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HomeSciencePredatory dinosaurs, like T. Rex, had lizard-like lips

Predatory dinosaurs, like T. Rex, had lizard-like lips

A new study suggests that predatory dinosaurs, such as Tyrannosaurus rex, did not have permanently exposed teeth as depicted in movies like Jurassic Park, but instead had scaly, lizard-like 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 such as T. rex and Velociraptor, as well as birds, had lipless mouths where permanently visible upper teeth hung above its lower jaws, similar to the mouth of a crocodile.

However, an international team of researchers questions 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 the dinosaurs.

In the most detailed study to date on this topic, the researchers examined the tooth structure, wear patterns, and jaw morphology of the lipped and non-labiated groups of reptiles and found that the anatomy and functionality of the mouth of theropods resembles that of lizards more than that of crocodiles. This implies lizard-like buccal tissues, including the scaly lips that covered its teeth.

These lips were probably not muscular, as in mammals. Most reptile lips cover the teeth, but they cannot move independently: they cannot curl back in a snarl 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: “Palaeontologists often like to compare extinct animals with their closest living relatives, but in the case of Dinosaurs, their closest relatives, have been evolutionarily distinct for hundreds of millions of years, and today they are incredibly specialized.”

“It’s amazing how similar theropod teeth are to those of monitor lizards. From the smallest dwarf monitor to the Komodo dragon, teeth work in much the same way. Thus, monitors can be compared very favorably to extinct animals such as theropod dinosaurs based on this similarity in function, even though they are not closely related.”

Co-author Dr Mark Witton, from 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. Then they were deeply embedded in popular culture through movies and documentaries: Jurassic Park and its sequels, Walking with Dinosaurs, etc.

“Interestingly, there was never a specific study or discovery that instigated this change and, to a large extent, it likely reflected a preference for a new fierce-looking aesthetic rather than a change in scientific thinking. We are changing this popular representation by covering your 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 lipless animals was markedly different from that seen in carnivorous dinosaurs and that dinosaur teeth were no larger, relative to skull size, than in carnivorous dinosaurs. than those of modern lizards, implying that they were not too large to cover with lips.

In addition, the distribution of the small openings around the jaws, which supply nerves and blood to the gums and tissues surrounding the mouth, was more lizard-like in dinosaurs than crocodiles. Furthermore, modeling of the mouth closure of the jaws of lipless theropods demonstrated that the lower jaw had to either crush the supporting bones of the jaw or disarticulate the jaw joint to seal the mouth.

“As any dentist will tell you, saliva is important for maintaining healthy teeth. Teeth not covered by the lips are at risk of drying out and may suffer further damage 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.

And he adds: «The teeth of dinosaurs have a very fine enamel and those of mammals, thick (with some 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 do have exposed enamel, but their enamel is modified to withstand 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 predatory dinosaur teeth might be too large to be covered by lips, our 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 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 fed, how they maintained their dental health, and more general patterns of their evolution and ecology.

According to Dr. Witton: ‘Some say we have no idea what dinosaurs look like beyond basic traits 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 what dinosaurs looked like. Far from being clueless, we can now say “oh, doesn’t that have lips? Or a certain type of scales or feathers? So it’s as realistic a representation of that 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.


Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology



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