A Venomous Dinosaur

Dec 22, 2009 1:53pm

Sinornithosaurus millenii was probably no bigger than a turkey, a winged dinosaur that lived about 125 million years ago in what is now northeastern China.

What makes it striking is that it probably had venom in its bite.  A team from the University of Kansas, writing in Proceedings of the National Academy of Sciences, examined its skull and reports that it had grooves in its teeth, the way some modern snakes do.  (It's "vg" in the skull diagram below if you click on it to enlarge.) Though there is no flesh in the fossil remains, it appears there was a space in the upper jaw ("sff" in the diagram) that could have contained a venom pouch.

A venomous dinosaur, eh?  This is the first published evidence of one.  Preschoolers grow up thinking of dinosaurs as giant lizards, and paleontologists have been saying for a generation that they were probably evolutionary cousins of modern birds.  But the two together?  It so happens "Sinornithosaurus," the name for this one, means "Chinese bird-lizard."

So how did it operate? The authors say it probably lived in forests, feeding on the many birds of the Early Cretaceous period.  Like modern rear-fanged snakes, the researchers say it probably used the venom to stun rather than kill.

“You wouldn’t have seen it coming,” said David Burnham, one of the co-authors of the paper. “This guy has feathers all the way down to its feet.  It would have been at home in the trees.  It would have swooped down behind you from a low-hanging tree branch and attacked from the back. It wanted to get its jaws around you. Once the teeth were embedded in your skin the venom could seep into the wound. The prey would rapidly go into shock, but it would still be living, and it might have seen itself being slowly devoured by this raptor.”Beyond the ick-factor, why does this matter?  Because, says Burnham, it makes the prehistoric world more dangerous and more complex."Venom is primitive," he said on the telephone.  "So the question is not, 'Who had venom?'  It's, 'Who didn't?'"It's making the world a far more poisonous place than we thought."

(Artist's conception by Robert DePalma/University of Kansas. Skull image courtesy of National Academy of Sciences.)

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