Early dinosaurs weren't just covered in feathers. They were also poisonous.

Analysis of skulls belonging to different species of Sinornithosaurus, a group of feathered predatory theropods that lived 125 million years ago in what is now northeast China, shows skeletal features reminiscent of modern rear-fanged snakes and lizards.

Sinornithosaurus' rear teeth were long, with grooves connected to ducts running under their fangs to a pocket that could have housed a venom gland. "These features are all analogous to the venomous morphology of lizards," wrote paleontologists in a paper published Monday in the Proceedings of the National Academy of Sciences.

The researchers speculate that Sinornithosaurus' long teeth could have penetrated the feathers of its avian prey, penetrating just far enough to release their poison. Like most modern rear-fanged reptiles, the venom probably wasn't lethal, but instead shocked prey into immobility.

Short front teeth were probably used "to pluck the feathers off their victims," wrote the researchers, who suggest that other members of Sinornithosaurus' family, including the velociraptors of Jurassic Park fame, had the same venomous capabilities.

Images: 1. Sinornithosaurus skull at left and illustration at right/PNAS

2. A rear-fanged hognose snake scull/WikiMedia

See Also:

*Citation: "The birdlike raptor Sinornithosaurus was venomous." By Enpu Gonga, Larry D. Martin, David A. Burnham, and Amanda R. Falk. Proceedings of the National Academy of Sciences, Vol. 106 No. 51, December 22, 2009. *

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecosystem and planetary tipping points.