The findings change perceptions of the appearance and oral anatomy of tyrannosaurs
Forget jurassic park. Contrary to what we believed for over a century, the large teeth of Tyrannosaurus rex and other theropod dinosaurs probably did not protrude, but they were fully covered from thin, scaly lips when their mouths were closed, like lizards (center photo), according to a new study published in the journal Science.
The findings change our understanding of the appearance and oral anatomy of these iconic prehistoric animals.
Theropods are known for their large dagger-like teeth and scientific and popular reconstructions of them have often shown these teeth as exposed, protruding prominently from their closed mouths, as in crocodiles, rather than covered by soft oral tissues, as in most other terrestrial reptiles. However, theropod teeth are known to have relatively thin enamel, and since large theropod species likely retained their sharp and jagged teeth for long periods of time, the researchers believe that continued exposure would likely lead to tooth wear.
To test alternative hypotheses for theropod facial reconstructions, researcher Thomas Cullen of Auburn and Carleton Universities and the Field Museum of Natural History and colleagues evaluated the relationship between skull length and tooth size of different theropods, as well as living and extinct toothed reptiles. They also performed a comparative histological analysis of the wear patterns of tyrannosaurus and crocodile teeth.
As they observed, unlike their closest crocodilian relatives, theropods’ teeth they had no signs of wear on the outer surface and this indicates the existence of extraoral tissues and oral secretions required to keep the teeth hydrated and protected from exposure. In addition, the researchers found that although the skulls and teeth of some theropods were much larger than extant reptiles, the tooth-skull size relationship in theropods is in close agreement with that of living reptiles, particularly large lizards, which do not they have exposed teeth. These findings suggest that theropods’ teeth were not too large to fit in their mouths.
Source: Skai
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