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Now the latest from the world of dinosaurs. If the thought of a razor-toothed dinosaur ripping into its prey is not scary enough, consider a venomous one. That's what some scientists are proposing after discovering an unusual fossil in China.

NPR's Christopher Joyce has that story.

CHRISTOPHER JOYCE: Sinornithosaurus was petite as dinosaurs go - think of a turkey with teeth. It ran with a tough crowd, though. It was cousin to the oh-so-scary velociraptor of "Jurassic Park" fame. Paleontologist David Burnham from the University of Kansas and a Chinese colleague were puzzled by a 125-million-year-old Sinornithosaurus in a museum, specifically, by its upper teeth.

Professor DAVID BURNHAM (Professor of Paleontology, University of Kansas): And we finally realized we're looking at the outside of these teeth and they're grooved. And we both look at each other and, you know, what? Why would an animal have grooved teeth?

JOYCE: It turns out some venomous snakes and lizards use grooved teeth to deliver poison. Burnham thinks this dinosaur did, too. Besides the teeth, another clue was a cavity in the jawbone where, he suggests, a venom gland could have been. He also found a channel leading from the cavity to ducts near some of the teeth. These teeth are about three inches long. Unlike the hypodermic-type teeth of a viper, they're farther back, where our premolars would be. That's much the same as rear-fanged snakes and lizards living now. Burnham says the teeth and jaw of the animal were too frail for a grab-and-gulp strategy like big carnivores. Instead, it might have employed a grab-and-hold technique, like the Gila monster of the American Southwest.

Prof. BURNHAM: They grab onto you and they don't let go. So they just get a vise grip on your hand or whatever they can grab from you, and that's enough to get the venom into your tissues.

JOYCE: The animal essentially chews the venom into the wound. Burnham describes sinornithosaurus in the Proceedings of the National Academy of Sciences. He can't tell what kind of venom the creature might have had. But if it were like the rear-fanged venomous animals alive today, he thinks it would immobilize rather than kill, so its prey could be eaten more leisurely.

Prof. BURNHAM: They lived in these forests, most probably lived in trees, or hunted from trees anyways. And so anything that they could get a hold of, perhaps a small lizard or mammal as well, would be just fine.

JOYCE: The debut of a new kind of dinosaur, especially one so radically endowed, usually brings out skeptics. Paleontologist Tom Holtz of the University of Maryland says he's not convinced yet.

Professor TOM HOLTZ (Professor of Paleontology, University of Maryland): They give a number of different physical features which they interpret as signs of poison or poison delivery systems, but which, in my opinion, are more easily interpreted in other types of biological contexts.

JOYCE: For example, Holtz says many dinosaurs have a cavity in their jawbone, probably to hold an air sac for cooling. He says the grooves could be something else, maybe wear and tear. But Burnham says he's found more fossils with grooved teeth. He says that when he goes back to China, he'll be looking at dinosaur teeth a lot more closely than he used to.

Christopher Joyce, NPR News.

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