Scans of a T. rex’s broken rib found blood vessels never seen in a fossil before

A broken rib from Scotty, the largest known Tyrannosaurus rex on record, has produced something paleontologists say they have never documented before: a mineralized network of blood vessels frozen mid-repair, 66 million years after the animal was hurt. University of Regina physicist Mauricio Barbi called it “like winning the lottery,” describing a fossil that captured active tissue healing rather than just bone.

The rib came from a skeleton discovered decades ago in Saskatchewan’s Frenchman River Valley, but the vessel network only became visible this year, after researchers sent the bone through two neutron-imaging instruments at a U.S. national laboratory that neither existed nor were accessible to paleontology projects when Scotty was first excavated.

An injury Scotty was still healing from when it died

The rib had broken at some point during the animal’s life, and the fossil record shows the beginning of a repair already underway. Iron-rich blood moved into the fractured area, and new blood vessels started forming as part of the healing process — evidence, researchers say, that Scotty survived the injury for some time afterward rather than dying from it outright. The animal was ultimately preserved in a salty marsh environment, a setting that appears to have slowed the decomposition enough to keep the delicate vessel structures intact.

That timeline matters because soft tissue this fine rarely survives fossilization at all, let alone for tens of millions of years. Bone itself mineralizes readily; blood vessels, built from far more delicate material, normally collapse and disappear long before a skeleton turns to stone.

Neutrons succeeding where earlier scans could not

Researchers had studied Scotty’s rib before, using micro-CT and synchrotron radiation at the Canadian Light Source starting in 2020. Those methods hinted at unusual internal structure but could not resolve it fully. In April 2026, the team sent the bone to Oak Ridge National Laboratory, where two purpose-built instruments took a second pass at the same fossil.

Smaller bones, amber, and scales went through MARS, a cold-neutron imaging station at the lab’s High Flux Isotope Reactor built for high-resolution radiography and computed tomography. Scotty’s rib itself, too large for that setup, went to VENUS, a newer instrument at the Spallation Neutron Source designed to image bigger and more complex samples using a range of neutron energies in a single pass — cutting what once took days of scanning down to a few hours. Neutrons pass through dense material differently than X-rays do, giving the team a way to see structures the earlier synchrotron work had missed.

University of Regina assistant professor Marcella Berg, a former Oak Ridge postdoctoral researcher herself, helped bridge the two institutions for the project. Her prior work at the lab meant the team already understood which of Oak Ridge’s neutron instruments could handle a fossil the size of a T. rex rib, rather than starting that search from scratch once the sample arrived.

A vessel network the lead researcher says has no precedent

Doctoral candidate Jerit Mitchell led the imaging project under Barbi’s supervision, and the two described the result as confirmation rather than a surprise built from nothing — the neutron data lined up with what the synchrotron scans had already suggested, then went further. Mitchell has described fossils generally as capturing only “a tiny snapshot of the past,” a fragment that ordinarily leaves the animal’s biology unreadable in this kind of detail.

What made Scotty’s rib different was scale and clarity: a network extensive enough, and preserved cleanly enough, that Barbi’s team could describe it, in an account of the imaging results, as never before observed in a fossil, in any species. Confirming that claim required comparing the neutron images against known patterns of vertebrate blood vessel healing, checking that the mineralized channels matched a real biological repair process rather than a mineral formation that happened to resemble one.

The largest T. rex on record, found decades before the technology existed to read it

Scotty has ranked as the world’s largest known T. rex since a formal description of the skeleton in 2019, according to the Royal Saskatchewan Museum, which houses the specimen and led its original excavation. The museum’s own figures put Scotty at roughly 8,870 kilograms and 13 meters long, sizable enough to outweigh the Chicago Field Museum’s SUE, another famous T. rex specimen, by about 400 kilograms and more than 50 centimeters in length.

Museum crews found Scotty’s bones in 1991, and full extraction from the rock took more than two decades to complete. That gap between discovery and this month’s finding is itself part of the story: the rib had been sitting in a Saskatchewan collection for years before any instrument capable of imaging its internal blood vessel structure in this much detail was built. Whether other fossils in the same collection hold a comparable healing record is, for now, an open question the neutron instruments at Oak Ridge are only beginning to answer.

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

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