A brand-new research study challenges the long-held belief that big theropod dinosaurs, including Tyrannosaurus rex, had actually exposed teeth when their mouths were closed. Rather, the research study suggests their teeth were covered by thin, scaly lips, similar to contemporary Komodo dragons. Theropod teeth are understood to have reasonably thin enamel. Since large theropod species likely kept their serrated and sharp teeth over long periods of time, its believed that constant direct exposure would likely lead to damaging tooth desiccation and wear. With its mouth closed, all of the massive teeth of T. rex would be unnoticeable behind its lips.
A half-grown Tyrannosaurus, sporting a full set of lips, runs down Struthiomimus, a beaked ostrich dinosaur. Credit: Mark Witton
Nevertheless, theropod teeth are known to have fairly thin enamel. Given that large theropod types likely kept their sharp and serrated teeth over extended periods of time, its believed that constant exposure would likely lead to damaging tooth desiccation and wear. Whether these ancient pinnacle predators teeth were permanently exposed, as is frequently illustrated, or covered by lip-like labial scales like a Komodo dragon, remains uncertain.
To test alternate hypotheses of theropod facial restorations, Thomas Cullen and associates assessed the relationship in between skull length and tooth size for a series of theropod dinosaurs and living and extinct toothed reptiles. They carried out a relative histological analysis of tooth wear patterns for tyrannosaurid and crocodilian teeth.
Tyrannosaurus rex wailing with its mouth shut, like a vocalising alligator. With its mouth closed, all of the massive teeth of T. rex would be unnoticeable behind its lips. Credit: Mark Witton
According to Cullen et al., in contrast to their closest toothed crocodilian loved ones, theropod teeth lacked any proof of external surface area wear, indicating the presence of oral secretions and extraoral tissues required to keep them hydrated and secured from exposure. Whats more, the authors discovered that, even though the skulls and teeth of some theropods were far larger than extant reptiles, the tooth-skull size relationship in theropods carefully lined up with that of living reptiles, especially monitor lizards, who do not have exposed teeth.
These findings suggest that theropod teeth were not too huge to fit in their mouth without needing to be exposed. Cullen et al. argue that the data suggests that all theropod dinosaurs had actually teeth totally covered by labial scales when the mouth was closed– findings that could have implications on our understanding of dinosaur dental anatomy, feeding ecology, and biomechanics, as well as on the representation of dinosaurs in science and popular culture.
A one-sheet summary of the main examinations and conclusions of the study. Credit: Mark Witton
Recommendation: “Theropod dinosaur facial reconstruction and the value of soft tissues in paleobiology” 30 March 2023, Science.DOI: 10.1126/ science.abo7877.
A juvenile Edmontosaurus vanishes into the enormous, lipped mouth of Tyrannosaurus. Credit: Mark Witton
A new study challenges the long-held belief that big theropod dinosaurs, consisting of Tyrannosaurus rex, had exposed teeth when their mouths were closed. Instead, the research recommends their teeth were covered by thin, scaly lips, similar to modern-day Komodo dragons. The findings might affect our understanding of dinosaur oral anatomy, feeding ecology, biomechanics, and their portrayal in popular and clinical culture.
Contrary to more than a century of popular and scientific depictions, the big teeth of Tyrannosaurus rex and other toothy theropod dinosaurs were most likely totally covered by thin, scaly “lips” when the mouth was closed. This is according to a new study released today (March 30) in the journal Science. The findings move understandings about the look and oral anatomy of such renowned ancient predators.
Nonavian theropod dinosaurs are renowned for their large, dagger-like teeth. As an outcome, scientific and popular restorations of these dinosaurs have actually typically included these teeth as exposed– plainly protruding outside their closed mouths like crocodiles– rather than covered by soft facial tissues of the mouth as they remain in many other terrestrial reptiles, like contemporary Komodo dragons.