A new study suggests that predatory dinosaurs such as Tyrannosaurus rex did not have permanently exposed teeth, as depicted in films such as Jurassic Park, but instead had lizard-like scaly lips that covered and sealed their mouths.
Researchers and artists have debated whether theropod dinosaurs, the group of bipedal dinosaurs that includes carnivores and large predators like T. rex and Velociraptor, as well as birds, had lipless mouths where the permanently visible upper teeth hung above their similar lower jaws. into the mouth of a crocodile.
However, an international team of researchers has questioned some of the best-known representations and claims that these dinosaurs had lips similar to those of lizards and their relative, the tuatara -a rare reptile found only in New Zealand-, which are the last survivors of an order of reptiles that thrived in the age of dinosaurs.
In the most detailed study to date on this topic, researchers examined the tooth structure, wear patterns, and jaw morphology of labiated and non-libated reptilian groups and found that the anatomy and functionality of the theropod mouth resembled that of of the lizards. more than crocodiles. This implies lizard-like mouth tissues, including the scaly lips that covered their teeth.
These lips were probably not muscular, as in mammals. Most reptilian lips cover their teeth, but they cannot move independently: they cannot curl up in a growl or perform other types of movements that we associate with the lips of humans or other mammals.
Study co-author Derek Larson, Director of Collections and Research Paleontology at the Royal Museum of British Columbia, Canada, said: “Paleontologists often like to compare extinct animals to their closest living relatives, but in the case of dinosaurs, their closest relatives, were evolutionarily distinct for hundreds of millions of years, and are now incredibly specialized.”
“It’s amazing how similar theropod teeth are to monitor lizards. From the smallest dwarf monitor to the Komodo dragon, the teeth work the same way. So monitors may compare very favorably with extinct animals such as theropod dinosaurs based on this similarity in function, even if they are not closely related.”
Co-author Dr. Mark Witton of the University of Portsmouth said: “Dinosaur artists have come and gone about lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s. were deeply embedded in popular culture through films and documentaries: Jurassic Park and its sequels, Walking with Dinosaurs, etc.
“Interestingly, there was never a specific study or finding that instigated this shift, and to a large extent, it likely reflected a preference for a fierce-looking new aesthetic rather than a shift in scientific thinking. We are changing this popular representation by covering the teeth with lizard lips. This means that many of our favorite depictions of dinosaurs are incorrect, including the iconic T. rex from Jurassic Park.”
The results, published in the journal Science, found that tooth wear in animals without lips was markedly different from that seen in carnivorous dinosaurs, and that dinosaur teeth were no larger, relative to skull size, than in carnivorous dinosaurs. that they were not too big to cover with the lips.
Furthermore, the distribution of the small openings around the jaws, which supply nerves and blood to the gums and tissues around the mouth, was more lizard-like in dinosaurs than in crocodiles. Furthermore, modeling the mouth closure of lipless theropod jaws demonstrated that the lower jaw had to crush the jaw-supporting bones or disarticulate the jaw joint to seal the mouth.
“As any dentist will tell you, saliva is important for keeping your teeth healthy. Teeth not covered by the lips are at risk of drying out and can suffer further damage during feeding or fighting, as we see in crocodiles but not dinosaurs,” said co-author Kirstin Brink, assistant professor of paleontology at the University of Manitoba.
And he adds: “Dinosaurs’ teeth have very thin enamel and mammalian teeth have thick enamel (with a few exceptions). Crocodile enamel is slightly thicker than that of dinosaurs, but not as thick as that of mammals. There are some groups of mammals that have exposed enamel, but their enamel is modified to resist exposure.”
Thomas Cullen, assistant professor of paleobiology at Auburn University and lead author of the study, said: “Although it has been argued in the past that the teeth of predatory dinosaurs may be too large to be covered by the labia, our study shows that, in fact, their teeth were not unusually large. Even the giant teeth of tyrannosaurs are proportionately similar in size to those of living predatory lizards when compared by skull size, disproving the idea that their teeth were too large to cover with their lips.”
The results provide new insights into how to reconstruct the soft tissues and appearance of dinosaurs and other extinct species. This can provide crucial information about how they ate, how they maintained their oral health, and more general patterns of their evolution and ecology.
According with the doctor. Witton: ‘Some say we have no idea what dinosaurs are like beyond basic features like the number of fingers and toes. But our study and others like it show that we are getting better at understanding many aspects of dinosaur appearance. Far from being ignorant, we can now say “oh, doesn’t that have lips? Or a certain type of scales or feathers? So it’s about as realistic a representation of this species as a tiger without stripes.”
The researchers note that their study does not claim that any extinct animals had exposed teeth: some, such as saber-toothed carnivorous mammals or marine and flying reptiles with extremely long, interlocking teeth, almost certainly did.