A T. Rex Bite Left Its Mark on 66-Million-Year-Old Wyoming Bones

A study published July 15, 2026, in the journal PLOS One examined more than 3,000 fossilized dinosaur bones from northeastern Wyoming's Lance Formation, dating to the late Cretaceous period roughly 72 to 66 million years ago. Out of that huge sample, researchers led by Bethania C. T. Siviero of Loma Linda University found just 12 bones bearing tooth traces, and of those, four showed distinct enough patterns to attribute to a specific predator: Tyrannosaurus rex.

The marked bones belonged to Edmontosaurus annectens, a large duck-billed herbivore that was common prey across the same landscape T. rex patrolled. Most of the marked bones showed no evidence of healing, meaning the bites were most likely inflicted at or after the animal's death rather than during a survived attack. The spacing and shape of the four distinct marks matched what's expected from T. rex dentition, though the team notes other contemporaneous carnivores, including smaller theropods and crocodilians, could account for some of the remaining traces.

Part of the value of the study isn't just the marks themselves, but the method: the researchers built out a guide, drawing on prior published research alongside their own findings, for distinguishing genuine tooth traces from bone damage caused by disease, weathering, or other post-mortem processes. That kind of framework matters because bite-mark evidence is one of the few direct windows paleontologists have into how extinct predators actually behaved, feeding or otherwise, rather than just what they looked like.

Fossils that preserve this kind of trace evidence, feeding marks, wear patterns, healed injuries, are exactly what make individual specimens more than decorative. Browse our own fossil specimens, including ammonite and ammolite pieces millions of years in the making.

Source: EurekAlert! / PLOS, July 2026; Phys.org, July 2026.

Written by Nic Scogna, a photographer and mineral collector based in Lexington, Kentucky, and the founder of Crystal Earth Gallery and Kyanite King Minerals. For over 25 years, he has traveled to mineral localities across the U.S. — from Maine to California — personally sourcing the specimens, gemstones, and photographic subjects featured here. When not out in the field, Nic writes about mineralogy, collecting, and the craft of turning raw stone into wearable art.