Jeg vil tro at følgende artikel, taget fra:
http://nytimes.com/2005/03/25/science/25dino.html?ei=5094&en=47515d1d721
87617&hp=&ex=1111813200&partner=homepage&pagewanted=print&position=
vil have en vis interesse i denne gruppe. Specielt skulle mikroskopiske
undersøgelser af blodkar vise, at Tyrannosaurus rex mest af alt minder
om en - struds:
March 25, 2005
Dinosaur Find Takes Scientists Beyond Bones
By JOHN NOBLE WILFORD
Alive as dinosaurs may seem to children, knowledge of them as living
creatures is limited almost entirely to what can be learned from bones
that have long since turned to stony fossils. Their soft tissues, when
rarely recovered, have lost their original revealing form.
But now a 70-million-year-old Tyrannosaurus rex discovered in Montana
has apparently yielded the improbable, scientists reported yesterday:
soft tissues, including blood vessels and possibly cells lining them,
that "retain some of their original flexibility, elasticity and
resilience."
Moreover, an examination with a scanning electron microscope showed the
dinosaur's blood vessels to be "virtually indistinguishable" from those
recovered from ostrich bones. The ostrich is today's largest bird, and
many paleontologists think birds are living descendants of some
dinosaurs.
In a paper being published today in the journal Science, the discovery
team said the remarkable preservation of the tissue might open up
"avenues for studying dinosaur physiology and perhaps some aspects of
their biochemistry." Speaking at a teleconference, the team leader, Dr.
Mary H. Schweitzer of North Carolina State University, said, "Tissue
preservation of this extent, where you still have this flexibility and
transparency, has never been noted in a dinosaur before."
Dr. Schweitzer, as well as scientists not connected with the research,
cautioned that further analysis of the specimens was required before
they could be sure the tissues had indeed survived largely unaltered.
They said the extraction of DNA for studies of dinosaur genetics and for
cloning experiments was only a long shot, though at least reasonably
possible.
In a separate article in Science, Dr. Lawrence M. Witmer, an Ohio
University paleontologist who had no part in the research, said: "If we
have tissues that are not fossilized, then we can potentially extract
DNA. It's very exciting."
If the tissues are as well preserved as they seem, the scientists hold
out some hope of recovering intact proteins, which are less fragile and
more abundant than DNA. Proteins might provide clues to the evolutionary
relationship of dinosaurs to other animals and possibly help solve the
puzzle of dinosaur physiology: whether, as argued, dinosaurs were unlike
other reptiles in being warmblooded.
"If we can isolate certain proteins, then perhaps we can address the
issue of the physiology of dinosaurs," said Dr. Schweitzer, a biologist
affiliated with Montana State University as well as North Carolina
State.
Excavations of dinosaur remains sometimes turn up preserved tissues
other than bone, including feathers, embryonic fragments and internal
organs. But as Dr. Schweitzer's group noted, while in these cases their
shapes may be preserved, their original composition has not survived "as
still soft, pliable tissues."
It is usually difficult to determine what such modified tissues were
like in life when fossils are more than a few million years old. The
last of the dinosaurs died out 65 million years ago.
The T. rex with the soft tissue was found in 2003 by a fossil-hunting
team led by John R. Horner, a paleontologist with the Museum of the
Rockies at Montana State . Mr. Horner is a co-author of the journal
report, along with Jennifer L. Wittmeyer of North Carolina State and Dr.
Jan K. Toporski of the Carnegie Institution of Washington.
The trials of fieldwork led to the discovery of soft tissue inside a
thighbone.
Scientists cannot be sure why the tissues survived as they did, though
the protection afforded by the bone was almost certainly one factor.
Another may have been the possibility that the animal was buried in a
virtually oxygen-free environment very soon after death.
Geologically, the T. rex skeleton was excavated from the Hell Creek
Formation, in sandstone laid down about 70 million years ago.
Geographically, this was deep in a remote corner of the Charles M.
Russell National Wildlife Refuge, in Montana. The only way to get the
heavy fossils out was by helicopter.
Tyrannosaurs were famously huge predators. This one, estimated to have
been 18 years old at death, was not as large as most. Its femur, or
thighbone, was three and a half feet long; some T. rex femurs are at
least a foot longer. But the creature was large enough so that some of
the rock-encased long bones had to be broken in half to fit a helicopter
rig - not something paleontologists like to do.
At a laboratory in Bozeman, scientists inspected the broken thighbone
before anyone had a chance to apply preserving chemicals, which would
have contaminated the specimen. Dr. Schweitzer and colleagues noticed
unusual tissue fragments lining the marrow cavity inside the dense bone.
Fossilization had not been complete.
When fossilizing mineral deposits in the tissues were dissolved by a
weak acid, the scientists were left with stretchy material threaded with
what looked like tiny blood vessels. Further examination revealed
reddish-brown dots that the scientists said looked like the nuclei of
cells lining the blood vessels.
Copyright 2005 The New York Times Company
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Per Erik Rønne