One of the most read posts on the Musings is that on my paper on theropod predatory ecology in which Oli Rauhut and I suggest that most big theropod predators probably targeted juvenile dinosaurs rather than adults. We covered a bunch of lines of evidence but one of those was the oft under reported area of dinosaur feeding traces. Quite literally bite marks left on bones by theropods.
There seem to be quite a few of these around according to some surveys, but they don’t get much attention. There’s a small (but growing) list of papers that describe individual bites or small sets of bites in some detail, and there’s a couple of review papers that talk about very large numbers of bites with little detail and not much in between. Thus while there are therefore at least several hundred documented bite marks, and probably quite a few more, only a dozen or so are actually described and illustrated in the literature. That makes it pretty hard to say much about them, since we don’t know what the distribution is like in terms of sizes, numbers, or any other obvious patterns.
I can see why this might often get overlooked, bites aren’t always obvious and nor can they always be easily distinguished from other forms of damage (though quite a few are very obvious). The obvious reason though, for not taking the time out to describe these, is that there is often only very little to say. It’s not at all clear, or even possible to tell most of the time, if the marks were made by an animal just biting another, that actually killed the other, or was merely scavenging a carcass. It’s not always even obvious which animal was bitten (if the marks are on an isolated bone) and it’s very hard to narrow down what the biting animal may have been too. Package all of this together and tooth marks are sadly, if understandably, relegated to being a ‘novelty’ rather than necessarily having anything interesting to say about predatory behaviour or trophic relationships.
However exceptions do exist, like the macerated Triceratops pelvis that’s full of deep T. rex tooth shaped holes, or the pterosaur bone with a dromaeosaur tooth wedged into it surrounded by score marks as the teeth scraped across the bones. These two examples actually demonstrate the two stereotypical bite marks with others usually falling somewhere between the two (obviously this means a dingle trace, there can be multiple kinds present on a bone or skeleton that has suffered bites). Either one will see deep punctures (or even ‘bite-through’ of the whole bone) that are tooth shaped – that is the tooth has penetrated the bone, or there will be scrape marks where the tooth has hit the bone surface and then been drawn across it. The latter is more common since few theropods probably had the power, or even desire to try and crack through big bones and of course we suggest that they probably weren’t even encountering them that often in any case.
Still, for all the problems that are associated with trying to pick out the details of feeding traces they can, on occasion, offer some illumination on the living habits of various dinosaurs. Like the example I’ll cover tomorrow with this shameless cliffhanger and obvious plug…