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Jurassic Park Got It Wrong: T. Rex Had Scaly Lips Covering Its Teeth

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New insights into dinosaur ecology and evolution: Predatory dinosaurs had lizard-like lips, not exposed teeth

According to a recent study, it appears that predatory dinosaurs, including the well-known Tyrannosaurus rex, did not have teeth that were constantly exposed like in movies like Jurassic Park. Instead, they had lips that were covered in scales, resembling those of lizards, which served to close and protect their mouths.

The debate about whether theropod dinosaurs, a group that includes carnivorous and dominant species like T. rex and Velociraptor, as well as birds, had mouths without lips, in which the upper teeth were constantly visible above the lower jaw like in crocodiles, has been a topic of discussion among researchers and artists.

A team of international researchers has challenged some of the commonly held beliefs about the appearance of predatory dinosaurs, arguing that these creatures possessed lips similar to those of lizards and their close relatives, the tuatara. The tuatara is a rare reptile found exclusively in New Zealand, which is the only surviving member of a reptilian order that thrived during the age of the dinosaurs.

Jurassic Park Got It Wrong: T. Rex Had Scaly Lips Covering Its Teeth
Jurassic Park Got It Wrong: T. Rex Had Scaly Lips Covering Its Teeth

In the most comprehensive investigation of this topic to date, the researchers analyzed the structure of teeth, patterns of wear, and jaw morphology in reptile groups with and without lips. They discovered that the anatomy and functionality of theropod mouths were more similar to those of lizards than crocodiles.

As a result, it appears that these dinosaurs had oral tissues resembling those of lizards, including scaly lips that covered their teeth.

It is unlikely that these lips were muscular, as is the case in mammals. Typically, reptilian lips cover their teeth, but lack the ability to move independently, and therefore cannot form the types of expressions or movements that we associate with lips in humans or other mammals.

According to study co-author Derek Larson, who is also a Collections Manager and Researcher in Palaeontology at the Royal BC Museum in Canada, “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 specialised.

From Jurassic Park to Science Fact: New Study Reveals T. rex Had Lizard-Like Lips
From Jurassic Park to Science Fact: New Study Reveals T. rex Had Lizard-Like Lips

“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 favourably with extinct animals like theropod dinosaurs based on this similarity of function, even though they are not closely related.”

Dr. Mark Witton, co-author of the study and a researcher at the University of Portsmouth, notes that the depiction of dinosaur lips has been a topic of debate among artists and scientists since the 19th century. In the 1980s and 1990s, depictions of lipless dinosaurs became more common in popular culture through movies and documentaries such as Jurassic Park and Walking with Dinosaurs.

However, Dr. Witton suggests that this shift towards lipless dinosaurs was likely driven more by a preference for a new, more fearsome-looking aesthetic than by any scientific discoveries or studies. The recent study overturns this popular view, proposing instead that these dinosaurs had lizard-like lips that covered their teeth. As a result, many of the most iconic depictions of dinosaurs, including the T. rex in Jurassic Park, are likely to be inaccurate.

New Study Says Predatory Dinosaurs Had Scaly Lips, Not Exposed Teeth
New Study Says Predatory Dinosaurs Had Scaly Lips, Not Exposed Teeth

According to the study published in the journal Science, tooth wear in lipless animals differed significantly from that observed in carnivorous dinosaurs. The study also indicated that the size of dinosaur teeth, relative to skull size, was similar to that of modern lizards, suggesting that they were not too large to be covered by lips.

Additionally, small holes located around the jaws that provide nerves and blood to the gums and tissues around the mouth were found to be more similar to those in lizards than in crocodiles.

The study further revealed that when the jaws of lipless theropods were modeled during mouth closure, the lower jaw had to either crush the jaw-supporting bones or dislocate the jaw joint in order to seal the mouth.

According to Kirstin Brink, Assistant Professor of Palaeontology at the University of Manitoba and co-author of the study, saliva plays a crucial role in maintaining dental health.

Jaws Drop as New Study Challenges Popular Depictions of Lipless Dinosaurs
Jaws Drop as New Study Challenges Popular Depictions of Lipless Dinosaurs

Uncovered teeth are at risk of drying out and can be more easily damaged during feeding or fighting, similar to what is observed in crocodiles but not in dinosaurs. Brink also explained that dinosaur teeth have thin enamel, whereas mammal teeth typically have thicker enamel (with some exceptions).

Crocodile enamel is thicker than dinosaur enamel but not as thick as mammalian enamel. However, some groups of mammals have exposed enamel, but their enamel is adapted to withstand exposure.

“Although it’s been argued in the past that the teeth of predatory dinosaurs might be too big to be covered by lips,” adds lead author Thomas Cullen, “our study shows that, 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 that their teeth were too big to cover with lips.”

The findings from the study offer fresh perspectives on how we can reconstruct the soft tissues and physical characteristics of extinct species such as dinosaurs. These insights can provide valuable information on their feeding habits, dental health maintenance, as well as their overall evolution and ecological patterns.

Study Finds T. rex Had Lizard-Like Lips
Study Finds T. rex Had Lizard-Like Lips

According to Dr. Witton, there are some who believe that we have limited knowledge about the physical appearance of dinosaurs, except for basic features such as the number of fingers and toes. However, studies such as the one conducted by his team demonstrate that we have a better understanding of many aspects of dinosaur appearance.

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

The researchers note that their study does not claim that no extinct animals had visible teeth. In fact, they acknowledge that certain species, such as sabre-toothed carnivorous mammals, or marine and flying reptiles with interlocking teeth, almost certainly had exposed teeth.

Source: 10.1126/science.abo7877

Image Credit: Mark Witton

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