Around 66 million years ago, near the end of the Age of Dinosaurs, Tyrannosaurus ruled what is now Montana. The massive predator shared its environment with other giants, including the horned Triceratops and the duck billed herbivore Edmontosaurus.

Embedded Tyrannosaurus Tooth Tells an Ancient Story

In 2005, researchers uncovered a nearly complete Edmontosaurus skull in the Hell Creek Formation of eastern Montana on land managed by the Bureau of Land Management. The fossil is now part of the Museum of the Rockies' paleontology collection, where one extraordinary feature immediately stands out: a broken tyrannosaur tooth remains lodged in the animal's face.

The skull is currently displayed in the museum's Hall of Horns and Teeth and became the centerpiece of a collaborative investigation led by University of Alberta doctoral student Taia Wyenberg-Henzler and Museum of the Rockies Curator of Paleontology John Scannella. Their findings were published in the scientific journal PeerJ.

"Although bite marks on bones are relatively common, finding an embedded tooth is extremely rare," said Wyenberg-Henzler. "The great thing about an embedded tooth, particularly in a skull, is it gives you the identity of not only who was bitten but also who did the biting. This allowed us to paint a picture of what happened to this Edmontosaurus, kind of like Cretaceous crime scene investigators."

CT Scans Help Reconstruct the Attack

To identify the predator, the researchers compared the embedded tooth with those of every known meat eating dinosaur from the Hell Creek Formation. The match pointed to Tyrannosaurus. CT scans performed at Advanced Medical Imaging at Bozeman Health Deaconess Hospital provided additional detail about how the tooth became trapped in the skull.

"A fossil like this is extra exciting because it captures a behavior: a tyrannosaur biting into this duckbill's face," said Scannella. "The skull shows no signs of healing around the tyrannosaur tooth, so it may have already been dead when it was bitten, or it may be dead because it was bitten."

Rare Fossil Offers New Clues About Tyrannosaurus Behavior

According to Wyenberg-Henzler, the position of the tooth provides important clues about the encounter between predator and prey.

"Looking at the way the tooth is embedded in the nose of the Edmontosaurus suggests that it met its attacker face-to-face, something that usually happens to an animal that was killed by a predator," said Wyenberg-Henzler. "The amount of force necessary for a tooth to have become broken off in bone also points to the use of deadly force. For me, this paints a terrifying picture of the last moments of this Edmontosaurus."

Scientists have debated the feeding habits and hunting behavior of Tyrannosaurus for decades. As one of the largest meat eating animals ever to walk the Earth, it has long been the focus of paleontological research. This rare fossil, with its embedded tooth preserved for millions of years, provides another valuable piece of evidence about how the iconic predator may have hunted and subdued its prey.