Monday, December 21, 2009

Venomous Dinosaurs


Above: Illustration of a Sinornithosaurus skull.

A few of you may remember a little 1993 picture called Jurassic Park. In the film as in the novel it was based on, a point was made of showing how unpredictable cloning extinct organisms could be, and that we would not be able to anticipate all the dangers dinosaurs posed just from their fossil remains. To illustrate this, author Michael Crichton invented the idea that the basal theropod Dilophosaurus was venomous. This was, of course, completely fictional and only present to make a philosophical point. There is no evidence whatsoever that this dino had venom, let alone could spit it like a cobra, let alone had a ridiculous display like a rattling frill-neck lizard (added only for the movie).

However, while Dilophosaurus in particular was probably not venomous (and if it was, the late Crichton should be hailed as a prophet for picking that specific dino out of his... orifice), this doesn't rule out the possibility that some dinosaurs were. Poison or venom of come kind exists in a wide selection of modern vertebrates, from amphibians, to lizards (like the gila monster and Komodo dragon) and even birds such as the Hooded Pitohui, which is very aptly named, as the neurotoxins in its feathers cause predators to promptly spit it out.

There has in the past been some goss to the effect that we have evidence for venomous dinosaurs (the difference between venom and poison: poison is ingested or absorbed from prey to predator, venom is injected from predator into prey). A 2 cm long tooth with a longitudinal groove, reported from Mexico in 2001, was suggested to come from a venomous theropod.

Those grooves, which are actually present in most theropod teeth to some extent, are the issue of a new controversy over a paper on the Chinese dromaeosaurid Sinornithosaurus, which we've covered before regarding it's hind wings, or lack therof. A new study looks at the unusually positioned gooves on sinornithosaur teeth, and speculates that these could have delivered venom. The researchers even identify an opening in the upper jaw bone where the venom gland may have been. (left: Sinornithosaurus by FunkMonk. Licensed.)

This is exciting stuff, but take it with a grain of salt. Ed Young does a good job covering the situation at his blog. Basically, it's entirely possible that the grooves are simply features typical of other theropods. Many animals have grooves on their teeth to negate any suction that would occur when pulling the tooth out of flesh. However, Young also reports that Bryan Fry, who discovered the venom of Komodo dragons, has stated that grooved never occur on the posterior side of the tooth surface except in venomous animals, which sounds pretty convincing.

The authors of the new paper cite the length of the grooved teeth as evidence that they were "fangs", but it really just looks like they're out of socket, the way many theropod skulls are mounted in museums. T. rex famously have 6-inch teeth, but that includes the roots. Really, only 2 or three of those inches would protrude from the jaw. Fossils that have been crushed and distorted are also susceptible to out of socket teeth making the dentition look more formidable (and more fang-like) than it really was.

Above: T. rex mount with teeth dangling out of the mouth like it just finished a brutal hockey game. Photo by Quadell from Wikipedia. Licensed.

Obviously more investigation needs to be done, but famous TV personality Dr Tom Holtz is on record saying he evidence is weak, so let's not be too hasty with conclusions here.

You can read a news article about the find here.

8 comments:

  1. It would be really cool if they could find a venomous dinosaur. It would make them even more bizarre than we already know them to be. It's too bad the evidence is weak.

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  2. Thought-provoking theory, but not very conclusive.

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  3. Wasn't that the one that killed the fat man in Jurassic Park?

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  4. Clasamente: No, that was Dilophosaurus, which most certainly was not venomous in real life (nor did it have that large rattling frill). Both features were made up for the book/movie.

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  5. Thank You!!! I've been trying to tell people that for a while now! Instead, they ignorantly attack Dr. Crichton for his inaccuracy!

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  6. One thing I have to inject- on another site, they compared the grooves in the teeth to the grooves (fullers) on some types of swords. They then said these grooves were to allow blood to drain- which is wrong, the fuller on a sword is not a 'blood groove', it's designed to lighten the blade without reducing its strength.

    As a guy who makes swords as a hobby, I hate seeing them referred to as 'blood grooves'.

    Anyways, it seems unlikely to me, but could these grooves have had a similar function to the fullers found in swords?

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  7. Well, the sword analogy could be valid in taxa that have such grooves (I've seen this proposed foe some primates with grooved teeth). However, it doesn't get around the main flaw of the paper, that the *roots* of the teeth, not the crowns, are grooved, and unless the tooth was loose or falling out, they wouldn't protrude above the gum line. The teeth in the fossil are clearly disarticulated.

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  8. Since i was a kid i was very passionate about science and dinosaurs. The way how this animal species have disappeared over night is just fascinating.

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