Unusual lesions and puncture marks found on tyrannosaurid skulls have had a major impact on our understanding of the lives of the tyrannosaurs, as detailed by two recent studies coming out of the US. In a paper published in this month’s Palaios, a team from the Northern Illinois University and the Burpee Museum of Natural History in Rockford have focussed their attention on “Jane,” a 7-metre-long Tyrannosaurus Rex skeleton with a slightly asymmetrical snout and four partially-healed oblong lesions along the left side of its skull. Discovered in 2001 in the Hell Creek Formation, Montana, Jane could be evidence of intraspecific aggression amongst juvenile tyrannosaurs, most likely competing for dominance, territory, or perhaps resources.
How the team came to this assumption was by comparing the positioning and orientation of the lesions along Jane’s nasal and maxilla regions to the jaw shape of the only fossil vertebrates found in the Hell Creek Formation that would have been large enough to inflict such wounds – theropods and crocodilians. They found that the size, shape, and spacing of juvenile theropod teeth corresponded convincingly to the positioning of Jane’s lesions, unlike those of a crocodilian jaw (see pic below). Evidence of face-biting is not uncommon in the tyrannosaurid fossil record, but this is the first indication that this kind of behaviour was not just restricted to fully-matured adults. As Jane’s age has been estimated at 12-years-old, two years prior to the age of sexual maturity for the Tyrannosaurus Rex, the possibility that this was strictly part of courtship-related behaviour has been ruled out.
Further, in their examination of Jane’s puncture marks, the team found indications of partial healing through bone repair, which suggests that this face-biting was not typically fatal, however could cause a slight warping of the muzzle as it remodelled itself. “Jane has what we call a boxer’s nose,” Joe Peterson, lead author of the study told Science Daily. “Her snout bends slightly to the left. It was probably broken and healed back crooked.”
But if all this talk of tyrannosaurid face sores leaves you with a distinct feeling of déjà vu, Peterson is careful to point out that Jane’s are a different type of lesion to those found on the famous 13-metre-long Tyrannosaurus Rex fossil, nicknamed “Sue,” which have recently been attributed to a parasitic infection (see pic above). “The parasite that has been described causes lesions on the lower jaw,” he notes. “With Jane, the lesions are on the actual face and are not the same type of structures we see on Sue.”
The other kind of face lesions which appear on many tyrannosaurid specimens, including Sue, indicates that the tyrannosaurs faced a far more serious threat than aggressive, face-biting peers. In a recent study published in PLoS One, Ewan Wolff from the University of Wisconsin describes a parasitic infection which causes severe erosion of the jaw bone and ulceration of the mouth and oesophagus, ultimately leading to death by starvation. Of the 61 tyrannosaurid specimens Wolff examined, 15% of them have the tell-tale signs of this infection – several smooth-edged pits in the lower jaw bone – as opposed to the more rough-edged bite marks found in Jane’s skull. However, in many of the specimens examined both kinds of lesions are present, suggesting that the infection could have been transmitted through intraspecific face-biting in much the same way as the cancer currently threatening to drive Tasmanian devils to extinction.
What Wolff also found is that the lesions in the jaw bones of these tyrannosaurid specimens are remarkably similar to those found in the beaks of modern birds such as turkeys, chickens and pigeons which have been infected by a protozoan called Trichomonas gallinae. These modern birds can pass trichomonosis on by simply touching each other on the beak, which can lead to a severe ulceration of the upper digestive system and then starvation. This shared affliction is yet further evidence of how closely related birds are to their dinosaur ancestors.
So all of this fighting and infection pretty much means the Tyrannosaurus Rex is the grossest dinosaur ever and woe betide anyone who invites one or more of them into their house to hang. Like one aftermoon Pteranodon would be over at Euhelopus’ house having Fruitloops and expensive dessert wine because Euhelopus’ parents are away for the weekend and Pteranodon is all like, “Dude. I cannot believe you didn’t tell me your parents were going away. What’s the fucking matter with you? We have got to have a party.”
