A paleontologist at Yale University has uncovered evidence that the fearsome carnivore, one of the largest ever to walk the Earth, may have been a cannibal who sometimes dined on fellow T. rexes.
Nick Longrich first got the idea after noticing what appeared to be T. rex bite marks on the ancient toe bone of one of the killer beasts.
After that discovery, he scoured fossil records in the United States and Canada, eventually coming up with three more instances of a T. rex apparently making a meal out of its own.
"Until now we had only one documented example of cannibalism in dinosaurs, so you'd tend to assume it's pretty rare," Longrich told LiveScience. "All of a sudden, we have four examples of cannibalism in T. rex. So that's definitely a surprise."
It's not unusual for carnivores to chow down on their own species. A crocodile will happily eat another croc, while even pigs, which are omnivores, will eat a pig carcass if they can.
What's not clear is whether the T. rex was an opportunistic scavenger of T. rex carcasses, or whether the dinosaurs would actually fight one another.
"I wouldn't rule out the possibility of some sort of intraspecies combat going on," Longrich told National Geographic.
"We see that today when animals like bears and lions take each other out. They are competing with one another, and the best way to get rid of your competitor is to get rid of him for good."
The T. rex roamed the planet more than 65 millions years ago during the Cretaceous period. Fossil records suggest it was about 40 feet long and stood as high as 20 feet.
Its serrated, conical teeth may have allowed it to bite off as much as 500 pounds of meat in a single mouthful. There's also evidence to suggest the creature's jaws were powerful enough to shatter bones.
"T. rex was just so powerful, with those teeth like railroad spikes, that it left deep puncture marks," Gregory Erickson, co-author of the T. rex study, told National Geographic.
The research was published in the PLoS ONE journal on Friday.