A recent study regarding the cranial structure of Tyrannosaurus rex (T. rex) disputes over a century of both scientific and popular illustrations.
Non-avian theropod dinosaurs have long been known for their large, blade-like teeth. Consequently, these dinosaurs have often been depicted in popular and scientific reconstructions with their teeth prominently protruding from their closed mouths like crocodiles, instead of being concealed by soft oral tissues like most other terrestrial reptiles, such as the Komodo dragon.
However, the enamel on theropod teeth is relatively thin. Due to the fact that large theropod species likely retained their sharp, serrated teeth for extended periods, it has been assumed that perpetual exposure would lead to desiccation and tooth wear.
Whether the teeth of these ancient predators were consistently exposed as they are often depicted, or concealed by labial scales as in the case of the Komodo dragon, has long been uncertain.
In order to examine alternative hypotheses of facial reconstructions of theropods, a team of researchers led by Thomas Cullen of Auburn University in the United States and Mark Witton of the University of Portsmouth in the United Kingdom, evaluated the correlation between skull length and tooth size in various extinct theropod dinosaurs and toothed reptiles.
The researchers carried out a comparative histological analysis of tooth wear patterns in tyrannosaurid and crocodilian teeth.
According to Cullen and his colleagues, theropods had teeth without any external surface wear, in contrast to their closest toothed crocodilian relatives. This indicates that extraoral tissues and oral secretions were present to keep them hydrated and protected from exposure.
Moreover, the study authors found that despite the skulls and teeth of some theropods being significantly larger than those of extant reptiles, the relationship between skull-to-tooth size in theropods was closely aligned with that of living reptiles, specifically monitor lizards that do not have exposed teeth.
These discoveries imply that theropod teeth were not too large to fit inside their mouths without being exposed. Cullen and his colleagues contend that the data suggests that all theropod dinosaurs had teeth that were entirely covered by labial scales when their mouths were closed.
An artist’s rendering of what a typical Tyrannosaurus rex would have looked like in life, based on what was discovered in the new study. With his mouth closed, his terrifying teeth would be hidden behind his lips. (Image: Mark Witton)
The findings could have important implications for understanding dinosaur dental anatomy, feeding ecology, and the biomechanics of their eating actions, as well as for the graphic representation of dinosaurs in science and popular culture.
The study is titled “Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology”. And it has been published in the academic journal Science. (Source: AAAS)