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Many Dino Fossils Could Have Soft Tissue Inside


Scott Norris in St. Louis, Missouri for National Geographic News
February 22, 2006

Soft-tissue dinosaur remains, first reported last year in a discovery that shocked the paleontological community, may not be all that rare, experts say.

A 2005 paper in the journal Science described what appeared to be flexible blood vessels, cells, and collagen-like bone matrix from fossils of a 70-million-year-old Tyrannosaurus rex.

Mary Schweitzer, the North Carolina State University paleontologist who announced the finding, said her team has now repeated that feat with more than a dozen other dinosaur specimens.

To make sense of the surprising discovery, scientists are beginning to rethink a long-standing model of how the fossilization process works.

Schweitzer gave an update of her team's progress unraveling this mystery last Friday at the annual meeting of the American Association for the Advancement of Science, held this year in St. Louis, Missouri.

Traditional ideas of how fossils form do not allow for the preservation of soft, perishable organic tissues.

"We propose now that soft-tissue components of bone might persist in a lot more different animals, in a lot more ages and environments, than we once thought," Schweitzer said.
Until now, Schweitzer said, "the standard wisdom was that if you dissolve away the mineral [in fossils], there would be nothing left." That has been the case in about half of the specimens she has examined.

But the other half have yielded remarkably consistent results.

The same features have emerged, and they are virtually indistinguishable from tissue samples from modern species.

A 300,000-year-old wooly mammoth fossil, for example, yielded flexible vessels containing what seem to be red blood cells that lack nuclei, like those of modern mammals.

The dinosaur remains include blood cell-like structures containing nuclei, like those of birds today.
Schweitzer said a central focus of her research is to explain this phenomenon, which was once thought to be impossible.

New findingsnot yet publishedhave led her to suggest one possible explanation. The key, she believes, may be the iron content of the blood and muscle proteins hemoglobin and myoglobin.

After an organism dies, iron released from these proteins as they degrade may trigger the formation of highly reactive forms of oxygen known as free radicals. Other heavy metals in the environment may produce the same effect.

Schweitzer thinks these metal-generated free radicals may trigger the formation of longer molecular chains, known as polymers, which essentially bind and lock remaining cellular structures in place.

"Eventually, the polymerized remains become inert, free from attack from the outside and further chemical change," Schweitzer said.

The researchers are now trying to obtain a pure sample of the blood cell-like structures. If successful, Schweitzer hopes to apply a technique known as Raman spectroscopy to search for the presence of hemoglobin.

(follow the link for more, including a section on Peggy Ostrom of Michigan State and protein recovery)