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Top 10 Open Access Fossil Taxa of 2017: Daspletosaurus horneri

Tyrannosaurs – the weird lovers we always wanted them to be?

Coming in at a tied 6/7th place for the Top 10 Open Access Fossil Taxa of 2017 is a dinosaur that needs no introduction.

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Crocodiles are some of the most efficient, archaic, god-like killing machines alive on this planet. One of the things that makes them so incredibly good at inducing death is a whole toolkit of lethal hunting weapons. Besides dagger teeth, the ninja-quality death roll, and a sneak level only otherwise obtainable through serious grinding in Skyrim, crocodiles have a 6th sense*.

Now, imagine if a tyrannosaur had that same sensory system.

Researchers, led by Thomas Carr of Carthage College, Wisconsin (TyrannosaurCarr to his online friends), recently discovered a new species of tyrannosaur that had a bit of a crocodilian face-lift.

Jurassic World, you got it all wrong. Why make up a new dinosaur by fusing genetics from random animals, when you already have one that was freakishly terrifying enough? And also real.

Daspletosaurus horneri was an apex predator of its time, and part of a direct ancestor-descendant relationship with its generic cousin Daspletosaurus torosus, providing rare evidence of ‘anagenesis’ in the dinosaur fossil record. The new species is named after Jack Horner, a man who’s continued dedication to, and discovery of, dinosaurs helps to inspire a global love in Palaeontology.

The new species hails from the 75.1-74.4 million year old rocks (that’s precise, for geologists) of the Two Medicine Formation of Montana. This makes it just slightly older than T. rex, and went extinct before the king of beasts dispersed into North America from Asia.

Getting jiggy with it? Image: Kevin Guertin, CC BY-SA 2.0 (source)

Never smile at a tyrannosaur

D. horneri had unusual coarsely textured snout bones, similar to what we see in the pitted skulls of modern crocodiles and alligators. The researchers think this is evidence that the tyrannocroc had scaly skin with a high-resolution tactile sensitivity. The jaw bones were resplendent with dozens of tiny holes, called neurovascular foramina, just like we see in birds, crocodiles and their ancestors. These foramina usually indicate where a nerve would have ended for some specific sensory purpose, such as detecting the movement of prey, and were more sensitive than human fingertips! You can bet if the US military were around 75 million years ago, they’d have been trying to develop this into some sort of crude battle armour (kevlarchosaur suit, anyone?).

Crocodiles, and sharks actually, are highly sensitive to the slightest twitch from a potential prey item. Mentally, it’s probably how Neo saw Agent Smith in the Matrix Revolutions just after he’d been blinded – imagine hunting in murky lake waters and this usefulness should become apparent. Such advanced sensory gear is also found in modern snakes, frogs (those vicious predators…), moles, and ducks.

How Daspletosaurus sensed other animals? (source)

But wait, tyrannosaurs aren’t crocodiles! And certainly (probably) didn’t spend most of their time hunting in water as semi-aquatic ambush predators. So why did D. horneri have such a sensitive snoot? Why indeed…

I sense dead dinosaurs

There are many possible suggestions here – one of the beautiful things about Palaeontology is that it allows you to explore your imagination (within scientific reasoning). It’s possible that the ‘tyrant lizards’ were gentle parents, carefully picking up their eggs and young, first hypothesised by Sarah Harding in The Lost World (she failed to confirm that hypothesis, much to one of her co-authors’ demise). Their snouts might have even useful as parental thermometers, able to detect changes in nest temperature.

Tyrannosaurs might have even been intimate playmates, rubbing each other’ faces with toothy caresses as a sign of affection. Tyrannosaur foreplay, folks. Modern examples of this include that couple you hate on the bus, and constantly scowl at muttering ‘Tcch, kids…” while secretly longing for your own youth/inner tyrannosaur to emerge. Of course, we’ll never know if this is what they were actually used for unless we catch an amorous couple in flagrante in the fossil record. We shall wait expectantly.

Reconstruction of Daspletosaurus’ facial coverings (Illustration © Dino Pulerà. All rights reserved)

Another possibility is that they were a bit more bitey, and enjoyed taking chunks out of each other’s faces during territorial battles, mating rituals, or because one forgot to pay their tab. There is some evidence showing that tyrannosaurs bit each other on the faces, for whatever reason, and lends a more violent interpretation to these sensory structures. Just like crocodylians, D. horneri had rough, bony protection around these nerves, that help to safeguard them during combat or hunting, providing good evidence for this sort of adaptation.

More than just a roar

We might never know what tyrannosaurs were really like in real life, until we invent time travel anyway (what’s taking physicists so long). This means that we have to be a little cautious in our interpretations of extinct animals, as often these are based on comparisons with modern analogues. Nonetheless, these clues do give us tantalising little insights into their behaviour, and indicate something altogether different from the stereotypical roaring tear-your-face off rampaging death-goose that still captivates our hearts and minds, and have inspired countless individuals to learn more about these wonderful creatures.

One thing remains for sure though. Daspletosaurus was not just a tyrannosaur with a face that only a mother could sense. It was whatever you imagine it to have been.

*Well, we assume it’s a 6th sense because they have the usual 5, but you never know.

Reference

Carr, T. D., Varricchio, D. J., Sedlmayr, J. C., Roberts, E. M., & Moore, J. R. (2017). A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports7, doi: 10.1038/srep44942

Featured Image: Luis Rey

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