A broken rib from Scotty, the largest Tyrannosaurus rex skeleton discovered, is helping scientists uncover new information about life on Earth 66 million years ago. Scotty's rib preserves something rarely seen in the fossil record: a healing injury frozen in time.
Using neutron imaging at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL), the scientists peered inside the fossilized bone to build 3D views without altering 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."
University of Regina scientists used neutrons at ORNL to map preserved soft tissue in an unhealed T. rex rib. Iron-rich blood and the salty marsh where the animal died helped preserve the delicate structures, and neutrons' sensitivity to light elements made these long-hidden details visible. This animation contains an image published under CC BY 4.0 International Deed and altered in accordance with the license. Credit: Phoenix Pleasant/ORNL, U.S. Dept. of Energy
Fossilization rarely preserves soft tissues, such as blood vessels, which are typically lost through decay over time. Scotty's rib proves to be an extraordinary exception.
When the break occurred, iron-rich blood flowed into the area, forming blood vessels to promote healing. But before his broken rib fully healed, Scotty died in a salty marsh, which slowed decomposition and contributed to the preservation of the delicate 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.
Research teams from the Royal Saskatchewan Museum discovered Scotty's remains in Saskatchewan's Frenchman River Valley, one of North America's richest dinosaur fossil sites. The region preserves an invaluable window into the world of dinosaurs just before their extinction. The team is also examining 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.
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Neutron and X-ray techniques form a powerful discovery pipeline for materials science. Neutrons reveal light elements on the periodic table - especially hydrogen - with exceptional clarity, while X‑rays excel at showing heavier elements. The difference in results is like the difference between an MRI, which highlights soft tissues such as muscle, and an X‑ray, which highlights dense structures such as bone. Scientists choose different neutron and X-ray techniques depending on the properties of the materials they are studying.
The team's work builds on research that began in 2020 when Mitchell, then a U of R undergraduate, discovered evidence of blood vessels in Scotty's rib. Working at the Canadian Light Source, Mitchell initially applied a noninvasive form of X-ray imaging known as micro-CT scanning. This technique confirmed the presence of fossilized soft tissue from cut slices of Scotty's rib. As the project progressed, the team combined additional X-ray techniques, such as synchrotron radiation also at the Canadian Light Source, with microscopy to examine the healing process and fossilized tissues at the cellular level.
After revealing the fossilized blood vessels with X-ray techniques, the researchers sought neutrons to spot more clues left behind by the blood vessels and other soft tissue.
In April 2026, the team turned to 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. They used neutrons to verify their prior findings, to nondestructively measure large bones, including Scotty's rib, and to gain image contrast, complementing results from the other techniques.
"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 produces cold neutrons, which are excellent for revealing soft tissue signatures, hydrogen-rich areas, and fine contrast. The team used MARS to create high-resolution images of smaller bones, amber and fossilized scales. VENUS produces high-energy neutrons, which are excellent for revealing deep internal features and producing 3D images of large samples. The team used VENUS to create high-resolution 3D images of the larger bones, including Scotty's rib.
During imaging experiments, neutrons interact with all atoms - with particular sensitivity to hydrogen atoms - providing the data needed to create the images. Thanks to their unique properties, neutrons can uncover information that is difficult or impossible to obtain through other techniques.
"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.
The team plans to continue analyzing data collected at VENUS and MARS, expand studies to additional fossils, and compare healing patterns across species. Combining neutron imaging with X-ray techniques, they will also investigate pathologies in fossils and compare differences 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."
HFIR and SNS are both DOE Office of Science user facilities.
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science . - Sumner Brown Gibbs
