EDMONTON - Alberta paleontologists are hailing a newly found pint-sized predator that is considered to be the smallest meat-eating dinosaur ever discovered in North America.

But don't let the diminutive stature of Hesperonychus fool you. This miniature version of the two-legged velociraptor was a tiny terror in the forests and swamps of southern Alberta around 75 million years ago.

"It was half the size of a domestic cat and probably hunted and ate whatever it could for its size -- insects, mammals, amphibians and maybe even baby dinosaurs," Nick Longrich of the University of Calgary said Monday.

"Until now, the smallest carnivorous dinosaurs we have seen in North America have been about the size of a wolf."

The findings of Longrich and colleague Philip Currie of the University of Alberta in Edmonton were to be published Tuesday in the Proceedings of the National Academy of Sciences.

The paper contends that such small carnivorous dinosaurs were much more numerous and played a more important role in the ecosystem of the Cretaceous era than scientists have realized.

The two men's research is based on fossilized claws and a pelvis that were collected in 1982 by paleontologist Betsy Nicholls from Dinosaur Provincial Park in southern Alberta. The bones were stored in a drawer for 25 years before Longrich and Currie began studying them in 2007.

"Judging by the amount of material we collected, we believe animals the size of Hesperonychus must have been quite common on the landscape," Longrich said.

"For the past 100 years we've completely overlooked a major part of North America's dinosaur community."

Hesperonychus means "western claw" -- a reference to a sickle-shaped claw on each of its two hind limbs that it used to impale and slash at its prey.

In the past, many scientists believed such smaller fossils came from baby dinosaurs or juveniles -- not small adults.

Longrich said historically there's been more scientific interest in larger dinosaurs such as Tyrannosaurus rex because it was thought that they made more interesting display specimens.

Smaller dinosaurs were also more likely to have been eaten by larger animals, making it less likely to find intact skeletons. The bones of smaller species were also more prone to be washed away.

Finding fossils of creatures such as Hesperonychus is more challenging, because the tiny bones are harder to see.

The publicity surrounding the discovery of similar specimens in China a few years ago has made researchers more aware of what to look for.

"To find something this small you have to get down on your hands and knees. Once I knew what to look for, I started seeing them everywhere."