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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
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
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)