Paleontoriano

University of Alberta researchers used fossilized teeth to identify at least 23 species of small meat-eating dinosaurs that roamed western Canada and the United States, 85 to 65 million years ago.

Until now, only seven species of small two-legged meat-eating dinosaurs from the North American west had been identified.
U of A palaeontologist Philip Currie and student Derek Larson examined a massive dataset of fossil teeth that included samples from members of the families to which Velociraptor and Troodon (possibly the brainiest dinosaur) belong.

"Small meat-eating dinosaur skeletons are exceedingly rare in many parts of the world and, if not for their teeth, would be almost completely unknown," said Larson.
The researchers say the huge increase in the number of small meat-eating species to 23, shows that instead of a few species existing for many millions of years, there were actually many small meat-eating species, each existing for shorter periods of time.

"We can identify what meat-eaters lived in what geographic area or geologic age," explained Currie. "And we can do this by identifying just their teeth, which are far more common than skeletons."

Source: Sciencedaily