Why did the dinosaur visit the hospital?
CT scanning has come to underpin most paleontological work. Now, paleontologists say that there is a push to make that rapidly accumulating data more available.
In 1984, paleontologist Glenn Conroy borrowed a fossil from The American Museum of Natural History. It was about 30 million years old – not exactly young, but not old enough to be remarkable, either. It was also a hog fossil, a common one, and it seemed to Dr. Conroy unlikely that anyone would get too emotional about a ruined hog fossil.Skip to next paragraph
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It was the perfect fossil, in short, to be blasted with X-rays in an experiment that might go very wrong.
For most of the time that humans have been looking at fossils – and it’s a long time, dating at least back to Xenophanes’ observation that fossilized shellfish might tell a tale of when Greece was underwater – all that was known about fossils was what was apparent to the eye.
Of course, sometimes, the fossil would break, in an ambiguously happy accident: who knew what stories those exposed insides would tell? Other times, scientists just broke it on purpose.
“If you wanted to know what was inside, the only thing you could do was break it,” said Dr. Conroy, now at Washington University in St. Louis,“and curators of priceless fossils are going to be reluctant to let people do that.”
But one invention meant that curators no longer needed to let anyone ruin anything: the Computerized Tomography, or CT, scanner. Ever since Conroy’s scanned hog, digitally unwrapped from the sediment accumulations of millions of years, appeared on the cover of the journal 'Science,' CT scanners have underpinned almost every paleontological find.
CT scanning has fueled studies of the origins of flight and of dinosaurs’ preposterously long necks. It has furnished enthralling reports of new dinosaurs species. It has turned up a dinosaur heart that, whatever the sins of that dinosaur, looked all too well to scientists like true gold. It has revealed dinosaur embryos swaddled in rock, reserve teeth in dinosaurs’ dental cavities, and tail clubs primed for fending off carnivores.
All of these discoveries have underpinned paleontologists’ better than ever understanding of how these dinosaurs behaved and moved and evolved, and what this millions of years ago world looked like. Dinosaur bones are no longer just bones – with CT, they suggest how the bodies they once supported worked, how these bodies changed, and how these bodies interacted with other bodies in a complex, dynamic ecosystem. Seldom do pre-unwrapped gifts invite much excitement – what’s the fun in that? – but, to paleontologists, the gift has been in the un-wrapping.
“It’s like literally squeezing blood from a stone,” as Conroy put it.
Blood from stone
CT scanners made their debut around 1972, but did so in hospitals, for people. CT scanners use X-rays to take cross-sectional images of an object: the scanner takes a image of one layer, then moves down to take an image of the next layer, and so on. Those images are density-based, so the areas of different density show up in grey-scale shades.
Then, less then a decade after the introduction of those first, now-archaic, scanners, technology advanced enough that individual cross-sections could be digitally reconstructed into a 3D object. At about that time, it also become possible to digitally delete all the scanned material of a certain density, peeling away, say, muscles and tissues and fat to leave behind nothing but a clear, 3D model of a skeleton.
It was about that time that dinosaurs started going to the hospital.
“The first time you talk to a hospital, asking them to scan a 65 million year-old “patient,” they typically look at you as if you are from another planet,” said Robert DePalma, a paleontologist at the Palm Beach Museum of Natural History.
“I simply have to be there as it happens," says Dr. DePalma. "It’s almost like being present for a birth of a new child."
Almost three decades have passed since Conroy’s first 3D fossil model, and in that time many “children” have been born: last month, DePalma found a single T. rex tooth in a CT scan of an herbivore’s healed tailbone, a critical data point that indicated that the T. rex hunted – in this case, albeit not too well – for its meal.
And, all along, the technology has continually improved. Industrial-sized scanners have succeeded medical CT scanners in doing deeply penetrative scans of huge dinosaur bones that don’t fit into a hospital scanner. Micro CT scanners have also emerged to do the fine detail work on small fossils, taking cross-sections that are just micro-millimeters apart. Altogether, on both ends of the scale, the resolution has become sharper, the processing faster.