July 17, 2013

A fossilized tooth from Tyrannosaurus rex found in the tailbone of a plant-eating dinosaur has provided convincing evidence that the “tyrant lizard king” was, in fact, a fearsome predator–not a scavenger, as some scientists had speculated. Scientists from the University of Kansas discovered the broken tooth and tailbone at a famous fossil site called the Hell Creek Formation in Montana. The scientists concluded that the duckbilled dinosaur had survived its encounter with the T. rex because the area around the tooth had healed. Thus, the plant eater was not a dead animal that the T. rex had scavenged.

A Tyrannosaurus attacks two small plant-eating dinosaurs in an illustration showing the meat eater as a fast, active creature. Tyrannosaurus's skin is tight and scaly, making its body look athletic and limber. (c) Jan Sovak

Tyrannosaurus rex lived during the Cretaceous Period, which lasted from about 145 million to 65 million years ago. The dinosaur has often been portrayed as a deadly predator, but the case for this view was not conclusive. Most scientists believed that T. rex was an active hunter that could run for short distances and may have waited in hiding for its prey to come closer. The dinosaur would then have made a fast dash, attacking the prey with its sharp teeth and strong jaws.

The remains found in the stomach of other T. rex fossils as well as the dinosaur’s fearsome bite and body plan all suggested the beast attacked and ate prey. But some scientists had a different view. They felt that T. rex’s body plan suggested the creature may have been too slow or too clumsy to hunt effectively. Instead, they speculated that the dinosaur may have been a scavenger that feed on dead animals.

Additional World Book articles:

• Prehistoric animal
• Tyrannosaurus rex: The Tyrant Still Reigns (a special report)