Predatory dinosaurs like T. Rex did not boast teeth

March 31 () –

A new study suggests that predatory dinosaurs, such as Tyrannosaurus rex, did not have permanently exposed teeth as depicted in movies like ‘Jurassic Park’.

Instead, they had scaly, lizard-like lips that covered and sealed their mouths, the researchers report in the journal ‘Science’.

Researchers and artists have debated whether theropod dinosaurs, the group of bipedal dinosaurs that includes carnivores and top predators such as T. rex and Velociraptor, as well as birds, had lipless mouths where perpetually visible upper teeth hung above their lower jaws. , similar to the mouth of a crocodile.

However, an international team of researchers is now challenging some of the best-known representations, claiming that these dinosaurs had lips resembling those of lizards and those of their 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 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 involves lizard-like mouth tissues, including the scaly lips that cover their teeth.

These lips were probably not muscular, as in mammals. Most reptile lips cover their teeth, but they cannot move independently: they cannot bend back in a growl or perform other movements that we associate with human or other mammalian lips.

Study co-author Derek Larson, Director of Collections and Research Palaeontology at the Royal British Columbia Museum (Canada), points out it’s a statement that “to paleontologists they 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,” he continues. “From the smallest dwarf monitor to the Komodo dragon, teeth function in much the same way. So monitors can compare very favorably with extinct animals such as theropod dinosaurs based on this similarity of functions, even if they are not closely related“.

Co-author Dr Mark Witton, from the University of Portsmouth, UK, comments: “Dinosaur artists have come and gone on lips since we started restoring dinosaurs in the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s. They then became deeply entrenched in popular culture through movies and documentaries: ‘Jurassic Park’ and its sequels, ‘Walking with Dinosaurs,’ and so on.”

“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,” he says. “We are changing this popular representation covering its teeth with lizard lips.This means that many of our favorite representations of dinosaurs are incorrect, including the iconic T. rex from ‘Jurassic Park.'”

The results found that tooth wear in lipless animals was markedly different from that observed in carnivorous dinosaurs and that dinosaur teeth were no larger, relative to skull size, 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. Modeling of the mouth closure of the jaws of lipless theropods showed that the lower jaw had to 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 in maintaining the health of teeth. Teeth not covered by lips are at risk of drying out and can suffer further damage during eating or fighting, as we see in crocodiles, but not in dinosaurs“, explains co-author Kirstin Brink, Assistant Professor of Paleontology at the University of Manitoba (Canada).

As he points out, “dinosaur teeth have very fine enamel and mammalian teeth have thick (with a few exceptions). Crocodile enamel is slightly thicker than dinosaur tooth, but not as thick as tooth enamel.” Mammals There are some groups of mammals that do have exposed enamel, but its enamel is modified to withstand exposure.”

For his part, Thomas Cullen, Assistant Professor of Paleobiology at Auburn University (United States) and lead author of the study, says that, “although in the past it has been argued that the teeth of predatory dinosaurs could be too large to be covered by the lips, the study shows that their teeth were not, in fact, uncharacteristically large.”

“Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards when compared by skull size, which rejects the idea that her teeth were too big to cover with her lips“, he highlights.

The results provide new insights into how we reconstruct soft tissue and what dinosaurs and other extinct species looked like. This can provide crucial information about how they fed, how they maintained their dental health, and the broader 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 increasingly understanding many aspects of what dinosaurs look like“.

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.