The T-rex probably hunted alone because there is no fossil evidence (bone beds of T-rex fossils) to support packs of T-rex. A three-horned plant-eater known as the triceratops was food or a prey for the Tyrannosaurus rex. The T-rex used its huge jaws, sharp teeth, and powerful, clawed legs during attacks. The T-rex could not use its two-fingered arms because they were short and useless. Some paleontologists greatly disagree with whether the Tyrannosaurus rex was a carnivore or not. Many believe the Tyrannosaurus rex wasn't as ferocious as we think. He may have just been a scavenger, an animal that simply ate animals that were already dead.