New Study Challenges Long-Held Belief About T. rex and Other Large Theropod Dinosaurs’ Teeth

A new study published in the journal Science challenges the long-held belief that large theropod dinosaurs, including the iconic Tyrannosaurus rex, had exposed teeth when their mouths were closed. The study indicates that their teeth were concealed by slim, scaly lips akin to those of contemporary Komodo dragons.[0] The discoveries may have an effect on our comprehension of dinosaur dental structure, eating habits, mechanical properties, and how they are depicted in both academic and mainstream media.[0]

Contradicting more than a century's worth of scientific and popular images, the study reveals that the large teeth of Tyrannosaurus rex and other toothy theropod dinosaurs were likely completely covered by thin, scaly “lips” when the mouth was closed. In addition, the researchers discovered minuscule openings in the theropods' mandibles that were positioned in a comparable manner to those in modern-day lizards, which provide nerves and blood vessels to the gums and lips. Furthermore, both theropods and lizards possess vertical teeth, in contrast to crocodiles that have outward-leaning teeth.[1] Additionally, when modeling the closure of the mouths of theropods without lips, it was observed that in order to fully close the mouth, the lower jaw had to either crush the bones that support the jaw or dislocate the jaw joint.[2]

According to the investigation, lipless animals displayed a distinct tooth wear pattern from carnivorous dinosaurs. Additionally, dinosaur teeth were found to be proportionate to the size of their skulls, similar to those of present-day lizards, indicating that their teeth were not too large to be concealed by lips. Additionally, the arrangement of tiny openings near the jaws that provide blood and nerves to the gums and tissues surrounding the mouth seemed to resemble that of lizards rather than crocodiles in dinosaurs.

Co-author Dr. Mark Witton from the University of Portsmouth said, “Dinosaur artists have gone back and forth on lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s. They were then deeply rooted in popular culture through films and documentaries—Jurassic Park and its sequels, Walking with Dinosaurs and so on.”[3]

The discoveries may have an effect on our comprehension of dinosaur dental structure, eating habits, mechanical properties, and how they are depicted in both academic and mainstream media.[0] The teeth are mostly hidden by soft tissue as this Tyrannosaurus rex gulps down a juvenile Edmontosaurus, and a chubby-lipped T. rex swallowing its prey.

Although the study does not say that no extinct animals had exposed teeth, the researchers point out that some, like saber-toothed carnivorous mammals or marine reptiles and flying reptiles with extremely long, interlocking teeth, almost certainly did.[4] However, the study reveals that, at least in this respect, T. rex was more like lipped lizards than alligators or birds, and that the lips on dinosaurs would be similar to mobile lips that humans have.[5]

“Paleontologists often like to compare extinct animals to their closest living relatives, but in the case of dinosaurs, their closest relatives have been evolutionarily distinct for hundreds of millions of years and today are incredibly specialized,” said study co-author Derek Larson, Collections Manager and Researcher in Paleontology at the Royal BC Museum in Canada.[4] The similarity between theropod teeth and monitor lizards is astounding. Despite differences in size, from the tiny dwarf monitor to the massive Komodo dragon, their teeth share a common function. This likeness in function allows for favorable comparisons between extinct theropod dinosaurs and monitor lizards, despite their lack of close relation.[2]

In conclusion, the new study challenges previous perceptions of the appearance and oral anatomy of such iconic prehistoric predators, emphasizing the need for continued research and revision of our understanding of dinosaurs.[0]

0. “Deadly Teeth of T. rex Were Hidden Behind Scaly Lips, Shattering Prehistoric Perceptions” SciTechDaily, 30 Mar. 2023,

1. “Tyrannosaurus rex had lips over its teeth, research suggests” The Guardian, 30 Mar. 2023,

2. “‘Jurassic Park' wrong? T. rex had big lips that covered its fierce teeth” Study Finds, 30 Mar. 2023,

3. “T rex's ‘ferocious' fangs were hidden by lizard-like lips, say scientists” The Independent, 30 Mar. 2023,

4. “Did the T. rex have lips? New findings with B.C. co-author says yes” Global News, 30 Mar. 2023,

5. “T.Rex did NOT have exposed teeth – it had scaly, lizard-like LIPS” Daily Mail, 30 Mar. 2023,

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