Tuesday, 15 October 2013

New Evidence Suggests That Some Dinosaurs May Have Been Venomous

Dilophosaurus as featured in Jurassic Park. Is
it possible that it may have been venomous?
When Jurassic Park hit the screens in 1993 it was a hit. Yet while it attracted a wide-ranging fan base, it also received wide criticisms due to its scientific inaccuracies.

The resurrection of dinosaurs from DNA contained in mosquitoes preserved in amber gained the most flak. Yet the portrayal of one particular dinosaur raised the hackles of palaeontologists worldwide. Having crashed a car into one of the dinosaur compounds, the villain Dennis Nedry, encountered a venom-spitting Dilophosaurus, which despite a rather sweet if unnerving disposition, ended up killing him.

Many species of reptile certainly possessed venom, but no evidence had been found to suggest that dinosaurs had the same capacity. Now a re-examination of fossils of a 125 million year old dinosaur Sinornithosaurus offers striking new evidence that some indeed may have indeed been venomous.

The grooves identified in the teeth of Sinornithosaurus
A team of palaeontologists, led by Enpu Gong from the Chinese Academy of Sciences, noted the presence of a groove running down the back teeth of a well preserved specimen of Sinornithosaurus.

Some snakes possess hollow front teeth which are used like hypodermic needles to inject venom into their prey. Others, referred to as rear-fanged snakes, use their back teeth. The venom is guided by a groove running along the tooth, similar in shape to the one identified by Gong in the teeth of Sinornithosaurus. He may have identified a pocket in the skull which housed the venom gland also.

'The ductwork leading out of the venom gland gave the venom a way to travel to the base of the teeth, where the venom welled up in the grooves,' said study co-author David Burnham from the University of Kansas Natural History Museum and Biodiversity Research Center. 'So when they sank their teeth into tissue of the victim, it allowed the venom, which was really enhanced saliva, to get into the wound.' Exactly how the venom, if that is what the grooves are indicative of, may have acted is another matter.

In some predators it is the killing blow, in others it assists the capture of prey. Based on the length of the fangs of Sinornithosaurus which made them susceptible to damage and the narrow snout, Gong has suggested that the venom was the primary means of attack. It used the long fangs to inject a fast-acting toxin through layers of feathers or thick skin, features common in reptiles in the environment in which it lived.

A diagram indicating the structures identified by Gong
in the 125 million year old skull of Sinornithosaurus
Grooved teeth are rarely found in non-venomous organisms which gives credence to his theory. It is possible that the grooves were created by damage to the specimen during the fossilisation process. Palaeontologists have noted that other species of predatory dinosaur also have grooved teeth and believe that this prevented them from becoming stuck in their prey.

While Gong's evidence is not conclusive, it is a good start. More evidence is needed, in particular soft body parts such as glands or ducts, before we can say for certain that some dinosaurs were venomous. Personally I am hopeful. Sinornithosaurus specimens often come from localities renowned for their degree of fidelity. If dinosaurs were venomous then I am sure that some definite anatomical record will be found. In time we may even be able to say that Dilophosaurus itself had venom and that Jurassic Park is nearer to fact than fantasy.