by Dave Yanko
EASTEND—People who study dinosaurs for a living have long debated
the feeding habits of the fearsome Tyrannosaurus Rex. Some palaeontologists
argue T.rex was a scavenger whose top-heavy weight and tiny forearms
made it impossible for him to pursue and capture live prey. Others
contend the formidable beast used his massive tale to provide balance
during the chase, and his awesome jaws to subdue supper.
In an article written for Pacific Discovery magazine, author Blake
Edgar says both sides would probably agree with the comic-strip
character Calvin, who addressed the issue in a report presented
to his classroom: "I say tyrannosaurs were predators, because it
would be so bogus if they just ate things that were already dead.
|Palaeontologist Tim Tokaryk
Royal Saskatchewan Museum palaeontologist Tim Tokaryk seems to enjoy the debate.
As the man who presides over two important T.rex discoveries, he
keeps track of it.
"There was a wonderful research project done recently that showed
that if T.rex was going at a certain speed and he tripped, his whole
face would have been crushed," says Tokaryk, who works out of the T.rex Discovery Centre in Eastend, Saskatchewan.
"He had nothing to prevent him from falling. And even though his
skull was extremely large, it was very pneumatic—filled with a
lot of holes for muscles and so on, and also as a weight-reducing
Lending heft to hunter theory, or so some proponents maintain,
is another recent study that employed a piston-powered mockup of
T.rex jaws and teeth to test the beast's 'jaw-clamp' power. The
device was used to puncture a cow pelvis in a way that mirrored
T.rex bite marks found on the fossilized pelvis of a Triceratops.
Triceratops had a bone density similar to that of a cow.
The tests revealed T.rex's canines endured a force of 1,440 pounds
to inflict the damage seen on the Triceratops bone. Teeth located
closer to T.rex's jaw joint could produce some 3,000 pounds of force,
or 'the weight of a pickup truck behind each tooth', as one of the
researchers put it. (A human jaw might muster 175 pounds of force
at the back molars.)
teeth were surprisingly tough.
That kind of power is consistent with an animal who hunted live
prey, say the study's authors. Scavengers wouldn't require such
bone-crushing force to tear flesh from an animal that couldn't escape.
Considering the jaw-clamp results, the discovery of a fossilized
T.rex dropping containing bone fragments from another dinosaur would
seem to support the notion T.rex hunted for a living. But Tokaryk,
who was involved in the unique find, says the fragments don't really
advance the debate one way or the other. That's because little is
known of the bones original owner, other than he was likely a juvenile
herbivore about the size of a cow or pony. No one can say whether
he was dead or alive.
"The (jaw-clamp study) shows that T.rex could shatter bone. And
what our specimen shows is that it did."
Tokaryk and a colleague in 1995 found the 44-by-16-cm (17-by-6-inch)
dropping, known as a 'coprolite', in the fossil-rich Frenchman Formation
around Eastend, in southwest Saskatchewan. Its discovery and associated
research spurred a host of creative headlines when they were announced
in the June, 1998 issue of the scientific journal Nature.
In spite of the scatological puns in the popular press, the find
is an important one.
It's the first coprolite that can be definitely identified as a
carnivorous dinosaur dropping. Moreover, Tokaryk and his American
research colleagues are almost sure it was deposited by a T.rex.
Sixty-five million years ago, in the area where it was discovered,
there were no other meat-eating creatures capable of producing such
large dung. Simple elimination, so to speak.
Beyond illustrating T.rex was capable of shattering bone, the coprolite
find contradicts the assumption carnivorous dinosaurs like T.rex
(and like today's crocodiles) completely dissolved bones during
dung was found while excavating another fossil site.
The discovery also has scientists excited about the prospect of learning
more of the internal workings of dinosaurs, as well as what might
be revealed of the environment in which they lived.
"The skeleton of a dinosaur doesn't usually express a moment in
time," says Tokaryk. "With a coprolite, you can easily infer a biological
moment in time: The creature was eating something, it defecated,
and here's the remains."
As for the hunter/scavenger question, Tokaryk can't imagine what
kind of evidence would end the debate.
Maybe if someone found preserved tracks that definitely belonged
to a T.rex, and they clearly showed he was chasing another creature,
palaeontologists could say with some degree of confidence he was
a hunter rather than a scavenger, he says. In the meantime, it's
anybody's guess. Here's Tokaryk's:
"In his time period, at the end of The Age of Dinosaurs, he was
the biggest thing around.
"If there was a free meal—as there is in nature all the time—I'm sure he would take it. And if there was a herd of duckbills
or Triceratops—including the sick and old—he'd likely go after
it. He could probably have short bursts of very fast speed, but
probably lose out after a certain distance."
No video at 11.
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