Tyrannosaurs wrecks Triceratops

Well, this doesn't need a caption.

Predicting what will become a palaeoart meme is a dark, mysterious art. Sometimes news drops that should, given everything we know about the folks who create and like palaeoart, go absolutely viral. It should be illustrated again and again, find its way into books, magazines and maybe even documentaries, and inspire so much online content that old, miserable people like myself become quietly bored and tired of seeing it. But not all news of this sort takes hold among artists and, for whatever reason, it falls through the cracks.

Enter, stage left, the decade-old proposal that consumption of Triceratops carcasses by Tyrannosaurus involved the literal decapitation of the horned dinosaur corpse. Holy cow, how did we miss that one? Initially pitched in a conference poster at the 2012 SVP meeting by Denver Fowler and colleagues, the “How to eat a Triceratops” hypothesis has made a decent splash outside of the palaeoart community. It was featured in Nature and New Scientist among many other news outlets back in 2012, and the then-active Walking with Dinosaurs website turned it into a short film. The Smithsonian mounted the Nation's T. rex specimen gripping a Triceratops frill, an action hypothesised by Fowler et al. as necessary to get at the neck steaks beneath. But even with widespread sharing of a Nate Carroll graphic operating as an instruction manual for palaeoartists (below), the internet has not been inundated with images of Tyrannosaurus ripping the heads of horned dinosaurs, aside from rare examples like Luis Rey's take. I can't be the only one finding this strange, especially given the amount of T. rex art out there. Come on, people: it’s T. rex pulling the head off Triceratops! Were we asleep in 2012? As you've already worked out, the image above is my atonement for missing such an awesome source of palaeoartistic inspiration.

Nate Carroll's guide to eating Triceratops necks, if you're a T. rex. A, grab frill; B, use the frill as a lever to tear the neck; C, pull the head off; D, eat. It's not quite as straightforward as ordering a pizza, but you can't argue with the results. (From SciTechDaily)

Of course, and as Denver has noted on his website in response to the press interest in this hypothesis, we need to tread carefully around the “How to eat a Triceratops” data because it hasn’t been peer-reviewed and published yet. A paper is on the way but, for now, what’s suggested in the abstract is exciting and compelling. A collection of c. 100 Triceratops was examined for bite marks to reveal a large number (maybe as high as c. 18%) with scores and punctures attributable to T. rex teeth. It’s rare to allocate theropod bites to a single species but, among the very latest Cretaceous deposits in western North America, Tyrannosaurus is the only animal that was capable of leaving gigantic punctures and gouges in dinosaur bones. And if that's not convincing enough, casts of tooth marks sometimes replicate T. rex dental morphologies with precision (Erickson and Olsen 1996). Using these criteria, dozens of hadrosaur and horned dinosaur specimens with bites from Tyrannosaurus, as well as some T. rex bones with cannibalistic feeding traces, have been identified in recent decades (e.g. Horner and Lessem 1993; Erickson and Olsen 1996; Carpenter 1998; Happ 2008; Longrich et al. 2010; Depalma et al. 2013; Mclain et al. 2018). This work is all so recent because historic collection and examination practises tended to overlook T. rex feeding traces, so we're only now learning how common — relatively speaking — these marks are.

Tyrannosaurus tooth marks on horned dinosaur frills have been reported outside of the Fowler et al. study, suggesting whatever behaviour these traces represent may have been widespread and routine. These examples are from Longrich et al. (2010): C is only tentatively identified as a ceratopsid frill element, but D is confidently identified as a right squmosal (i.e. the bone forming the right lateral frill region).

What specifically underpins the “How to eat Triceratops” hypothesis are bite marks in specific places on the back of Triceratops skulls. Specifically, multiple specimens show tooth gouges and punctures on Triceratops frills, and these are difficult to explain as actual feeding traces. So far as we can tell, there wasn’t much to eat on this part of the Triceratops body. Perhaps, instead, they represent carcass manipulation marks, where the head was adjusted and pulled about to move the corpse into a more accessible position? But there's more: Fowler et al. (2012) also report tooth traces on Triceratops occipital regions: parts of the skull situated deep within Triceratops neck tissues that would only be accessible on heads separated from their necks. It’s not much of a jump to link these traces: maybe all that jostling with the frills wasn't really about moving the whole carcass, but specifically to get at the neck soft-tissues? While the frill was probably an obstruction to biting the voluminous cervical musculature on a living Triceratops, in death it may have been a useful lever with which to manipulate and pull at the head. Given enough pulling, twisting and brute force, that mighty Triceratops head would eventually tear off: dinner is served, as they say. 

