Why did the Tyrannosaurus rex—one of the largest and most fearsome dinosaurs that ever lived— have such small arms? This question has puzzled paleontologists for over a century. But a detailed scan of a T. rex fossil could finally help solve this mystery.
Researchers analyzed the forearm of a T. rex nicknamed Sue, housed at the Field Museum in Chicago, Illinois. The 3-D image revealed the internal structure of Sue’s arm bones. “This will tell us whether T. rex even used its arms,” says Bill Simpson, a paleontologist at the museum. Early results reveal that Sue’s bones don’t show many signs of stress, suggesting the dino may not have used her tiny appendages very much.