Rare fossil at Montana State’s Museum of the Rockies records Tyrannosaurus attack

A fossil on display at Montana State University's Museum of the Rockies reveals how dinosaurs in the Tyrannosaurus genus may have subdued prey, and the specimen is the focus of a new collaborative research publication between scientists at MSU and the University of Alberta in Canada.

The giant carnivorous dinosaur Tyrannosaurus roamed the region that is now Montana at the end of the Age of Dinosaurs, about 66 million years ago. It lived alongside other large dinosaurs, including plant-eaters like Triceratops and the duck-billed Edmontosaurus.

In 2005, a nearly complete Edmontosaurus skull was found in the Hell Creek Formation of eastern Montana on lands managed by the Bureau of Land Management. The skull is now housed in the paleontology collection at Museum of the Rockies, and it contains a telling detail: lodged inside its face is the tooth of a tyrannosaur.

Now on display in the museum's Hall of Horns and Teeth, the skull became the focus of a collaboration between University of Alberta doctoral student Taia Wyenberg-Henzler and Museum of the Rockies' Curator of Paleontology John Scannella. The results of their research were published today 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."

Comparing the embedded tooth to all the carnivorous inhabitants in the Hell Creek Formation revealed that it most closely matched with the teeth of Tyrannosaurus. CT scans of the skull, performed at Advanced Medical Imaging at Bozeman Health Deaconess Hospital, helped provide greater detail.

"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."

"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."

The feeding habits of Tyrannosaurus, one of the largest meat-eating animals to ever walk the Earth, have been the subject of study and debate for decades. The tooth inside this Edmontosaurus skull provides a further glimpse into Tyrannosaurus behavior, Scannella said.