A fractured rib from Scotty, the largest Tyrannosaurus rex skeleton ever discovered, is giving researchers a rare look at dinosaur biology from 66 million years ago. Preserved inside the bone is something almost never found in the fossil record: evidence of an injury that was still healing when the animal died.
Scientists used neutron imaging at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) to examine the fossil from the inside. The technology allowed them to construct detailed 3D images without damaging the preserved soft tissue.
“It’s like winning the lottery,” said Mauricio Barbi, professor of physics at the University of Regina (U of R) in Saskatchewan, Canada. “Scotty’s rib contains a vast network of mineralized blood vessels that has never before been observed in a fossil.”
Fossilized Blood Vessels Preserve a Rare Moment
Soft tissues such as blood vessels usually disappear during decomposition long before fossilization is complete. Scotty’s rib is an unusual exception, preserving delicate structures that provide a glimpse of what was happening inside the dinosaur’s body while the injury was healing.
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 had completely healed. The dinosaur ended up in a salty marsh, where conditions slowed decomposition and helped preserve the fragile network of blood vessels.
“Every fossil is a tiny snapshot of the past,” said Jerit Mitchell, a U of R doctoral candidate in physics who leads the project under Barbi’s direction.
Scotty’s remains were discovered by teams from the Royal Saskatchewan Museum in Saskatchewan’s Frenchman River Valley, one of North America’s richest sites for dinosaur fossils. Rocks in the region preserve an important record of dinosaur life shortly before the mass extinction that ended the age of nonavian dinosaurs. Researchers are also studying fossilized amber, dinosaur scales and bones from other dinosaurs.
“By piecing the clues together, we understand the past and how things could evolve in the future,” said Marcella Berg, a U of R assistant professor of physics and former ORNL postdoctoral researcher.
Neutrons and X-rays Reveal a Dinosaur Medical Record
Neutron and X-ray imaging provide researchers with complementary ways to see inside materials. Neutrons are particularly useful for detecting light elements on the periodic table, especially hydrogen, while X rays are highly effective at revealing heavier elements. The contrast is somewhat similar to the difference between an MRI, which can emphasize soft tissues such as muscle, and an X ray, which is especially useful for viewing dense structures such as bone. Researchers select different neutron and X-ray techniques depending on the material they want to investigate.
The work traces back to 2020, when Mitchell, who was then a U of R undergraduate, detected evidence of blood vessels inside Scotty’s rib. At the Canadian Light Source, he first used micro-CT scanning, a noninvasive X-ray imaging method. The scans confirmed fossilized soft tissue in cut sections of the rib.
As the investigation expanded, researchers combined other X-ray methods, including synchrotron radiation at the Canadian Light Source, with microscopy. Together, those techniques allowed the scientists to study both the healing injury and preserved fossil tissues at the cellular level.
Once X-ray imaging had exposed evidence of the fossilized blood vessels, the researchers turned to neutrons in hopes of finding additional clues from the vessels and other soft tissues.
Powerful Neutron Beams Peer Inside Scotty’s Rib
In April 2026, the researchers used the Multimodal Advanced Radiography Station (MARS) instrument at ORNL’s High Flux Isotope Reactor (HFIR) and the Virtual Environment for Neutron Sciences (VENUS) instrument at DOE’s Spallation Neutron Source (SNS) at ORNL.
Neutron imaging allowed the team to confirm earlier observations, examine large bones including Scotty’s rib without damaging them, and obtain additional image contrast that complemented the information gathered through other methods.
“Neutrons not only corroborated what we found with synchrotron radiation techniques that led to the discovery of blood vessels in Scotty’s rib, but they also proved to be a highly valuable addition to our current studies in search of soft tissue preservation in fossils,” said Berg. “This gives us an incredible amount of detail to better understand these properties without affecting the samples.”
MARS generates cold neutrons that are particularly effective at highlighting signatures associated with soft tissue, areas rich in hydrogen and subtle differences within a specimen. Researchers used the instrument to produce high-resolution images of smaller bones, amber and fossilized scales.
VENUS, by contrast, produces high-energy neutrons capable of penetrating deeper into large objects and generating detailed 3D images. The researchers used VENUS to examine larger bones, including Scotty’s rib.
A New Way to Search Fossils for Hidden Biology
As neutrons pass through a specimen, they interact with atoms throughout the material and are especially sensitive to hydrogen atoms. Those interactions generate information that can be converted into images. Because neutrons behave differently from X rays, they can expose features that may be difficult or impossible to detect with other imaging technologies.
“People often think of neutrons as tools for studying batteries or advanced materials, but they’re just as innovative for answering questions about ancient life,” said Hassina Bilheux, lead instrument scientist for VENUS.
Researchers will continue studying the data collected at VENUS and MARS while extending the approach to additional fossils. They also plan to compare patterns of injury and healing among different species.
By combining neutron imaging with X-ray techniques, the scientists hope to investigate pathologies preserved in fossils and examine how those ancient conditions compare with differences found in modern species.
“There are more fossils than you think sitting in collections, hiding secrets from millions of years ago,” Mitchell said. “Putting them in a synchrotron or neutron source allows us to make new discoveries about ancient life like never before.”
