The newly identified creature weighed less than two pounds and stood about 4 inches tall. From head to tail, it measured a little over 2 feet long, said Luis Chiappe, director of the Dinosaur Institute of the Natural History Museum of Los Angeles County where the fossil bones are stored.
The dinosaur "would have looked like a roadrunner on steroids," Chiappe said.
It likely ate plants and hunted bugs during the late Jurassic period, about 150 million years ago. It was so tiny and fast that it probably darted between the legs of larger dinosaurs, researchers said.
Bones of four individuals - including skull, arm and leg fragments - were discovered three decades ago in Fruita in western Colorado and kept at the museum.
Chiappe and an international team recently identified and named it Fruitadens haagarorum, which incorporates where the bones were found and the name of the president of the museum's board of trustees, Paul Haaga.
A description of their work appears Wednesday in the British journal Proceedings of the Royal Society B: Biological Sciences.
Earlier this year, Canadian researchers reported that a chicken-sized dinosaur weighing in at 4-to-5 pounds was the smallest meat-eating dinosaur yet discovered in North America.