T. rex had big lips that covered its sharp, jagged teeth

By Mark Waghorn via SWNS

T Rex had big lips that covered its sharp, jagged teeth, according to new research.

Depictions in films such as Jurassic Park that make it look more fierce are wrong, say scientists.

Predatory dinosaurs had scaly, lizard-like kissers that would have kept its mouth shut - most of the time.

An international team examined the tooth structure, wear patterns and jaw shapes of lipped and lipless reptile groups.

They found mouth anatomy and function of the meat-eating theropods, which includes T Rex, resembled lizards more than crocodiles.

Co-author Dr. Mark Witton, of the University of Portsmouth, said: "Dinosaur artists have gone back and forth on lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s.

"They were then deeply rooted in popular culture through films and documentaries — Jurassic Park and its sequels, Walking with Dinosaurs and so on.

"Curiously, there was never a dedicated study or discovery instigating this change and, to a large extent, it probably reflected preference for a new, ferocious-looking aesthetic rather than a shift in scientific thinking.

"We're upending this popular depiction by covering their teeth with lizard-like lips. This means a lot of our favorite dinosaur depictions are incorrect, including the iconic Jurassic Park T Rex."

T Rex and his fellow theropods such as Velociraptor would not have teeth that stick out even when their mouths are closed unlike reproductions in movies - and even museums.

Only a few land animals such as elephants and wild boars have exposed teeth - and these have no enamel.

Co-author Dr. Kirstin Brink, of the University of Manitoba, Canada, said: "Dinosaur teeth have very thin enamel and mammal teeth have thick enamel - with some exceptions.

"Crocodile enamel is a bit thicker than dinosaur enamel, but not as thick as mammalian enamel. There are some mammal groups that do have exposed enamel, but their enamel is modified to withstand exposure."

The idea top predators like T Rex and Velociraptor had mouths where perpetually visible upper teeth hung over their lower jaws - similar to the mouth of a crocodile - has been debated for decades.

The most detailed study of its kind to date now shows their lips were similar to those of lizards and their relative, the tuatara - a rare reptile found only in New Zealand.

They are the last survivors of an order that thrived in the age of the dinosaurs.

Unlike mammals, they were not muscular. Most reptile lips cover the teeth but cannot be moved independently - they cannot be curled back into a snarl, or make other sorts of movements we associate with lips in humans.

Co-author Dr. Derek Larson, of the Royal BC Museum in Canada, said: "Palaeontologists often like to compare extinct animals to 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 are incredibly specialized.

"It’s quite remarkable how similar theropod teeth are to monitor lizards. From the smallest dwarf monitor to the Komodo dragon, the teeth function in much the same way.

"So, monitors can be compared quite favorably with extinct animals like theropod dinosaurs based on this similarity of function, even though they are not closely related."

The analysis in the journal Science found tooth wear in lipless animals was markedly different from that seen in carnivorous dinosaurs. Dinosaur teeth were no larger, relative to skull size, than those of modern lizards, implying they were not too big to cover with lips.

Also, the distribution of small holes around the jaws, which supply nerves and blood to the gums and tissues around the mouth, were more lizard-like in dinosaurs than crocodile-like.

Furthermore, modeling mouth closure of lipless theropod jaws showed that the lower jaw either had to crush jaw-supporting bones or disarticulate the jaw joint to seal the mouth.

Dr. Brink said: "As any dentist will tell you, saliva is important for maintaining the health of your teeth.

"Teeth that are not covered by lips risk drying out and can be subject to more damage during feeding or fighting, as we see in crocodiles, but not in dinosaurs."

T Rex having lips has scientific implications for how it and other theropods chewed and processed food.

Lead author Dr. Thomas Cullen, of Auburn University in Alabama, said: "It has been argued in the that the teeth of predatory dinosaurs might be too big to be covered by lips.

"Our study shows, in actuality, their teeth were not atypically large. Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards when compared for skull size, rejecting the idea their teeth were too big to cover with lips"”

The results provide new insights into how we reconstruct the soft tissues and appearance of dinosaurs and other extinct species.

This can give crucial information on how they fed, how they maintained their dental health and the broader patterns of their evolution and ecology.

Added Dr. Witton: "Some take the view we are clueless about the appearance of dinosaurs beyond basic features like the number of fingers and toes.

"But our study, and others like it, show we have an increasingly good handle on many aspects of dinosaur appearance.

"Far from being clueless, we are now at a point where we can say 'oh, that doesn't have lips? Or a certain type of scale or feather?’ Then that is as realistic a depiction of that species as a tiger without stripes."

It doesn't mean no extinct beasts had exposed teeth.

Some, like saber-toothed carnivorous mammals, or marine reptiles and flying reptiles with extremely long, interlocking teeth, almost certainly did.