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Sabertooth Tigers And "Vertebrate Analyzer", A CAD Package

hmmm. sauropod necks anyone?


BUFFALO, N.Y. -- Cringe. That's what most people do when they look at
fossils of the impressive, eight-inch-long canines of the now extinct
sabertooth tiger, Smilodon fatalis.

But Frank Mendel, a University at Buffalo anatomist, sees those big teeth
and thinks: How in the world did they use those fangs?

A team of design engineers in UB's New York State Center for Engineering
Design and Industrial Innovation (NYSCEDII) is developing the first
interactive, computational toolkit designed to answer Mendel's question --
and others like it concerning how ancient beasts behaved -- with
mathematical precision.

"We are creating a computer-aided design (CAD) system for living things,"
said Mendel, Ph.D., associate professor of pathology and anatomical
sciences in UB's School of Medicine and Biomedical Sciences.

CAD allows engineers to develop three-dimensional models of buildings,
automobiles, airplanes or other complex systems on computers, but until
now it hasn't been applied to living organisms.

The objective of the Vertebrate Analyzer, as the CAD system is called, is
to create, mechanically articulate and animate skeletal models, "fleshing"
them with anatomically and physiologically correct "virtual tissues" that
respond according to their own biomechanical capacities and limitations.

"The hope is to build very accurate models so that we can better
understand the relationships among form (anatomy), function (physiology)
and behavior," explained Mendel. 
"The point of the toolkit is to be able to experiment with the form and
function of animals," explained Kevin Hulme, Ph.D., NYSCEDII's research
associate for engineering design and lead visualization scientist of the
center's Vertebrate Analyzer research team. "We want to provide users with
the freedom to add their own functions and modify existing features."

That versatility, they say, eventually could have significant potential
for medical and dental applications. From paleontologists who want to
build a virtual jaw of Tyrannosaurus rex to doctors who want to study what
happens to bones and ligaments in the human knee or to the TMJ
(temporomandibular) joint after injury, the ultimate potential of the
Vertebrate Analyzer is enormous, its creators say.

For evolutionary biologists, the Vertebrate Analyzer is designed to allow
them to do what has never before been possible: to "experiment" with
extinct mammals, from sabertooth cats to dinosaurs, potentially solving
some of the biggest questions remaining about ancient beasts. 
"One of the great things about the VA is its potential to emulate almost
anything," added Mendel. "We expect it to be capable of helping
researchers determine, for example, if the T. rex could, indeed, have
bitten through the armor plate of a duckbill dinosaur. We have chunks of
duckbill skin, so we should be able to characterize it and see if the
teeth of T. rex could have penetrated it without breaking."

To test Mendel's own hypothesis that Smilodon's fangs were used to cut the
throats of prey, rather than suffocate them as modern cats do, the
Vertebrate Analyzer team first must move briefly out of the virtual world
and into the real world.

This spring, members of the VA team with expertise in robotics will build
mechanical models of Smilodon and modern-day tiger skulls, complete with
hydraulic jaws and fangs of aluminum or dental materials in order to
choreograph attacks on horse, bison or cow carcasses.

"Using parts of fresh carcasses, which we will buy from local butchers, we
can recreate the biting process and calibrate our virtual models with real
numbers," explained Mendel.

Once the biting experiment is done, the carcasses will be dissected,
providing the UB team with the precise data on the minimum forces the
Smilodon would have had to generate to overcome the resistance offered by
the tissues of the prey's neck. 

So far, the group has assembled virtual models of the jaws and skulls of
a human, a lion, a tiger and a Smilodon.
At that point, the digital data then were "loaded" into the Vertebrate

The user then inputs information on the geometry of the muscles involved,
such as their length and diameter, as well as the physical structure of
the muscles and fibers, such as limits on tension and compression, if
known, and material strength.

"When this step is complete, the user simply points and clicks on the
model to attach the muscles to it," explained Hulme, "allowing the user to
perform many trial scenarios quickly and easily."

The VA toolkit allows users to navigate (i.e., rotate, translate and zoom)
around the model with a conventional PC mouse and keyboard. A perimeter
display window shows data on model fidelity, jaw angle, collision
properties and attached muscle characteristics.