Kiss Me Deadly: Did T-Rex Have Lips All Along?

Far from the toothy, snarling monster we've come to know and love, Tyrannosaurus rex—and other theropods like it—might have sported a pair of lips, argues Robert Reisz, a paleontologist at the University of Toronto's Mississauga campus, who's presenting his theory on Friday at the annual Canadian Society of Vertebrate Paleontology meeting.

"This has bothered me for a long time," Reisz told Motherboard, "the way scientists represented dinosaurs, especially theropods, with their teeth sticking out." Not to mention "popular movies," he said (looking at you Jurassic Park), and museum exhibits.

A gruesomely fanged T. rex makes a great movie monster, but in real life, to Reisz at least, it doesn't make a whole lot of sense. The only comparable animals alive today with teeth that stick out are crocodiles, which are aquatic, he noted, unlike virtually all theropods, Spinosaurus being an exception.

The sticking point for Reisz is the fragile enamel that covers dinosaurs' teeth. According to him, reptiles tend to have thin enamel on their teeth to begin with. "Even something as big as a T. rex had thin enamel," he said, about one-quarter-of-a-millimeter thick. "If exposed, it would deteriorate and wear down quickly," meaning T. rex's teeth would rot. Reptiles have "glandular secretions in the mouth," he said, "which remineralize the enamel and maintain its integrity. That can't happen if teeth are exposed permanently."

As for animals like elephants and warthogs, well, they do have exposed tusks—but these aren't coated with the same kind of fragile enamel as a dinosaur's teeth.

It's not that T. rex would have had a big, juicy kisser. More likely it had thin, scaly lips like a Komodo dragon, Reisz believes. "Proportionally, their teeth are as large as theropods."

When he spoke to Motherboard, Reisz hadn't yet had a chance to present his as-yet-unpublished research to other paleontologists, so he couldn't speak to whether it would be controversial. But many scientists are starting to think more about dinosaurs' "soft tissues," including where their nostrils might have gone, he said, questions that were long ignored—or hard to tackle, anyway, based on the dino bones these creatures left behind.

Still, there's something to be said for taking it slow. The field of paleontology is changing so quickly that the old and cherished ideas of T. rex as a big, scaly monster are quickly going out the window. Now scientists think that theropods like T. rex probably even had feathers. If Reisz is right, they might have had a grimacing pair of lips, too.