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.