Neutron imaging reveals 66-million-year-old blood vessels in T. rex healing fracture

Inside a broken rib from Scotty, the largest known Tyrannosaurus rex skeleton, lies something paleontologists almost never find: a complete network of blood vessels, still visible after 66 million years. Scientists at Oak Ridge National Laboratory used neutron imaging to peer inside the fossilized bone without damaging it, revealing the intricate vascular system that formed as the dinosaur's body attempted to heal the fracture before death.

The discovery began in 2020 when Jerit Mitchell, then an undergraduate at the University of Regina, used micro-CT scanning—a noninvasive X-ray technique—to examine thin sections of Scotty's rib. The scans showed something unexpected: fossilized soft tissue preserved inside the bone. As the investigation expanded, Mitchell and his colleagues, including physics professor Mauricio Barbi and assistant professor Marcella Berg, layered additional imaging methods on top of the initial findings. They employed synchrotron radiation at the Canadian Light Source and advanced microscopy to study the healing injury and preserved tissues at the cellular level. Each technique revealed different information, but the researchers wanted to know if neutron imaging—a tool rarely applied to paleontology—could expose even more.

In April 2026, the team brought Scotty's rib to Oak Ridge, where they used two specialized neutron instruments: MARS, which generates cold neutrons particularly effective at highlighting hydrogen-rich soft tissues, and VENUS, which produces high-energy neutrons capable of penetrating deep into large objects. Neutrons interact with atoms throughout a specimen in ways that differ fundamentally from X-rays, making them sensitive to features that other imaging methods might miss. The neutron scans confirmed what the X-ray work had suggested and revealed additional details about the fossilized blood vessels and surrounding tissues. The rib told a story of injury and attempted recovery: after the break, iron-rich blood entered the damaged area, and new vessels formed as part of the healing cascade. Scotty died before the fracture fully mended. The dinosaur's remains ended up in a salty marsh, where conditions slowed decomposition and allowed the fragile vascular network to mineralize and survive.

What makes this discovery remarkable is how rarely soft tissues persist in the fossil record. Muscle, blood vessels, and other delicate structures typically decompose long before fossilization can occur. Scotty's rib is an exception—a window into the dinosaur's physiology at a specific moment in time. Barbi called it "winning the lottery." The rib came from Scotty, discovered by teams from the Royal Saskatchewan Museum in the Frenchman River Valley, one of North America's richest dinosaur sites. The rocks in that region preserve a crucial record of dinosaur life in the final moments before the mass extinction that ended the age of nonavian dinosaurs.

The implications extend beyond this single fossil. The research team plans to continue analyzing the data from VENUS and MARS while applying the same imaging approach to other specimens in museum collections. They want to compare patterns of injury and healing across different dinosaur species and examine how ancient pathologies compare with conditions found in modern animals. Mitchell noted that "there are more fossils than you think sitting in collections, hiding secrets from millions of years ago." By combining neutron imaging with X-ray techniques, researchers can investigate biological structures and diseases preserved in bone and amber without ever removing the specimens from their cases. The approach opens a new chapter in paleontology—one where the tools of modern physics allow scientists to read the medical history written into ancient bones.