Deadly Teeth of T. rex Were Hidden Behind Scaly Lips, Shattering Prehistoric Perceptions

Tyrannosaurus Lipped Mouth

Revealed: The Secrets our Clients Used to Earn $3 Billion

A juvenile Edmontosaurus disappears into the large, lipped mouth of Tyrannosaurus. Credit: Mark Witton

A brand new examine challenges the long-held perception that enormous theropod dinosaurs, together with Tyrannosaurus rex, had uncovered enamel when their mouths had been closed. Instead, the analysis suggests their enamel had been coated by skinny, scaly lips, just like fashionable Komodo dragons. The findings might affect our understanding of dinosaur dental anatomy, feeding ecology, biomechanics, and their portrayal in scientific and common tradition.

Contrary to greater than a century of scientific and common depictions, the big enamel of Tyrannosaurus rex and different toothy theropod dinosaurs had been probably utterly coated by skinny, scaly “lips” when the mouth was closed. This is in keeping with a brand new examine printed at present (March 30) within the journal Science. The findings shift perceptions in regards to the look and oral anatomy of such iconic prehistoric predators.

Nonavian theropod dinosaurs are famend for his or her giant, dagger-like enamel. As a outcome, scientific and common reconstructions of those dinosaurs have typically featured these enamel as uncovered – prominently protruding outdoors their closed mouths like crocodiles – fairly than coated by delicate facial tissues of the mouth as they’re in most different terrestrial reptiles, like fashionable Komodo dragons.

T. rex Juvenile Running

A half-grown Tyrannosaurus, sporting a full set of lips, runs down Struthiomimus, a beaked ostrich dinosaur. Credit: Mark Witton

However, theropod enamel are recognized to have comparatively skinny enamel. Since giant theropod species likely retained their sharp and serrated teeth over long periods of time, it’s thought that constant exposure would likely lead to damaging tooth desiccation and wear. Whether these ancient apex predators’ teeth were permanently exposed, as is often depicted, or covered by lip-like labial scales like a Komodo dragon, remains uncertain.

To test alternate hypotheses of theropod facial reconstructions, Thomas Cullen and colleagues evaluated the relationship between skull length and tooth size for a range of theropod dinosaurs and living and extinct toothed reptiles. They performed a comparative histological analysis of tooth wear patterns for tyrannosaurid and crocodilian teeth.

Tyrannosaurus rex Bellowing

Tyrannosaurus rex bellowing with its mouth shut, like a vocalising alligator. With its mouth closed, all of the enormous teeth of T. rex would be invisible behind its lips. Credit: Mark Witton

According to Cullen et al., in contrast to their closest toothed crocodilian relatives, theropod teeth lacked any evidence of outer surface wear, indicating the existence of extraoral tissues and oral secretions needed to keep them hydrated and protected from exposure. What’s more, the authors found that, even though the skulls and teeth of some theropods were far larger than extant reptiles, the tooth-skull size relationship in theropods closely aligned with that of living reptiles, particularly monitor lizards, who do not have exposed teeth.

These findings suggest that theropod teeth were not too big to fit in their mouth without having to be exposed. Cullen et al. argue that the data suggests that all theropod dinosaurs had teeth completely 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 portrayal of dinosaurs in science and popular culture.

Theropods Lips Infographic

A one-sheet summary of the main investigations and conclusions of the study. Credit: Mark Witton

Reference: “Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology” 30 March 2023, Science.
DOI: 10.1126/science.abo7877