Lately, scientists have suggested that Tyrannosaurus rex wasn't the vicious hunter from the movies—instead, with its slower speeds and weak eyesight, it was a scavenger, they argue. But a new finding offers clear evidence against that rather disappointing theory. Researchers have discovered a T. rex tooth lodged in the spine of another dinosaur—whose tailbone had healed, indicating the T. rex attacked a live, not dead, creature, the Wall Street Journal reports. "It's not just a smoking gun—we've actually found the bullet," says the paleontologist who co-authored the study, per National Geographic.
The Florida-based paleontologist who made the discovery in the spine found in Montana says "as soon as I could see that tooth lodged in the side, I knew it was an extremely significant piece," he says. That was confirmed via a microscopic inspection of the 1.5-inch-long tooth's serrations. "We were able to conclusively identify the tooth as coming from a Tyrannosaurus rex and no other dinosaur." The four-ton victim was a hadrosaur, a plant-eater that lived in what's now the American West. But some scientists say the tooth isn't quite proof: "It's one data point, and that's the least amount of data you can have," notes one. (Read more Tyrannosaurus rex stories.)