March 17, 2009 / 12:08 AM / 10 years ago

Researchers ID North America's smallest dinosaur

CALGARY, Alberta (Reuters) - Canadian researchers said on Monday they have discovered North America’s smallest known dinosaur, a pint-sized predator half the size of a house cat and cousin to the ferocious Velociraptor, which roamed in what is now Alberta 75 million years ago.

Hesperonychus, whose name means "western claw", in an illustration courtesy of the University of Alberta. REUTERS/University of Alberta/Handout

Hesperonychus, whose name means “western claw”, prowled southeastern Alberta in Western Canada during the late cretaceous period, running on two legs, eating insects, small mammals, or whatever else it could find.

Researchers said the dinosaur resembled its cousin Velociraptor, a hunter with a fierce reputation and a killer claw similar to that of Hesperonychus.

“It was only about half the size of a Velociraptor,” said Nick Longrich, a researcher at the University of Calgary, and co-author of a paper on Hesperonychus with University of Alberta paleontologist Philip Currie.

“Presumably Velociraptors could take down large animals but in this one the blade-like claw on the foot is not that big. My guess is that it was a small-game hunter, taking down mammals and birds and baby dinosaurs.”

Hesperonychus fossils have been collected since 1982 but paleontologists had assumed that because of their small size, they must have come from juvenile animals.

However Longrich concluded that the dinosaur was full grown at a height of 50 centimeters (20 inches) after studying a fossilized pelvis and seeing that the hip bones were fused — a sign it was an adult.

The 2-kilogram (4.4 pound) creature supplants the chicken-sized insectivore Albertonykus Borealis as the smallest known dinosaur in North America, though smaller species have been found in China.

Longrich suspects, however, that there are more fossils of tiny meat-eating dinosaurs waiting to be found, especially since today small carnivores outnumber bigger predators.

“My gut says that when we take a good close look at the fossil record we’ll start to see this kind of animal in a lot of different places,” he said.

Longrich and Currie’s paper was published on Monday in the advanced online edition of the Proceedings of the National Academy of Sciences at www.pnas.org

Editing by Peter Galloway

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