Fifty Shades of Rex: Reconstructing Colour in Tyrannosaurus

Last year I saw a concept “T. rex leather” handbag (see image 1), that got me thinking about what real T. rex skin would look like, specifically its colour. When I looked into dinosaur colour, I realized that there are shockingly few dinosaurs that we actually know the colour of (only about 9) (see image 2). Colour and pattern is a vital part in understanding an animals environment and behaviour, being directly impacted by its needs for both. So if you can assess these impacts on your chosen animal, the most efficient colour can be inferred. But I decided to use anatomical constraints as well as ecological to estimate the general colouration of Tyrannosaurus rex. This could help in media and scientific depictions of the animal to give it a more consistent and accurate appearance.

To find T. rex’s colour I needed to use modern animals for comparison since we don’t have any direct evidence. First I created a probability model based on ground birds and the frequency of pigments in a similar habitat to T. rex. Then I found the likelihood of certain pigments coming from its diet (carotenoids - only synthesized in plants) and the energy they would take to store. But for the pigments that can be synthesized in animals I found the energy usage for that synthesis to assess efficiency. Lastly I created a vision model for T. rex’s prey and found how well each pigment could camouflage in their eyes.

I found that eumelanin (See image 1),the cause of brown, would have been the most efficient pigment to synthesize in a large theropod like T. rex. It is also found very commonly in terrestrial birds in a similar environment to the T. rex’s habitat (See image 2). But when applied to the prey eyesight test I found that Pheomelanin would have been the most effective pigment for camouflage. So it can be inferred that T. rex would have been primarily brown with a lighter beige underbelly or patterning.

These results can be applied to T. rex depictions in scientific media to create a more unified and accurate appearance. The general procedure can also be used with minor adjustments for other large theropods and any extinct animal with more major changes.

If I were to improve my project I may delve further into the sexual selection aspect of colouration. Colours and patterns are often used by modern birds for mate selection and display, which could have been a factor in T. rex’s pigment. This general process could also be applied to a number of other extinct animals, with minor changes of course.

I would like to acknowledge Britannica and the Animal Diversity Web for helping greatly in finding information on crocodilian species, particularly the lesser-known ones. Also, the teams behind the documentaries ‘Walking With Dinosaurs’ and ‘Prehistoric Planet’ for introducing me to and providing new information respectively on dinosaurs. As well, the former fossil vertebrate collection manager at the Chicago Field Museum, Dr. William Simpson, for providing a tour of the archives and letting us in to see Sue the T. rex for free and Dr. Jakob Vinther for providing great feedback on my work. I would also like to thank my cousins Jacob Dixon, for helping me film my video, and Ethan Kucher who is in the aerospace category (check out his project!). Finally, I want to give a big thanks to my parents for indulging me in my years long dinosaur addiction and always giving their support.

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