A bird-like dinosaur used venom to kill its prey, paleontologists say.

Larry Martin and David Burnham of the University of Kansas in Lawrence were examining the fossil of Sinornithosaurus one day when they noticed a depression in the maxilla and a groove that led into the razor-sharp teeth. “We just looked at each other that day,” Martin told the Wichita Eagle. "And I said, ‘David, you do realize what this means?’ We knew at that moment, ‘Oh my gosh, this was a venomous animal.’”

The fossil, described in the early edition of Proceedings of the National Academy of Sciences, marks the first discovery of a potentially venomous dinosaur. Sinornithosaurus was about the size of turkey and had feathers on both its front and back legs. It likely fed on small birds in the forests of Cretaceous-era China, 128 million years ago. The fangs would only be able to penetrate 4 to 6 millimeters into the skin, allowing the poison to enter the bloodstream.

The venom would not necessarily kill the prey, but as in modern day Gila monsters and some rear-fanged snakes, it would induce “a state of shock.” (National Geographic)

“You wouldn’t have seen it coming,” Burnham told The Guardian. “It would have swooped down behind you from a low-hanging tree branch and attacked.”

Of course, not everyone is sold on the story. Brian Switek of the Dinosaur Tracking blog at Smithsonian.com writes, “The new study, while interesting, does not include compelling evidence that Sinornithosaurus or any other dinosaur was venomous.”

Image: David A. Burnham, University of Kansas Biodiversity Institute