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University of Calgary researcher Nicholas Longrich sits with a model of tiny dinosaur, which likely weighed less than two kilograms. ((University of Calgary))

It had razor sharp claws and its teeth may have been the terror of Alberta 75 million years ago — among animals smaller than a squirrel, that is.

The kitten-sized predator identified by paleontologists at the University of Calgary and the University of Alberta is the smallest carnivorous dinosaur ever found in North America. The next smallest meat-eating dinosaur ever found on the continent was about the size of a wolf.

"Until we found this animal, basically we had no evidence for any small carnivores being present in North America," said University of Calgary researcher Nicholas Longrich, in a video released by the university on Monday.

Longrich and the University of Alberta's Philip Currie have written an article describing the velociraptor-like dinosaur, published Monday in the Proceedings of the National Academy of Science.

The tiny, bird-like predator ran on two legs and was about half the size of a housecat, weighing less than two kilograms, and standing about as tall as an average wastebasket. It likely hunted near the ground in marshes and forests for insects, small mammals, amphibians and "maybe even baby dinosaurs," Longrich said.

The researchers have given the dinosaur the scientific name Hesperonychus elizabethae.

Hesperonychus means "western claw" and elizabethae is a tribute to the late Elizabeth (Betsy) Nicholls, the well-known Alberta paleontologist and former curator at the Royal Tyrrell Museum in Drumheller who originally unearthed the bones.

Found 20 km from Dinosaur Provincial Park

Nicholls found the fossilized claws and a well-preserved pelvis in 1982 at the Dinosaur Park Formation, about 20 kilometres east of Dinosaur Provincial Park, or about 140 kilometres east of Calgary. Longrich said he was going through the collections at the University of Alberta when he stumbled across the bones less than two years ago.

Previously, paleontologists believed they belonged to a juvenile dinosaur of some sort.

Longrich noticed that one of the bones looked like the hip bones of some velociraptor-like dinosaurs excavated in China. Those Chinese dinosaurs were a little less than a metre long.

On closer examination, Longrich noticed that the pelvic bones had fused together — something that happens after the animal stops growing, indicating that it was an adult.

Because quite a number of bones were found, the researchers suggest that Hesperonychus was an important part of the ecosystem in the late Cretaceous period, as small predators such as cats and foxes are an important part of the ecosystem today.

The results also show for the first time that tiny velociraptor-like dinosaurs lived not just in China, but also in North America, and that such dinosaurs continued to roam Earth about 45 million years longer than previous records suggested.

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Bones from the feet and claws that are believed to belong to Hesperonychus were unearthed near Dinosaur Provincial Park in 1982. ((Courtesy of the National Academy of Sciences, PNAS))