Neutron scans of the largest T. rex ever found show it died with a rib still healing

Scotty, the largest Tyrannosaurus rex skeleton ever discovered, died with a broken rib that had not finished healing, according to neutron imaging carried out at Oak Ridge National Laboratory in April 2026. Inside the bone, researchers found a network of mineralized blood vessels that formed while the injury was mending, a kind of soft-tissue detail that normally decays long before a bone becomes a fossil.

The project is led by Jerit Mitchell, a doctoral candidate in physics at the University of Regina, working under physics professor Mauricio Barbi. Two neutron instruments at the laboratory did the scanning, one at the High Flux Isotope Reactor and one at the Spallation Neutron Source.

A fracture caught in the middle of repair

In a release published September 2, 2026, Oak Ridge National Laboratory, a U.S. Department of Energy lab, laid out the sequence the bone appears to record. After the rib broke, iron-rich blood reached the injured area and new vessels formed to support repair. Scotty then ended up in a salty marsh, where conditions slowed decomposition and helped keep the vessel network intact. Because the animal died before the fracture fully healed, the rib holds an injury still in progress rather than a finished scar. ScienceDaily republished the account on September 23.

Barbi described the find in terms of luck. “It’s like winning the lottery,” he said, adding that “Scotty’s rib contains a vast network of mineralized blood vessels that has never before been observed in a fossil.” That claim of novelty comes from the researchers themselves, and neither the laboratory release nor the ScienceDaily page points to a peer-reviewed paper or a DOI that would let outsiders check it.

The vessels were not first spotted with neutrons. In 2020, Mitchell, then an undergraduate at the University of Regina, detected evidence of blood vessels in the rib using micro-CT scanning at the Canadian Light Source. The team later added synchrotron radiation and microscopy to study the healing injury and its tissues at the cellular level, so the neutron work arrived as a third line of evidence rather than a first discovery. Marcella Berg, a University of Regina assistant professor and former Oak Ridge postdoctoral researcher, said the neutron results corroborated the earlier synchrotron findings.

Two neutron beams, two jobs

Neutrons see differently from X-rays. They are sensitive to light elements such as hydrogen, while X-rays do best on heavier elements, and the laboratory compares the pairing to MRI for soft tissue versus a conventional X-ray for dense structures like bone. Berg said the approach delivers “an incredible amount of detail” about the bone’s properties “without affecting the samples,” which matters when the sample is a 66-million-year-old rib from the largest T. rex skeleton discovered.

The April 2026 beamtime used both of the laboratory’s relevant facilities. MARS, the Multimodal Advanced Radiography Station at the High Flux Isotope Reactor, produces cold neutrons suited to soft-tissue signatures, and the team used it on smaller bones, amber and fossilized scales. VENUS, the Virtual Environment for Neutron Sciences at the Spallation Neutron Source, produces high-energy neutrons that pass through large objects and build detailed three-dimensional images; Scotty’s rib went on that instrument. Hassina Bilheux, the lead instrument scientist for VENUS, listed on her laboratory staff profile, said people often think of neutrons as tools for studying batteries or advanced materials, and the fossil work shows they are just as useful for ancient life.

Scotty was not the only specimen. The release says a hadrosaur rib from the Royal Tyrrell Museum collection was also scanned on VENUS, and preserved Edmontosaurus scales went through MARS. Mitchell framed the larger aim in terms of museum collections, saying many more fossils sit in them than people think, “hiding secrets from millions of years ago.” A video produced by the laboratory shows the imaging and an animation of the process.

What is known about Scotty itself

The skeleton’s size claim predates the scans. In 2019, University of Alberta paleontologists led by Scott Persons published a study in The Anatomical Record titled “An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex.” According to the university’s summary of that work, leg bones suggest a living weight of more than 8,800 kilograms and a length of about 13 metres. The animal was probably in its early 30s when it died, unusually old for the species, and was found in 1991 in Saskatchewan, encased in sandstone. “This is the rex of rexes,” Persons said, while also predicting that “there will always be bigger discoveries to be made.”

The remains were recovered by Royal Saskatchewan Museum research teams in the Frenchman River Valley, which the ScienceDaily account describes as one of the richest dinosaur fossil sites in North America. The museum holds the skeleton. Wording matters here: the 2026 sources call Scotty the largest T. rex skeleton discovered, and the 2019 study frames it as the largest known specimen, so the superlative describes what has been found so far and is open to revision if something bigger comes out of the ground.

Analysis of the VENUS and MARS data is continuing. The team plans to apply the same approach to more fossils, compare injury and healing patterns across species, and compare ancient pathologies with those seen in modern animals. Mitchell argues that putting fossils in a synchrotron or neutron source makes new discoveries about ancient life possible “like never before,” and the next test of that claim will be whether the vessel network in Scotty’s rib shows up in other animals.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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