Inside the jaws of the tyrant king

With 3D models revealing new secrets, Hady George explores how this cutting-edge technology will expand our knowledge of the appearance and behaviour of the formidable Tyrannosaurus rex.

You wouldn’t want to come face-to-face with a Tyrannosaurus rex. A skull over a metre and a half in length, bone-crushing jaws lined with railroad-spike teeth, and enormous eyes that stare forward toward anyone unlucky enough to fall under its gaze.

A team led by Florian Bouabdellah, a graduate of the University of Montpellier, got a good close-up of the jaws of a T. rex. Fortunately for them, this wasn’t a living T. rex but instead a digital restoration of a fossil skull generated using cutting-edge technology at the University of Witwatersrand in Johannesburg.

Digitally reconstructing fossils has revolutionised palaeontology. By processing over a thousand CT scans of a fossil T. rex skull, 3D models can be generated using state-of-the-art software.

The models allow scientists to see the insides of fossils by simply moving them about and editing them on a computer. They also allow visualisation of soft tissues such as sinus cavities, the brain, and even bony canals that blood vessels and nerves flow through to supply organs.

The team of scientists used these same techniques to get a detailed depiction of three major canals that run through the jaws in order to better understand the anatomy of T. rex, how sensitive the snout was, and whether the beast had fleshy lips covering its formidable teeth.

T. rex had the same three bony canals we have in our faces, a result of our common ancestry dating back over 300 million years.

The first canal runs around the eyes, the second travels across the upper jaw, and the third passes through the lower jaw. These canals house blood vessels and the trigeminal nerve which emerges from the back of the brain and splits into three parts, each division dedicated to one of these bony canals. The trigeminal nerve transmits signals that flex face muscles as well as sensations of touch and pain to the brain.

The scientists discovered some unique quirks of the canals of T. rex.

All three canals split into an extraordinary number of branches all over the jaws so they can supply those powerful crunching muscles, acute sensory organs, and possibly even colourful skin with sufficient blood and nerve endings. The branching around the roots of the terrifying teeth is especially intense, indicating a large amount of nutrients and energy were dedicated to sustaining the growth of new teeth throughout the lifetime of the animal.

The majority of the canals and their branches are clear in the 3D model the scientists generated, but there is ambiguity as to the branches within the tip of the snout. At the moment, it’s a mystery which of the three canals these branches originate from.

No Crocodile Smile

Modern crocodiles have astounding facial sensitivity that allows them to detect the subtlest of disturbances to the water they ambush in. Previously, it had been suggested that carnivorous dinosaurs like T. rex had similar facial sensitivity. By combining results from their own research and reviewing the research of others, the team led by Bouabdellah concluded that while carnivorous dinosaurs had dense canal branching, it still wasn’t as intense as that of crocodiles. From this conclusion, they inferred that most carnivorous dinosaurs, including T. rex, likely didn’t have facial sensitivity equivalent to that of crocodiles.

Did dinosaurs have lips?

Determining the presence of lips in dinosaurs has historically been challenging since lips don’t fossilise.

Previous research attempted to use the canal branching patterns in dinosaurs as evidence for lips, but Bouabdellah and their colleagues disagree with this. They instead point out issues with this reasoning, such as not considering the beaks of many dinosaurs, and suggest that we simply can’t make any firm conclusions about lips on dinosaurs as we currently don’t have any data or methods which would provide an end to this palaeo-puzzle.

This new insight into T. rex expands our knowledge of its anatomy and lifestyle. Further research could uncover more about the biology of T. rex, and we need to scan and create more 3D models of various types of dinosaurs if we are to better understand their evolution of sensory organs and soft-tissues. It’s this kind of exciting research that changes the way we think of dinosaurs, from terrifying monsters to living, breathing animals.

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