The image of a "ferocious-looking" Tyrannosaurus rex with a "permanent smile" of huge protruding teeth is taking a hit thanks to one Canadian paleontologist, Live Science reports.

Robert Reisz says the T. rex, along with other theropods, actually had scaly lips covering its teeth. “When we see dinosaurs in popular culture, such as in the movie Jurassic Park, we see them depicted with big teeth sticking out of their mouths,” Reisz says in a press release, but he believes that isn't so.

The key is enamel, which theropods' teeth were known to be covered in. Enamel needs to be kept hydrated, the Guardian reports. Otherwise, teeth dry out and become brittle.

"If you have your teeth sticking out, you can’t hydrate the enamel," Reisz says. "You can’t maintain it properly.” But wait, you say, crocodiles—a relative of dinosaurs—have teeth sticking out of their mouth. Reisz says that's because crocodiles live in the water, which provides the necessary hydration. Before you start picturing a T. rex with Mick Jagger's lips, CNN points out that seeing lips on dinosaurs isn't so unusual. For example, the famous velociraptors from Jurassic Park hid their teeth behind lips. But as for T. rex, paleontologist Zhijie Jack Tseng isn't so convinced. In comments to Live Science, he notes that theropods didn't need to worry about tooth quality as much as you might expect because dinosaurs could rapidly replace their teeth. "T.

rex could chip a tooth or get one stuck in prey, and just replace it. Evolving protection for teeth is not a critical component of how they eat." (For T. rex, size originally didn't matter.)

This article originally appeared on Newser: T. Rex May Have Had Lips to Hide Its Ferocious Teeth

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