A 65-million-year-old fossil from an herbivore dinosaur could be evidence that the Tyrannosaurus rex was, in fact, a hunter, the Wall Street Journal reported.

Until the study was published Monday, paleontologists widely believed the t-rex to be a scavenger. The researchers analyzed a tooth found in the spine of a hadrosaurus, but the bone had healed over the steak-knife-like tooth.

This indicated to the researchers that the dinosaur had survived the t-rex's attack and was able to escape and likely lived for years.

"The animal was attacked, survived and escaped," said paleontologist David Burnham at the University of Kansas Biodiversity Institute, who helped to analyze the fossil. "Until we found this specimen, people could say that t-rex was a scavenger; here is evidence it attacked living things."

According to scientists, the t-rex had a bite stronger than any known predator and could bite off 500 pounds of flesh in one mouthful.

"This is smoking-gun evidence that, in fact, Tyrannosaurus did attack animals and did not just go after carrion," said paleontologist Mark Norell at the American Museum of Natural History in New York, who was not involved in the find.

Robert DePalma II, a Paleontologist at the Palm Beach Museum of Natural History in Florida, discovered the fossil on a 2007 field expedition.

"It was a very odd bone at first glance," he said. "As soon as I could see that tooth lodged in the side, I knew it was an extremely significant piece."

Norell said the find was extremely rare, because it is hard to find fossils that old so well preserved.

"Here, we are lucky enough to have found a fossil that is a snapshot of things that happened millions of years ago," he said.

Some paleontologists believed the t-rex only preyed on dead animals and various finds have been hard to identify until the most recent discovery.

"We see puncture marks and gouges from teeth, but the teeth themselves aren't there," said dinosaur expert Thomas Holtz at the University of Maryland. "There was a lack of positive evidence that Tyrannosaurus rex had done it."