075. Additional information is available at <www.ctlab.geo.utexas.edu>.