Borealopelta markmitchelli: The Living Tank Just Wasn’t Enough

Article by: Adam Manning
Edited by: J. D. Dixon

The incredible fossil, which took over 7, 000 hours to prepare. Available at: https://www.nationalgeographic.com/magazine/2017/06/dinosaur-nodosaur-fossil-discovery/.

One unlucky day, around 111 million years (Ma) ago, a large, lumbering dinosaur wandered the area that in future would become Alberta, Canada. Suddenly it was swept into a river, possibly by a flood, and its body washed out to sea, where it eventually sank. When it hit the seabed, sediment was thrown upwards and gently buried the body. Over millions of years, more sediment accumulated over the dinosaur, fossilising it with life-like precision. Then, on the 21st of March 2011, a heavy equipment operator named Shawn Funk uncovered the mummified dinosaur whilst working at Suncor Millenium Mine. 

This amazing fossil is the armoured Borealopelta markmitchelli, belonging to the Nodosauridae family of dinosaurs. Nodosaurs are a group closely related to the more famous Ankylosaurs, but the two clades diverged from each other in the Middle Jurassic. The name ‘Borealopelta appropriately means ‘Northern Shield’, while ‘markmitchelli’ honours Mark Mitchell, who spent more than 7,000 hours preparing this spectacular specimen. This animal was a sizeable herbivore, estimated to have weighed around 1300 kg and be approximately 5.5 m in length. 

If you are interested in examining this amazing fossil for yourself, follow this link to see a virtual 3D model: https://www.nationalgeographic.com/magazine/2017/06/nodosaur-3d-interactive-dinosaur-fossil/.

An illustration of the complete fossil in dorsal view, showing preservation of the different tissue types (A). Accompanying this are two drawings of the skull in dorsal (B) and lateral (C) views. Figure taken from Brown, et al, 2017. Available at: https://www.sciencedirect.com/science/article/pii/S0960982217308084.

Finds like this, where the animal has been completely ‘mummified’, are extremely rare and valuable. This is because they can give precise information on the animal’s morphology, like the positions of the animal’s osteoderms in life. From this fossil, we know that Borealopelta markmitchelli had osteoderms forming body armour similar to that seen in modern crocodiles, with bony spines extending outwards along its length. These spines may have been used in sociosexual display, as well as to deter predators. 

Even more incredibly, palaeontologists have even been able to work out the colour of this armoured beast. 

(Click here for our article on Sinosauropteryx to find out more about fossilised colours).

Unlike in Sinosauropteryx, the melanosomes had not been preserved, but chemical analysis of this fossil showed that Borealopelta markmitchelli was likely a reddish-brown pigment. This can be worked out because of the pheomelanin-rich melanin, which traces can still be picked up. These melanosomes are also more unstable than other melanosomes under heat and pressure, so explains why they weren’t preserved. Moreover, Borealopelta markmitchelli exhibits countershading, with a much lighter underside, just like with Sinosauropteryx.

A reconstruction of Borealopelta in life. Available at: https://www.inverse.com/article/35033-alberta-nodosaur-dinosaur-color-royal-tyrrell.

The presence of the countershading reveals a lot about the world this dinosaur lived in. The main function of countershading in modern animals is thought to be for camouflage. Many small animals at high risk of predation display this kind of colouration today, but it is much less common in larger animals. Animals like rhinos and elephants have no need for this kind of camouflage because their sheer size keeps them safe from most predators. This means that Borealopelta markmitchelli, despite its huge size by modern mammalian standards, was still at risk from predation by the large non-avian theropod carnivores, such as Acrocanthosaurus, that shared its home. These predators were likely very visual hunters, so Borealopelta markmitchelli used its countershading to help camouflage itself from their gaze.

In sum, this amazing specimen not only shows the morphology of this beautiful animal, but gives a rare insight into the extreme predator-prey dynamics of the Early Cretaceous period, and the arms race between predator and prey that resulted in such amazing adaptations in both parties. The specimen itself can now be found in the Royal Tyrrell Museum.

Image References
[1] The incredible fossil, which took over 7, 000 hours to prepare. Available at: https://www.nationalgeographic.com/magazine/2017/06/dinosaur-nodosaur-fossil-discovery/.
[2] An illustration of the complete fossil in dorsal view, showing preservation of the different tissue types (A). Accompanying this are two drawings of the skull in dorsal (B) and lateral (C) views. Figure taken from Brown, et al, 2017. Available at: https://www.sciencedirect.com/science/article/pii/S0960982217308084.
[3] A reconstruction of Borealopelta in life. Available at: https://www.inverse.com/article/35033-alberta-nodosaur-dinosaur-color-royal-tyrrell.

Information References and Further Sources
[1] Brown, C. M., Henderson, D. M., Vinther, J., Fletcher, I., Sistiage, A., Herrera, J., and Summons, R. E. (2017). ‘An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics’, Current Biology, 27 (16), pp. 2514-2521.e3. DOI: https://doi.org/10.1016/j.cub.2017.06.071. Accessed 14th October 2019. Click Here.
[2] Daley, J. (2017). ‘Spectacularly Detailed Armored Dinosaur “Mummy” Makes Its Debut’, Smithsonian Magazine. Accessed 14th October 2019. Click Here.
[3] Galván, I., and Solano, F. (2016). ‘Bird Integumentary Melanins: Biosynthesis, Forms, Function and Evolution’, International Journal of Molecular Sciences, 17(4), pp. 520. DOI: https://doi.org/10.3390/ijms17040520. Accessed 14th October 2019. Click Here.
[4] Greshko, M. (2017). ‘The Amazing Dinosaur Found (Accidentally) by Miners in Canada’, National Geographic. Accessed 14th October 2019. Click Here.