Venomous Dinosaurs?

Anyone who has ever watched Jurassic Park will remember the iconic scenes with the venom-spitting Dilophosaurus. Its vibrant frill and the foul, sticky poison it spits to blind its prey made for dramatic imagery, but is any of grounded in reality? Were there any venomous dinosaurs?

As most dinosaur fans probably already know the film-makers of Jurassic Park were taking serious liberties with their depiction of DilophosaurusThe idea though that there could have been dinosaurs capable of producing venom is not totally absurd. Today venom comes in many different forms and has evolved independently many times. From jellyfish to rattlesnakes there is at least one member of just about every animal group that has developed the ability, even mammals. So why not dinosaurs?

Sinornithosaurus from the Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA. Source Wikimedia Commons.

Sinornithosaurus was first discovered in 1999; a 2m long, feathered predator from the Early Cretaceous of China it initially seemed very similar to many of the other small, carnivorous dinosaurs of the period. It wasn’t until a decade later in fact, in 2009, that a paper was published discussing some potentially unusual aspects of the animal’s skull. The paper noted three particularly key features; the skull they examined had unusually long teeth in the back of the upper jaw which the researchers compared to those of the “rear-fanged” snakes, and these teeth were grooved like those of many venomous animals which deliver poison through their bite. Finally Sinornithosaurus also had a space in the skull just above these teeth which is not seen in related species. The researchers interpreted this as the location of a possible venom gland, which would then supply the abnormally long, grooved teeth that would inject the venom into their prey. Taken altogether the researchers suggested this was excellent evidence that Sinornithosaurus was the first venomous dinosaur to ever be discovered.

Of course extraordinary claims require extraordinary evidence and the evidence in the case of Sinornithosaurus, while intriguing, was not exactly air-tight. In 2010 a paper making the counter-argument that Sinornithosaurus was not actually venomous was published. The paper disputed the original paper’s three key arguments. They pointed out that grooved teeth are not unusual either amongst predatory dinosaurs, or even amongst non-venomous animals in general. There are many species of primate for example that have grooves in their canine teeth that have no connection to venom delivery. The teeth themselves had moved out of their original position in the skull after death, making them appear abnormally long, and the researchers were also unable to identify the alleged space in the skull associated with a venom gland. They concluded there was no good evidence that Sinornithosaurus really was venomous.

Following this, also in 2010, the original researchers published a counter-counter argument reiterating their original conclusion that Sinornithosaurus really was venomous after all. They acknowledged that the teeth were slightly out of position but argued they were still unusually long compared to other, related species. They also argue that although grooved teeth are common in the dinosaur fossil record this could be because the ancestors of all these dinosaurs were also venomous and that non-venomous dinosaurs secondarily lost this ability while some, like Sinornithosaurus retained it. This is obviously a controversial idea and has not been widely accepted in the palaeontological community.

And that, for now, is that. So where does that leave us now? The evidence that Sinornithosaurus was actually venomous is still very thin and as far as I could find there have been no other suggestions of venomous dinosaurs being found in the fossil record. Is there any reason to think there might not have been any? In the absence of fossil evidence palaeontologists sometimes look at the behaviour of closely related animals to at least get a feeling of what is likely. And in this case the comparisons are compelling. Of course there are lots of venomous reptiles although the trait is mostly limited to the snakes and their relatives, which are not really close relatives of the dinosaurs. In fact the closest living animals to these dinosaurs are the birds and there is currently no known venomous species of bird. It’s not proof by any stretch but it is definitely suggestive.

Given the sheer range of diversity amongst the dinosaurs I wouldn’t be shocked if we did one day find unambiguous proof of venomous dinosaurs, but unfortunately I don’t think Sinornithosaurus is it.


Gong, E., L.D. Martin, D.E. Burnham, and A.R. Falk. (2009). “The birdlike raptor Sinornithosaurus was venomous.” Proceedings of the National Academy of Sciences,

Gianechini, F.A.; Agnolín, F.L.; Ezcurra, M.D. (2010). “A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus“. Paläontologische Zeitschrift85: 103–107. 

Gong, E.; Martin, L.D.; Burnham, D.A.; Falk, A.R. (2010).Evidence for a venomous Sinornithosaurus“. Paläontologische Zeitschrift. 85: 109–111. 

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