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The Sinornithosaurus upper jaw has what may have been a pocket for a venom gland, a venom duct, and grooved teeth to aid venom delivery.

The Sinornithosaurus upper jaw has what may have been a pocket for a venom gland, a venom duct, and grooved teeth to aid venom delivery.

Illustration courtesy of National Academy of Sciences

Brian Handwerk

National Geographic News

Published December 21, 2009

Jurassic Park was packed with pseudo-science, but one of its fictions may have accidentally anticipated a dinosaur discovery announced today—venomous raptors.

Though a far cry from the movie's venom-spitting Dilophosaurus, the 125-million-year-old Sinornithosaurus may have attacked like today's rear-fanged snakes, a new study suggests.

Rear-fanged snakes don't inject venom. Instead, the toxin flows down a telltale groove in a fang's surface and into the bite wound, inducing a state of shock.

In Sinornithosaurus fossils, researchers discovered an intriguing pocket, possibly for a venom gland, connected to the base of a fang by a long groove, which likely housed a venom duct, the study says. Sinornithosaurus fangs also feature snakelike grooves in their surfaces.

"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 paleontologist David Burnham of 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."

Dinosaur's Venom Stupified Prey?

Turkey-size Sinornithosaurus, which likely had feathers, lived in the forests of what's now northeastern China, and was a member of the family Dromaeosauridae, as was another Jurassic Park baddie, Velociraptor. Birdlike Sinornithosaurus probably used its longish fangs to put the bite on prehistoric birds, Burnham said.

Like rear-fanged snakes and some lizards, the dinosaur probably had nonfatal venom that could shock its victims into a defenseless stupor—allowing Sinornithosaurus to eat in peace.

Dragons, Dinosaurs, and Venom's Shadowy Past

Burnham's research was inspired by the 2000 find of another possibly venomous dinosaur fang and by a recent discovery that the today's top lizard predator, the Komodo dragon, has a venomous bite that weakens victims so they can be eaten later.

Though believed to have descended from dinosaurs like Sinornithosaurus, today's birds are toothless and so lack a venom delivery system (though some birds do have toxic skin and feathers).

But Burnham is more interested in where Sinornithosaurus' venom ability came from than how it evolved.

"How primitive is venom really? Does it go all the way back to the archosaurs?" he said, referring to reptiles thought to have predated dinosaurs by 30 million years or more. "These are things people haven't really tested yet."

Findings to be published tomorrow in the journal Proceedings of the National Academy of Sciences.

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