A 66‑Million‑Year‑Old Tyrannosaurus Tooth Embedded in an Edmontosaurus Skull Reveals a Violent Final Encounter

A broken tooth remains lodged in the face of a duck-billed dinosaur that died 66 million years ago. That fragment, preserved in the skull of Edmontosaurus, has now been identified as belonging to Tyrannosaurus, the top predator of its time. In a new study published in PeerJ, researchers report that the fossil preserves rare evidence of a direct encounter between predator and prey.

Bite marks are common in fossils. A predator’s tooth still lodged in the bone is not.

“Finding an embedded tooth is extremely rare,” said study co-author Taia Wyenberg-Henzler in a press release. “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.”

Read More: Jurassic Predators Feasted on Baby Long-Necked Dinosaurs 150 Million Years Ago

Tyrannosaurus Bite in an Edmontosaurus Skull

To determine which predator left the fragment behind, researchers compared the tooth’s shape and size with those of carnivorous dinosaurs known from the Hell Creek Formation. Its serrations and proportions most closely matched those of Tyrannosaurus.

CT scans of the skull provided a clearer view of how deeply the tooth penetrated and how it fractured inside the bone. The scans also helped clarify the angle of impact and its placement within the nasal region.

The tooth is embedded in the front of the snout, suggesting the two animals were positioned face to face at the moment of contact. Additional bite marks on the skull indicate that the encounter involved more than a single strike.

Snapping off a tyrannosaur tooth would have required substantial force. With massive jaws built to withstand high loads, Tyrannosaurus was capable of driving serrated teeth into bone.

“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,” said Wyenberg-Henzler.

Was Tyrannosaurus a Predator or a Scavenger?

The fossil does not determine whether the Edmontosaurus was alive at the time of the bite. The skull shows no evidence of bone healing around the embedded tooth, suggesting the animal did not survive long after the injury, if it survived at all.

“A fossil like this is extra exciting because it captures a behavior: a tyrannosaur biting into this duckbill’s face,” said study co-author John 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,”

The feeding behavior of Tyrannosaurus has been debated for decades. Some evidence points to active predation, while other findings suggest opportunistic scavenging. This specimen does not resolve that question, but it does provide direct evidence of physical interaction between predator and prey.

A Moment Frozen in Bone

Because the skull is nearly complete and retains multiple bite traces, the specimen offers more than a rare piece of behavioral evidence. It allows researchers to examine how tyrannosaurs used their teeth and jaws during feeding.

The Hell Creek Formation represents one of the final dinosaur ecosystems before the mass extinction at the end of the Cretaceous. Tyrannosaurus and Edmontosaurus lived side by side in this environment, making encounters between them likely.

For paleontologists, fossils that record behavior are uncommon. In this case, a single broken tooth contributes to a broader effort to understand how one of the largest terrestrial predators fed, hunted, and competed in the closing chapter of the Age of Dinosaurs.

Read More: Tyrannosaurus Rex Took 40 Years to Grow Up, Fossil Bones Reveal

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• This article references information from a recent study published in PeerJ: Behavioral implications of an embedded tyrannosaurid tooth and associated tooth marks on an articulated skull of Edmontosaurus from the Hell Creek Formation, Montana