The Tyrannosaurus Rex is the famous monster predator dinosaur. It walked on its hind legs, had stumpy little front legs whose purpose (if any) is somewhat mysterious, and had a huge mouth full of teeth. In the popular imagination, it was a top-level predator that went around chasing and eating any of the other big herbivore dinosaurs it could catch.
Some scientists, however, turned against this view. They took to arguing that the Tyrannosaurs Rex could not have been this kind of predator. Instead, they saw it more as a giant scavenger, a carrion feeder who would lumber around until it had found an animal that had died of natural causes or been taken down by smaller and nimbler predators. The Tyrannosaurus would then tuck in. These kill-joy scientists are no doubt associates of the others who argue that the giant winged dinosaurs were only able to glide and could not truly fly.
However, a recent discovery seems to have established that the Tyrannosaurus Rex was a top-level predator after all and no pathetic scavenger. Palaeontologists working in South Dakota found the fossilised skeleton of a Hadrosaur, a large Cretaceous herbivore, with the tooth of a Tyrannosaurus Rex embedded in its spine. It appeared that the Tyrannosaurus had attacked the Hadrosaur and bitten into its back, whereupon the tooth had come loose, but the herbivore escaped and survived the encounter.
This finding seems to prove that the Tyrannosaurus Rex was a hunting animal. Like any hunter, it would eat carrion if it found it, but it would also attack other animals, albeit not always with success.
T rex tooth found embedded in prey, restoring dinosaur's reputation
A near miss for a Tyrannosaurus rex: evidence of failed predation
"Her Pack of Tyrannosaurs Came Screeching to Her Side!" (image source)