The ancient bones belong to Gallimimus bullatus, a species of bipedal dinosaurs in the group ornithomimids, or bird mimics.
Primitive ornithomimids, which appeared about 130 million years ago, had teeth, says Makovicky.
The gastroliths, or stomach stones, that have been found in some ornithomimids provide another clue that the creatures didn't consume large animals, says Makovicky.
Furthermore, ornithomimids couldn't have gotten their nourishment from fleshy fruits because plants that bore them hadn't yet evolved, says Dale A.
A new study, led by paleontologists Darla Zelenitsky from the University of Calgary and Francois Therrien from the Royal Tyrrell Museum of Palaeontology, described the first ornithomimid specimens preserved with feathers, recovered from 75 million-year-old rocks in the badlands of Alberta, Canada.
"Furthermore, despite the many ornithomimid skeletons known, these specimens are also the first to reveal that ornithomimids were covered in feathers, like several other groups of theropod dinosaurs," the researcher added.
The researchers found evidence of feathers preserved with a juvenile and two adults skeletons of Ornithomimus, a dinosaur that belongs to the group known as ornithomimids.
But the discovery of these ornithomimids in sandstone shows that feathered dinosaurs can also be preserved in rocks deposited by ancient flowing rivers," noted Therrien.