Oh, oh, oh! This is an exciting one! Earlier this year, when the discovery that Komodo Dragons (Varanus komodoensis) are venomous was published, I idly wondered if any dinosaurs were as well. Komodo Dragons and dinosaurs are not closely related, so there was no reason to make that leap, beyond the fact that they are (or, in the case of dinosaurs, were) both large terrestrial reptiles, and that I want it to be true.
Well, it turns out I might yet be onto a winner with that one. A recent publication by Enpu Gong of the Chinese Academy of Sciences documents fossil evidence that Sinornithosaurus, a small Cretaceous theropod from what is now China, possessed a venomous bite. The venom gland itself, being soft tissue, has not been preserved1, but the skull contains a cavity that Gong believes could have contained one. More convincingly, the animal had long, grooved upper teeth, like those used by extant rear-fanged snakes to inject venom into prey, with voids above them, which could have functioned as local reservoirs.
Not everybody’s convinced, and I’d categorise the evidence as ‘strongly suggestive’ rather than a slam-dunk, but it’s fascinating stuff and lends a big pile of credibility to an idea that I really want to be true.
Check out Ed Young’s longer and better coverage, over at Not Exactly Rocket Science.
- Which is not to say that soft tissue can never leave fossil evidence, in fact Sinornithosaurus is also famous for being one of the first dinosaurs to be discovered with fossilised feather-impressions, merely that it is significantly rarer. [↩]
Yes, you read that right; in the second new lizardly discovery I’ve read about this week — this time at the excellent Not Exactly Rocket Science — it turns out that not only are Komodo Dragons (Varanus komodoensis) 3m long carnivorous lizards with razor-sharp, serrated teeth that can run at 20km/h, but they’re also venomous. You know, in case all that other stuff wasn’t enough to give you nightmares.
It was thought for decades that Komodo Dragons relied on the virulent cocktail of bacteria present in their mouths to infect and weaken prey when they bit them, so that they could hunt them down over a few days and finish the job. It turns out that, while their mouths certainly are rancid, they have an even nastier weapon in their arsenal.
Brian Fry of the University of Melbourne, tipped-off by the discovery in 2005 that a close relative of the Dragon (Varanus varius, the Lace Monitor) has venom glands, took an MRI of the head of a Komodo Dragon and demonstrated conclusively that it too is venomous. The venom in question is complex, but seems mainly tailored to increase blood loss from the gaping wounds left my the Dragon’s razor-like teeth and characteristic ‘backward-jerk’ biting motion, causing massive blood loss in the victim, weakening them and often leading quickly to shock, and then to death. It’s worth noting that even where the blood-loss is not sufficient to kill the victim, going into shock within sight of a hungry 3m carnivore probably will be.
Komodo Dragons being the largest extant reptiles, and me being me, the first thing I thought of when I read about this was the possibility that some dinosaurs may also have evolved a venomous bite, and I was pleased to see that I’m not alone; there a discussion of the subject in the comments at Not Exactly Rocket Science. Unfortunately, they agree with me: the idea is a bit of a stretch (OK, a lot of one,) since Komodo Dragons aren’t closely related to dinosaurs, and there are no known venomous examples of the closest extant relatives of dinosaurs: the birds. What this does show, however, is that it’s quite possible for reptiles — even large ones — to be venomous without providing any skeletal or dental evidence of the fact. So our conclusion has to be that some dinosaurs may have been venomous, but that we have no good reason to believe that they were.