Many dinosaurs are known for their fearsome teeth. Allosaurus had sharp, bladelike choppers. Many were 5 to 10 centimeters (2 to 4 inches) long. Tyrannosaurus rex had bigger ones — the size of bananas. Big teeth are a plus for a predator. But unless a creature can open its mouth very wide, long teeth might actually be a good recipe for starvation. Many big-toothed species survived for millions of years, though. And that is because their jaws could open plenty wide, the better to latch on to big prey, a new study finds.

Explainer: How a fossil forms
Paleontologists can easily measure the size of a fossil tooth. But figuring out how far a dinosaur could open its jaws is trickier. That’s because fossils rarely preserve the soft tissues that once held bones together — and set limits on their movement. Now, a researcher has come up with a way to estimate how widely a dino could open its jaws. This is known as a “gape angle.”