New evidence of Microraptor's hunting ability came from fossilized remains in China, the University of Alberta reported Monday.
"We were very fortunate that this Microraptor was found in volcanic ash and its stomach content of fish was easily identified," paleontology graduate student Scott Persons said.
Until now paleontologists had believed Microraptors -- about the size of a modern day hawk -- lived in trees where they preyed exclusively on small birds and mammals.
But analysis of the new fossil revealed its teeth were adapted to catching slippery, wiggling prey like fish, the Alberta researchers said.
"Now we know that Microraptor operated in varied terrain and had a varied diet," Persons said. "It took advantage of a variety of prey in the wet, forested environment that was China during the early Cretaceous period, 120 million years ago."
This is the first evidence of a flying raptor able to successfully prey on fish, the researcher said, with Microraptor's wings configured something like a biplane.
"It had long feathers on its forearms, hind legs and tail," said Persons. "It was capable of short, controlled flights."