Indirectly supporting this idea is good evidence that T. rex feeding could be very destructive in general, even when consuming animals as large as Triceratops. One of the most famous specimens to record Tyrannosaurus bite marks is a Triceratops pelvis described by Greg Erickson and Kenneth Olsen in 1996. Riddled with up to 80 tooth marks across several surfaces, this gigantic limb girdle was clearly moved around a lot by the feeding Tyrannosaurus (or tyrannosauruses) and chunks were literally shorn off by powerful bites, including one of the iliac blades and (almost) half a vertebra. The latter only remained attached by a small amount of bone and Erickson and Olsen ascribed this to the act of separating the pelvis from the rest of the body: a tremendous feat if it happened. Given this specimen, and the wealth of other fossils demonstrating the strength and force of a feeding Tyrannosaurus, I can totally buy that T. rex could decapitate Triceratops carcasses to access a bounty of horned dinosaur neck meat.

A caveat to all this, and a particularly necessary one in case we get swept along by the T. rex hype train, is that we shouldn’t imagine major dismantling of Triceratops carcasses taking place with freshly killed or otherwise untouched bodies. Neat as it is to imagine Tyrannosaurus ripping the head from a freshly-vanquished Triceratops, waving it aloft and roaring triumphantly like some kind of 8-tonne Predator, modern animals generally follow reliable carcass consumption patterns where easily accessed and nutritious tissues are eaten before difficult-to-access or less-nutritional parts (Blumenschine 1986). Typically, animal hindquarters are eaten first, then the contents of the abdominal cavity, followed by the forequarters and any fleshy bits on the skull, then the limb bones, and finally the internal contents of the head. Under this model, we might place Triceratops neck tissues as “mid-priority” fodder: decent enough eating to make them desirable, but only worth the energy and time investment of bypassing the head if more sought-after parts of a carcass are gone. I’ve attempted to show this in my artwork above by depicting the legs and arms of the Triceratops as already consumed, and the ribs are already exposed from the body being opened to eat the internal organs.

The image at the top of this post isn't my first dance with the Triceratops decapitation hypothesis. In this painting from earlier this year, the decapitated Javelina Formation ceratopsid is meant to be the result of tyrannosaur activity that preceded the arrival of more noble, elegant creatures who'll clear up the mess.

And that's where I'll leave things today. As noted above, a paper on all this is in the works and I'm looking forward to reading it when it comes out. I'm resisting the temptation to springboard onto other topics related to T. rex tooth marks: feeding habits, neck and jaw strength, and their embarrassment of older considerations of Tyrannosaurus tooth and jaw strength (“...its viscous-looking teeth were not as bad as they seemed: if it had tried to tackle living animals, the teeth would have snapped off in the struggle” - oh, Halstead 1975. that comment has not aged well). But time isn’t on my side and we’ll have to save that for another time. Or maybe we’ll finally move away from posts about big theropods. There is a good reason for all this, honest.

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References

• Blumenschine, R. J. (1986). Carcass consumption sequences and the archaeological distinction of scavenging and hunting. journal of Human Evolution, 15(8), 639-659.
• Carpenter, K. (1998). Evidence of predatory behavior by carnivorous dinosaurs. Gaia, 15, 135-144.
• DePalma, R. A., Burnham, D. A., Martin, L. D., Rothschild, B. M., & Larson, P. L. (2013). Physical evidence of predatory behavior in Tyrannosaurus rex. Proceedings of the National Academy of Sciences, 110(31), 12560-12564.
• Erickson, G. M., & Olson, K. H. (1996). Bite marks attributable to Tyrannosaurus rex: preliminary description and implications. Journal of Vertebrate Paleontology, 16(1), 175-178.
• Fowler, D.W., Scannella, J.B., Goodwin, M.G., & Horner, J.R. (2012) How to eat a Triceratops: large sample of toothmarks provides new insight into the feeding behavior of Tyrannosaurus. Journal of Vertebrate Paleontology 32(5, abstracts vol): 96
• Halstead, L. B. (1975). The evolution and ecology of the dinosaurs. P. Lowe.
• Happ, J. (2008). An analysis of predator-prey behavior in a head-to-head encounter between Tyrannosaurus rex and Triceratops. In Larson P. & Carpenter, K. Tyrannosaurus rex the Tyrant king, Indiana University Press. p. 355-370.
• Horner, J. R., & Lessem, D. (1993). The complete T. rex. Simon & Schuster.
• Longrich, N. R., Horner, J. R., Erickson, G. M., & Currie, P. J. (2010). Cannibalism in Tyrannosaurus rex. PLoS One, 5(10), e13419.
• Mclain, M. A., Nelsen, D., Snyder, K., Griffin, C. T., Siviero, B., Brand, L. R., & Chadwick, A. V. (2018). Tyrannosaur cannibalism: a case of a tooth-traced tyrannosaurid bone in the Lance Formation (Maastrichtian), Wyoming. Palaios, 33(4), 164-173.