A fractured rib from Scotty, the largest known Tyrannosaurus rex skeleton, offers a rare glimpse into the biology of these animals from 66 million years ago. Inside the bone, something almost never found in the fossil record was preserved: evidence of an injury that was still healing when the dinosaur died.
Researchers used neutron imaging at the Oak Ridge National Laboratory, part of the U.S. Department of Energy, to examine the fossil from the inside. The technology allowed for the construction of detailed three-dimensional images without damaging the preserved soft tissues.
“It’s like winning the lottery,” said Mauricio Barbi, a physics professor at the University of Regina in Saskatchewan, Canada. “Scotty's rib contains a vast network of mineralized blood vessels that has never been observed in a fossil before.”
Soft tissues like blood vessels usually disappear during decomposition long before fossilization is complete. Scotty's rib is an unusual exception: it preserves delicate structures that provide insight into what was happening inside the dinosaur's body as the wound healed.
How the vascular network was preserved
After the rib broke, iron-rich blood entered the injured area and new blood vessels formed as part of the healing process. Scotty died before the fracture fully healed. The animal ended up in a salty swamp, where conditions slowed decomposition and helped preserve the fragile network of vessels.
“Every fossil is a little snapshot of the past,” noted Jerit Mitchell, a PhD candidate in physics at the same university, who leads the project under Barbi's direction. Scotty's remains were discovered by teams from the Royal Saskatchewan Museum in the Frenchman River valley, one of North America's richest dinosaur fossil sites.
The rocks in the region preserve an important record of dinosaur life just before the mass extinction that ended the age of non-avian dinosaurs. Researchers are also studying fossilized amber, scales, and bones from other dinosaurs.
“By piecing together the clues, we understand the past and how things might evolve in the future,” said Marcella Berg, an assistant professor of physics at the University of Regina and a former postdoctoral researcher at Oak Ridge.
Neutrons and X-rays as complementary tools
Neutron and X-ray imaging provide scientists with complementary ways to look inside materials. Neutrons are particularly useful for detecting light elements from the periodic table, especially hydrogen, while X-rays are very effective at revealing heavier elements.
The contrast is somewhat similar to the difference between an MRI, which can highlight soft tissues like muscle, and an X-ray, especially useful for viewing dense structures like bone. Researchers choose different techniques depending on the material they want to study.
The work dates back to 2020, when Mitchell, then an undergraduate student, detected evidence of blood vessels within Scotty's rib. At the Canadian Light Source, he first used micro-computed tomography, a non-invasive X-ray imaging method. The scans confirmed fossilized soft tissue in cut sections of the rib.
As the research expanded, they combined other X-ray methods, including synchrotron radiation, with microscopy. Together, these techniques allowed them to study both the healing injury and the preserved fossil tissues at the cellular level.
A new way to search for hidden biology
In April 2026, researchers used the MARS and VENUS instruments at the Oak Ridge laboratory. Neutron imaging allowed them to confirm previous observations, examine large bones like Scotty's rib without damaging them, and obtain additional contrast that complemented the information gathered with other methods.
“Neutrons not only corroborated what we found with synchrotron radiation techniques that led to the discovery of blood vessels, but they also proved to be a very valuable addition to our current studies in search of soft tissue preservation in fossils,” Berg indicated.
Scientists will continue analyzing the data obtained and will extend the approach to other fossils. They also plan to compare injury and healing patterns among different species. By combining neutron imaging with X-ray techniques, they hope to investigate preserved pathologies in fossils and examine how those ancient conditions compare to differences found in modern species.
“There are more fossils than one might think in collections, hiding secrets from millions of years ago,” said Mitchell. “Putting them in a synchrotron or a neutron source allows us to make new discoveries about ancient life like never before.”