And Euhelopus is like, “I guess I just forgot. Yeah, we could have a few people over. So long as they mind the carpet and shit.”
And with that Pteranodon goes a bit nuts and invites half the year (the cool half) to a party at Euhelopus’ place. Then they go to the bottle shop with Euhelopus’ little brother and their fake ID’s to pick up some Jager, (but Euhelopus’ little brother has to wait in the gift shop next door because he’s too little to have a fake ID) and Pteranodon’s all, “He doesn’t expect to come, does he?” expressing concern that he might spread his tweenaged uncoolness everywhere and make them look uncool by association. Euhelopus is like, “Well yeah, we can’t kick him out of the house, plus we have to keep him happy or he’ll call mum.”
“Fuck that. I’ve got an idea.”
So they sit Euhelopus‘ little brother down and Pteranodon’s all like, “So we’ve got a special job for you at the party. We need you to wait at the front door and make sure no one who isn’t on the list comes in. Sound good?”
“Cool. And just remember one thing – it’s very important that you don’t let the Tyrannosaurus Rex twins in.”
“Because they have gross skin problems and they’re always fighting. They’re fucked. If you have to choose between the Tyrannosaurus Rex twins and a homeless leper, we’d rather you choose the leper. But obviously don’t, because they’re fucked too.”
“Don’t swear in front of my brother.”
So a few hours into the party and Euhelopus has already gotten properly drunk and is slurring to the Diplodocus about assignments or something in the kitchen, while Pteranodon has disappeared altogether (although someone said they thought they saw him sneaking off to the park with some lady Pterodactyl under his wing). Suddenly Euhelopus’ little brother runs into the kitchen all panicky like, “Erm, promise you wont be mad…?”
And Euhelopus is all, “Ugh. Can’t speak. Not mad. I think I threw up in mum and dad’s shower.”
“In that case… I accidentally let the twins in and… Hey are those two girls making out? They need more alcohol. You’re not going to finish this, are you? Cool.”
Lucky for his little brother, Euhelopus is too drunk to care and/or comprehend, and manages to wander out onto the front lawn to pass out instead, but not before Pteranodon saunters over all like, “Dude.”
“Ugh… Hey where’s the girl?”
“She needed to pee, so I walked her to the bathroom, but then she passed out.”
“Nah it’s cool. She let me touch her boobs first.”
“Yeah. Erm, you know your brother let the Tyrannosaurus Rex twins in, right? Euhelopus? The twins…? Euhelopus..?”
Meanwhile the twins are stomping around the largely deserted living room with a bag of wine grasped in each little hand, taking generous gulps before spitting it out on the walls and carpet because it hurts too much to swallow. Then one of them is like, “Whoa, your face herpes looks fully gross in this light.”
And the other one responds, all like, “Bullshit, it’s not face herpes and you know it. Plus yours is way worse anyway. Which is just as well because it takes the focus away from your ugly.”
“Ha. I’ll show you ugly!” And with that an all-out face-biting brawl errupts, their tails swinging violently into Euhelopus‘ mum’s vases, the Diplodocus’ bottle of Jack, and Euhelopus‘ little brother’s fish tank, sweeping them all onto the floor in a sharp, soggy, and occasionally twitching mess that would likely result in an enormous stained patch of carpet no one could walk on in bare feet for months.
At that moment Euhelopus‘ parents return home early and start furiously kicking everyone out, just as Pteranodon is stumbling into the loungeroom with a lady Pterodactyl (a different one) under his wing all like, “I can’t believe you just showed me your… Shit.”
“Pteranodon, OH MY GOD, who let tyrannosaurs in our house, why is the carpet covered in wine and goldfish, and did someone give our budgie face herpes?!”
PLoS One (open access) // Palaios // Second illustration by Erica Lyn Schmidt.