A remarkable fossil discovery has given scientists one of the clearest pieces of evidence ever found of a predator-prey encounter between dinosaurs. While examining a nearly complete Edmontosaurus skull discovered in Montana’s Hell Creek Formation, researchers identified a broken tooth still embedded in the dinosaur’s nasal bone. Dating back approximately 66 million years, the fossil preserves what appears to be a violent encounter frozen in time. The skull is now housed at the Museum of the Rockies.

The discovery was made by researchers including Taia Wyenberg-Henzler of the University of Alberta and John Scannella of Montana State University. Using CT scanning and detailed anatomical analysis, the team matched the tooth’s distinctive size, shape, and serrated edges to Tyrannosaurus rex, the apex predator that dominated North America at the end of the Cretaceous Period.

Although dinosaur bones bearing bite marks have been discovered many times before, an attacker leaving a tooth behind is extraordinarily rare. Embedded teeth provide direct evidence linking both the predator and its victim in the same fossil, allowing paleontologists to identify not only what happened but also which species were involved. In this case, the position of the tooth suggests the Tyrannosaurus bit the Edmontosaurus head-on, and the force of the attack was powerful enough to snap the tooth off inside the victim’s skull.

Whether the attack occurred during an attempted hunt or while the Tyrannosaurus was scavenging after the animal’s death remains uncertain. However, the fossil captures a real interaction between two dinosaurs that lived at the very end of the Age of Dinosaurs, just before the mass extinction event that wiped out non-avian dinosaurs around 66 million years ago.