Research suggests the Sinocalliopteryx gigas, a small carnivorous dinosaur found in northeastern China, was likely a ruthless and efficient hunter with a voracious appetite.
The theory is contained in a report published Wednesday in the journal PLOS ONE. The authors, led by Phil Bell of the Alberta-based Pipestone Creek Dinosaur Initiative, investigated the abdominal contents of two specimens of Sinocalliopteryx gigas.
The creature was about two-metres long and weighed about 20 kilograms. It ran on its hind legs and had long forearms with three sharp claws. One specimen appeared to have eaten a bird-like dinosaur, and the other’s abdominal cavity contained the remains of at least two primitive birds.
"Now these dinosaurs were not flying so if we assume the other option then these animals were pretty nifty hunters," Bell said.
"You can imagine it stalking its prey through the underbrush and leaping up and catching birds on the wing or nabbing them from their perch on a tree."
Bell said it is extremely rare to discover what dinosaurs were actually doing millions of years ago.
"We know what they looked like for the best part but really what they fed on and how they were doing that and interacting with other animals is hard to come by," Bell said.
"The coolest thing about this find is that we're looking at the belly of the beast. We're seeing exactly what this animal ate right before it died."
The abdominal contents reveal Sinocalliopteryx gigas fed on some pretty nasty critters.
"In this case we've got primitive birds and also small meat-eating dinosaurs that were relatives of the Velociraptor," he said.
Bell said it is likely that the specimens died within a day of eating due to the partial digestion of the fossilized stomach contents. There were a series of shallow lakes where the specimens were found.
Although the study doesn't rule out the possibility that Sinocalliopteryx was a scavenger, it is more likely it was a hunter.
Bell said if you look at animals today that feed on birds they've either got to fly or hunt by stealth.
"Its teeth were pretty sharp little daggers — serrated like steak knives and designed perfectly for cutting meat. They were obvious predators," he said.
"If you look at the skeleton of this animal, it's built like a runner. It's really sleekly built, almost like a cat so you can imagine it stalking its prey."