The dinosaur was injured. A crack in one of its ribs was beginning to heal when the largest Tyrannosaurus rex ever to walk the Earth died sixty-six million years ago.
Today, a physics student named Jerit L. Mitchell at the University of Regina was examining a scan of that same rib. He noticed strange shapes inside the bone that seemed unusual. The dinosaur, called Scotty, is the largest and most complete T. rex specimen ever discovered. It now rests in the Royal Saskatchewan Museum.
What Mitchell and his team found, published in Scientific Reports in 2025, was something paleontologists had long hoped to see but rarely managed: preserved blood vessels frozen inside the bone of a Tyrannosaurus rex. These vessels were not soft or red. Instead, they survived as iron-rich mineralized casts, where minerals replaced the original tissue as the body fossilized.
Regular hospital CT scanners could not see through the dense fossil bone. So in 2019, the team brought the rib to the Canadian Light Source, the country's only synchrotron, which produces X-rays powerful enough to see through stone. Without breaking the bone, they created a detailed three-dimensional model of the rib's interior.
The blood vessels were concentrated in the regions where the rib was actively healing. This suggests that damaged bones with healed injuries may preserve soft tissue better than uninjured bones. For decades, paleontologists searched pristine specimens, but Scotty's rib indicates they may have been looking in the wrong place. The damaged bones, the ones that hurt, may hold the answers to how dinosaurs healed.