Argonne’s x-ray beam shines on Sue and shows she didn’t use those little arms

Sue, the Field's famous T. rex, lost an arm for a few days as the limb underwent a high-powered x-ray examination at Argonne National Laboratory near suburban Lemont. (Hannah Moulthrop/MEDILL)

By Hannah Moulthrop

T. rex decimated prey with those mighty jaws and powerful legs and tail. But one of the great mysteries of the mighty dinosaur is how it used those tiny arms.

Preliminary study of T. rex Sue’s right arm shows a lack of use and possible evidence of gout in her fingers.

Scientists at the Field Museum in Chicago removed the arm and sent it for high-powered imaging by the Advanced Photon Source at Argonne National Laboratory near Lemont. Sue got her arm back and some answers today.

Sue weighed between seven to ten tons, while having arms as small as an adult human’s, said Peter Makovicky, the Field’s associate curator of dinosaurs.

Argonne’s scanner shot the brightest x-ray beams in the Western Hemisphere to “see” into the bones and find any evidence of wear and tear such as micro-fractures. The detector beam, a powerful CT scanner, revealed that Sue may not have used her arm much at all.

Bones that are well used have a firm structure due to calcium storage, said Carmen Soriano Hoyuelos, a beamline scientist with the Advanced Photon Source at Argonne. But Sue’s arm bones were very hollow, indicating a lack of use that would have made them more brittle, she said.

Two of Sue’s fingers subjected to the high-resolution scan show their microstructure and reveal another aspect of the dinosaur’s life.

“Sue has a lot of points of disease and injury in her skeleton” overall, Makovicky said, mentioning “evidence of broken ribs, evidence of infection, arthritis” and even tail injuries.

“So one of the fingers shows what people have seen, thinking or interpreting it as gout. If you have a very acute case of gout, what you see is the bones eaten up,” said Soriano Hoyuelos, adding that dinosaurs are not the same as humans and that the lab is still looking for evidence of disease.

Gout in humans is an acute form of arthritis that results from too much uric acid in the body. High uric acid levels can be associated with excessive alcohol consumption or use of medication such as diuretics.

While Sue’s arm was reattached Wednesday morning and is back on display, Soriano Hoyuelos and Makovicky among others still have lots of scanner data to process.

Soriano Hoyuelos estimated that studying all of the data could take one to two months.

“Sue is still the most complete T. rex yet found, so there’s a wealth of information there,” Makovicky said. The next step will be to compare the results to data from other predatory dinosaurs, he said.

The Advanced Photo Source at Argonne is used for analysis of everything from pharmaceutical components to mechanical processes such as fuel injection. This is the first time it has been used to evaluate a dinosaur fossil.

Photo at top: Sue, the Field’s famous T. rex, lost an arm to a high-powered x-ray examination at Argonne National Laboratory near suburban Lemont. The arm and some results are back. (Hannah Moulthrop/MEDILL)