It may have been small, but the newly identified dinosaur was fierce.
The 75 million-year-old fossil skull, found by paleontologist Robert Sullivan in New Mexico in 1999, was thought to be from a species of raptor found in what is now Montana and Alberta - part of a family of swift, powerful predatory dinosaurs like the Velociraptor.
But Steven Jasinski, a doctoral student at the University of Pennsylvania, found some subtle, but significant, differences.
This dinosaur, which he named Saurornitholestes sullivani, had an unusually large area of its skull where the brain's olfactory bulb would be. That meant this species "had a relatively better sense of smell... This keen olfaction may have made S. sullivani an intimidating predator as well."
S. sullivani, which lived around the end of the age of dinosaurs, is the only named creature from this period found in the southern part of North America. It was less than a meter high at its hip, and about 2 meters from head to tail. Jasinski suggested that it was agile and fast, perhaps hunting in packs - "not a dinosaur you would want to mess with."
Jasinski's findings are reported in this month's New Mexico Museum of Natural History and Science Bulletin.