The Field Museum in Chicago will send an arm from its famed Tyrannosaurus rex to the Argonne National Laboratory in southwest suburban Lemont for testing.

Scientists are hoping to find out if the dinosaur’s tiny forelimbs were useful.

The bones were removed Thursday morning, making the skeleton, nicknamed Sue, “a one armed bandit,” according to McCarter Collections Manager of Fossil Vertebrates Bill Simpson.

Once the bones arrive in Lemont, Argonne will scan them in a process similar to a CT scan that is about a million times more powerful.

Scientists will be looking for signs of stress and strain in the bones, which would indicate how much — or little — they were used during Sue’s life. 

Pete Makovicky, the associate curator of dinosaurs at the The Field Museum, said frequent use leaves “a very characteristic trace” that can easily be seen under a microscope.

“We don’t want to cut Sue’s bones open and put them under a microscope, so this is a different way of doing that,” Makovicky said.

He noted this is the biggest project The Field Museum and Argonne have done together.

The tests will help answer the question of why T. rex had such short arms, and what were they used for.

“The arms of T. rex are one of those conundrums in evolution that keep coming up and haven’t really been answered,” Makovicky said. “We’re gonna ask a very fundamental question here, which is, were the arms used much at all?”

Makovicky said scientists have come up with many theories over the years, including that the tiny arms were somehow key to reproduction, although no one could really explain how that would work.

“Another good one was, in the 70s, there was a theory that T. rex needed just a little bit of lift as it was getting off the ground,” Makovicky said. “There was actually a scientific paper that … had a cartoon of a T. rex going from a seated position up, and the end of it was hilarious, it had to sort of throw its head back to get the weight going and then do a little push up with its tiny arms.”