
A fossil cast of what's believed to be a Sinornithosaurus is seen at the American Natural History museum in New York in this file photo.
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 fossil in a museum - specifically, by its upper teeth.
"We finally realized that we're looking at the outside of these teeth and they're grooved," Burnham recalls. "And we both looked at each other and thought,
'What? Why would an animal have grooved teeth?' "








