Many of the graphic representations created in recent years to portray the supposed image of predatory dinosaurs such as the Tyrannosaurus rex (Tyrannosaurus rex), including the Jurassic Park film saga, show these late Cretaceous carnivores with their jaws half-open, showing a wide collection of teeth, up to 30 centimeters in length. Fossils recovered to date show the appearance that the teeth of these dinosaurs were visible at all times, but a new study calls this supposed figure into question.
In a study led by experts from the universities of Auburn and Portsmouth (United States) whose results are published in the journal Science (March 30), data is provided that suggests that, in reality, these carnivorous dinosaurs did not have their teeth exposed in any way. permanent, but they had scaly lips, like those of a lizard, that covered and covered their mouths.
If the images of T. rex and Velociraptor until now were of animals without lips, with the upper teeth perpetually visible, in the style of many crocodile species, the new study considers that these dinosaurs had lips similar to those of lizards and its relative, the tuatara, a rare reptile found only in New Zealand; that they are the last survivors of an order of reptiles that thrived in the age of the dinosaurs.
In the present study, the most detailed study of this problem to date, it has led researchers to examine the tooth structure, wear patterns, and jaw morphology of lipped and lipless groups of reptiles. Thus they discovered that the anatomy and functionality of the theropod mouth is more similar to that of lizards than to that of crocodiles. This involves lizard-like oral tissues, including the scaly lips that cover its teeth.
The authors acknowledge that the lips of tyrannosaurs were possibly not muscular, like those of mammals. Most reptile lips cover their teeth, but they cannot move independently: they cannot curl back in a growl or make other types of movements that we associate with the lips of humans and other mammals.
To date, there has been no study or discovery dedicated to this type of facial detail and, to a large extent, the representations are likely to be of interest in highlighting the ferocity of these prehistoric animals, without a solid scientific basis. “We are changing this popular representation by covering its teeth with lizard lips. This means that many of our favorite dinosaur representations are incorrect, including the iconic Tyrannosaurus from Jurassic Park,” explains Mark Witton, co-author of the study published in Science.
Derek Larson, also a co-author of the study, as well as a paleontology researcher at the Royal BC Museum in Canada, says: “Paleontologists often like to compare extinct animals with their closest living relatives, but in the case of dinosaurs, their relatives The closest ones have been evolutionarily distinct for hundreds of millions of years, and today they are incredibly specialized.”
“It’s quite remarkable how similar theropod teeth are to monitor lizards. From the smallest dwarf monitor to the Komodo dragon, teeth work the same way. Therefore, monitors compare quite favorably to extinct animals such as theropod dinosaurs based on this similarity in function, even though they are not closely related,” Larson said.
The authors of the new study found that tooth wear in lipless animals was markedly different from that seen in carnivorous dinosaurs and that dinosaur teeth were no larger, relative to skull size, than those of dinosaurs. modern lizards, which implies that they were not very large. cover with lips
Furthermore, the distribution of small holes around the jaws, which supply nerves and blood to the gums and tissues around the mouth, was more like that of a lizard in dinosaurs than that of a crocodile. In addition, modeling of the mouth closure of the jaws of lipless theropods showed that the lower jaw had to either crush the jaw-supporting bones or disarticulate the jaw joint to seal the mouth.
“As any dentist will tell you, saliva is important in maintaining the health of your teeth. Teeth not covered by the lips are at risk of drying out and can be further damaged during feeding or fighting, as we see in crocodiles, but not in dinosaurs,” said co-author Kirstin Brink, an assistant professor of paleontology at the University of Manitoba.
“Dinosaur teeth have very thin enamel and mammalian teeth have thick enamel (with a few exceptions). Crocodile enamel is slightly thicker than dinosaur enamel, but not as thick as mammal enamel. There are some groups of mammals that have exposed enamel, but their enamel is modified to resist exposure, â€Brink details in a note released by his university.
Thomas Cullen, Assistant Professor of Paleobiology at Auburn University and lead author of the study, explains that “although it has been argued in the past that the teeth of predatory dinosaurs might be too large to cover with their lips, the new study shows that Actually, his teeth weren’t uncharacteristically large.” “Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards compared to the size of the skull, rejecting the idea that their teeth were too large to cover with their lips,” explains Thomas Cullen.
