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How to 'print out' a lizard head

Timothy Rowe has been carrying the head of a rare lizard around in his pocket for months now.

Well, it’s not a real head of Lanthanotus borneensis, but a bronze replica. Rowe, a geology professor at the University
of Texas at Austin, “printed it out” using a ThermoJet solid object printer that rendered a digital version of the lizard head into a wax model, which he cast in bronze. The digital version came from ta high-resolution CT (computer tomography) scanner run by the university’s department of geology and used by researchers from all over the world. The scanner is a high-resolution version of a medical CAT scanner. But, because its specimens are not alive, it can blast fossils, rocks, even pickled lizard heads with higher energy X-rays for longer stretches. Differing densities within the specimen either absorb or transmit the X-rays. This pattern of absorption vs. transmission creates a digital image of the object in 2-D slices ranging from as thick as 5 millimeters to as thin as 5 microns. Medical scanners generally create layers 1 to 2 millimeters thick. Because it maps density differences, the CT scan is a high-resolution look inside any specimen.

“You can see inside the head without having to chop it open,” Rowe says.

To render the digital scan solid, the ThermoJet solid object printer accesses an STL, or stereo lithography file created from the CT scan. It sets down wax layers until it builds the lizard head. Like the scanner, the printer borrows existing technology: rapid prototyping, a key tool in the manufacturing industry for creating solid models from computer-aided design files.

The result is a 3-D replica of the lizard’s head that is three times the size of the original. Or, Rowe could have printed a replica of the lizard’s brain, or a cross section of its sinus cavity.

“There’s no substitute for the real deal,” Rowe says. But the lizard is rare and the real thing hard to find and study, he adds. “Now I know the anatomy of the head of Lanthanotus in far more detail than I know the anatomy of the heads of the gecko lizards living in my backyard.”

The scanner is handy for seeing inside rock samples, too. Lab director Richard Ketcham remembers scanning a diamondiferous eclogite. “It’s one of the only examples of diamonds in their host rock,” Ketcham says. “You can’t study it through thin sections because the diamonds stop the saw.”

The lab has everything from meteorites, salamander heads and tiny fossils in the queue for scanning. According to Ketcham, the department gained funding for the scanner from the work of Rowe, a paleontologist, along with anthropologist John Kappelman and metamorphic petrologist Bill Carlson.

From the lab’s Web site, anyone can access digital files and look inside a purple urchin, or the head of the dinosaur Herrerasaurus ischigualastensis. And those who own a rapid prototyping machine can, for some specimens, download an STL file and create as many replicas of, say, the Texas horned lizard, as they like.

Kristina Bartlett

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