Wired Science

Digital Scanner Brings Fossils Into 3-D View - and Exposes Fake Ones

When researchers at an advanced computer scanning project at the University of Texas at Austin helped discover a previously unknown type of winged dinosaur recently, it made headlines around the world (see Virtual Paleontology for the whole story). But that's only one of the milestones the university's High-Resolution X-ray Computed Tomography Facility - UTCT for short - has racked up in the past few years.

UTCT is home to one of the world's only high-powered 3-D X-ray machines designed specifically for paleontological research. In essence, it lets scientists peer inside an object - a skull, a fossil, a sea urchin - without damaging it. The machine is basically a hospital-type CAT  scanner on steroids. It blasts X-ray beams - far more powerful than a human body could withstand - through solid objects. The beams capture an image of a narrow slice of the target. Hundreds of those slices are then stacked on top of each other to form a three-dimensional image of the object, which can be viewed from any angle - including from the inside . The university then makes those images available to all comers on the Web at www.digimorph.org.

Since Digimorph's launch in 2002, more than 100 researchers from some of the world's top natural history museums and universities have sent in specimens to be scanned - including the world's oldest dinosaur, smallest bat, and oldest bird, not to mention dozens of more prosaic specimens like gorillas, lizards, turtles, and wolverines. For students and scientists, those hundreds of images offer an unprecedented opportunity. Not long ago, to get a close look at the skull of that oldest dinosaur - the Herrerasaurus, if you want to be formal - would have required a trip to a museum in Argentina, which houses the only such bit of bone ever discovered. Now, anyone with an Internet connection can not only see that skull in high-definition detail, they can turn it around and upside down and even "move" through it from the inside, slice by slice.

The technology has also solved some serious scientific puzzles. For decades, researchers at the National Geographic Society wondered what to do with one of their most treasured finds: the world's largest egg. It was one of the few intact remnants of the extinct elephant bird, a huge ostrich-like creature that once inhabited Madagascar. How to find out if the egg contained an embryo without destroying it? They finally got an answer when they took it to UTCT. A scan did indeed find an embryo complete with beak, feet and vertebrae inside, giving scientists a trove of new information on how the elephant bird developed.

On another occasion the scanner exposed a paleontological fraud. A fossil found in China was widely touted - on the cover of National Geographic and elsewhere - as that of a creature proving a link between birds and dinosaurs. Under the exacting eye of the CT scan, however, it turned out to be a collage of rock and fossil fragments glued to a piece of shale.

Impressive as its results are, the CT scanner's slice-and-reassemble technique isn't an entirely original concept in paleontology. Professor Erik Jarvik of the Swedish Museum of Natural History applied the same technique to a lobe-finned fish fossil - albeit in considerably less high-tech style. Jarvik ground the fossil down in layers that measured a fraction of a millimeter each, drawing and photographing each layer before continuing on to the next. He then cut thin sheets of wax to match the outlines of the bones in each drawing, and stacked them on top of each other to build a complete model. In other words, he did just what the CT scan does, but he did it by hand. The only other difference? He destroyed the fossil in the process - and it took over ten years.