Tonight I had the pleasure of attending an evening of Dinosaur discussion at the Ritzy bar in Brixton. Any presentation given indoors, without air conditioning, in the kind of heat capable of dispatching the slide projector, is going to thin out fast unless the subject material is really engaging. Suffice to say it was standing room only by the time Dr. Hone started.
Not afraid of tackling the contentious issues, he leapt right into the T rex: scavenger or predator debate. His stance, unsurprisingly, is that tyrannosaurs were like all other carnivorous animals: opportunistically killing what they could and scavenging what they couldn’t. He backed this up with examples of both from the fossil record.
Firstly, a Saurolophus so well preserved that there are impressions of its belly skin stretched over well articulated bones. The bones are immaculate… Except for the upper arm, which exhibits hundreds of delicately gnawed tyrannosaur tooth marks. The specimen is in river sediment, there are signs of debris from the river built up around the carcass. The implication is that Tarbosaurus
hunts using clods of earth as a weapon, like some giant, predatory dung beetle did not kill this animal. Instead, the tyrannosaur found a limb above ground that may or may not have belonged to a living animal still, and he fed on it – stripping the meat from the bones. Given the option, he probably would have preferred the thigh or the base of the tail, where there’s plenty of flesh. He did not have that luxury. There are other specimens which show bone punctures in places you couldn’t reach with all the flesh in place, which hint at scavenging, but none show quite so conclusively that the “6-ton roadrunner from hell” didn’t deliver the killing bite.
This time Dr Hone showed us a couple of Hadrosaur specimens which had been bitten and lived to tell the tale. Signs of bone growth around tyrannosaur tooth impressions in the prey animals are a nice indicator that Tyrannosaurus at least attempted to kill things. The fact that the specimens in question were both juveniles was very revealing also: if you add that to the coprolite containing ossified juvenile hadrosaur bones, you get an over-all impression that tyrannosaurs were just like every other predatory animal the world over – feeding on the young, the old, and the infirm rather than tackle the healthy adults.
Juveniles generally are absent from the fossil record, suggesting that many never made it to a place where they could fossilise gracefully – instead being picked off by carnivores. Where juveniles are known, their growth rates indicate that they grew fast. Just like a modern bird that grows poor quality feathers & matures in size rapidly – It just wasn’t safe to be small!
Dr David Hone has a blog over on Archosaur Musings, I’d encourage you to check it out. His talk inspired me to take up my pencils tonight. Watch this space…