Fossilized blood vessels found inside healing T. rex rib

Using neutron imaging at Oak Ridge National Laboratory, researchers examined a fractured rib from Scotty, the largest known T. rex skeleton, and discovered a network of mineralized blood vessels preserved from the healing process. The dinosaur died before the fracture fully healed, and a salty marsh environment slowed decomposition, allowing the soft tissue to fossilize. This is a rare find that offers insight into dinosaur biology.

The fracture in Scotty's rib triggered a biological response that created new blood vessels, which then became mineralized over millions of years. Neutron imaging proved essential because it detects light elements like hydrogen, complementing X-ray techniques that reveal heavier elements—similar to how an MRI shows soft tissue while an X-ray shows bone density. The research began in 2020 when Mitchell, then an undergraduate, used micro-CT scanning at the Canadian Light Source to confirm fossilized soft tissue in rib sections. The specimen was discovered in Saskatchewan's Frenchman River Valley, a region rich in Late Cretaceous fossils that documents dinosaur life just before the mass extinction event.