Dinosaur hunters finding new clues in those old bones (news story)

["bh480@scn.org" <bh480@scn.org>]

From: Ben Creisler bh480@scn.org
News story from:
http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Artic
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67

Dinosaur hunters finding new clues in those old bones
Scientists able to reconstruct lives of dinosaurs New technology is
changing the face 

of palaeontology
Apr. 8, 2006. 01:00 AM
PETER CALAMAI
SCIENCE WRITER


An arsenal of leading-edge technologies, combined with new thinking, is
helping scientists get up close and personal with dinosaurs.

The results, which have been trickling out over the last few years, are
transforming palaeontology from primarily a study of old bones into
reconstructing in detail the lives of dinosaurs, creatures that pushed the
limits of what is possible biologically.

Larry Witmer, a professor of anatomy at Ohio University, rhymed off a few
of the most intriguing dinosaur questions at the recent annual meeting of
the American Association for the Advancement of Science (AAAS) in St. Louis:

How did an animal weighing more than 50 tonnes support itself or pump blood
to a head 10 metres from the heart?

What brain power could dinosaurs muster to handle their relatively complex
lives?

What kind of metabolic fires had to burn just to keep these massive animals
active?

"We need to flesh out dinosaurs," Witmer said. "We need to see what the
bones can tell us about the soft tissues that clothe the animal." 

In some quarters, such talk immediately raises the spectre of using DNA
from dinosaurs to produce living clones of the creatures that ruled the
world 65 million years ago, an idea popularized in the Jurassic Park movies.

Most experts scoff at the idea of dinosaur parks. If some dinosaur DNA were
found, they say, it's likely to be so badly fragmented that reconstructing
a complete dinosaur genome would be impossible. Even with that elusive
genome, there's the further challenge of finding a modern animal whose egg
could successfully grow a dinosaur embryo.

And why bother wasting time on such science fiction, when the real dinosaur
science is so fascinating?


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`T. rex certainly couldn't dance, and if it jumped, it would only be once'

Jack Horner, fossil hunter

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For example, Witmer's lab has mapped the insides of skulls of more than 100
dinosaurs with the kind of CT-scanning techniques used in hospitals (making
traditional plaster casts might damage the fragile fossils). The
researchers then employ 3-D visualization to build a computerized mould of
the inside of the skull cavities.

>From this virtual scan, Witmer reconstructs sections of the dinosaur
brains, which allows him to figure out things like brain size, the
mechanics of the olfactory system and the workings of the inner ear. In
turn, this information is providing new insights into how dinosaurs used
their senses to thwart predators, attract mates and find food.

Witmer's first breakthrough came several years ago with the revelation that
dinosaur noses had long been drawn in the wrong place, high on the forehead
and far back in the nasal cavity. The CT scans demonstrated, however, that
dinosaur nostrils were actually much further forward in the snout and down
low near the animal's upper lip, much like most vertebrates today. 

Now, Witmer has reconstructed the complete smelling pathway for both the
carnivore Tyrannosaurus rex and diplodocus, the family of long-necked
herbivores. He combined this with findings about the hearing apparatus in
both dinosaurs and their respective brain sizes. (T. rex's brain cavity was
seven times larger than diplodocus'.)

The conclusion? Most sensory capabilities of diplodocus were modest, except
for smell. The herbivore's sense of smell was at maximum when the head was
pointing downward in the feeding position.

By contrast, T. rex had an ear adapted to picking up the faint sounds of
potential prey and a refined sense of balance that permitted rapid
swivelling of the head and neck. Its senses were most alert with its head
held high.

Witmer told reporters in St. Louis: "I'm still amazed at how much
biologically relevant information we can tease out of these old bones."
There's one piece of information which no one even suspected could be
teased out, until palaeontologist Mary Higby Schweitzer capitalized on the
ultimate in lucky breaks.

That happened during a 2000 collecting foray led by legendary fossil-hunter
Jack Horner at Hell's Creek, a dinosaur graveyard in the Montana badlands.
Horner's team gathered more T. rex bones than a helicopter could take in a
single load. Reluctantly, they broke open the protective plastic jacket, in
the process splitting a metre-long T. rex femur, which shed some bone
fragments.

Wrapped in tin foil, those fossilized bone chips from a T. rex called Bob
were shipped to Schweitzer, a former Horner student, who had just set up a
lab at North Carolina State University. The lab was concentrating on a new
discipline Schweitzer pioneered, a union of molecular biology and
palaeontology that relies on finding living tissue in fossils tens of
millions of years old.

When Schweitzer looked at the bone fragments, she knew two things at once:
Bob was a female and she was pregnant when she died.


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`We need to see what the bones can tell us about the soft tissues that
clothe the animal'

Larry Witmer, anatomy professor,

Ohio University

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Trained as a biologist, Schweitzer had spotted the telltale texture inside
the femur of medullary bone, a type of tissue that grows only inside the
long bones of female birds to temporarily store calcium needed for egg
production. For the first time ever, scientists could definitively
determine the sex of a dinosaur.

But the surprises didn't stop there, as Schweitzer told the AAAS meeting.
Two years ago, she asked her lab assistant to do the unthinkable: soak bits
of the T. rex medullary bone in a mineral-eating acid.

"Nobody dissolves away the minerals as I did because the conventional
wisdom is that you'd be left with nothing," she said.

What Schweitzer was left with, however, turned out to be the organic part
of the dinosaur bone, soft tissues mostly composed of collagen fibres that
everyone long assumed wouldn't last more than a few dozen years, much less
68 million. Soon afterward, her lab also identified osteocytes, the cells
found inside living bone.

Since then Schweitzer has found collagen and osteocytes in bones from a
wide range of animals ? ostriches dead less than a year, a 1,200-year-old
moa (an extinct New Zealand bird) and a woolly mammoth that perished
300,000 years ago.

If this discovery continues to check out ? and there have been skeptics ?
it could allow scientists to learn much more about the biology of
dinosaurs, possibly including what diseases might have afflicted those
giants.

At the Museum of the Rockies in Bozeman, Mont., Horner has already
identified one thing that would prove fatal to T. rex: jumping.

The doyen of American fossil-hunters, Horner practises what he calls
"destructive palaeontology," shaving off slices of precious dinosaur bones
thin enough to examine under a microscope.

"We can see all sorts of neat things," he said.

Those include growth rings, like trees, which count off a dinosaur's age.
As well, the sections contain holes where blood vessels passed along the
bone. These holes can take up two-fifths of the bone space when a dinosaur
is growing but settle back to one-fifth at maturity. Using this ratio, a
landmark paper by Horner concluded T. rex was fully grown in 20 years.

Studying the transparent slices also allowed Horner to determine that
Tyrannosaurus had a very rigid backbone much more like today's chicken than
a lizard.

"T. rex certainly couldn't dance, and if it jumped, it would only be once,"
Horner said.
Additional articles by Peter Calamai





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