March 17, 2009

Paleontologists Discover Chicken-Sized Dinosaur

Canadian paleontologists have discovered the remains of the smallest meat-eating dinosaur known to roam North America.

Hesperonychus elizabethae looked like a Velociraptor, but the carnivorous mini-dinosaur found in the swamps and forests of southern Alberta was barely the size of a chicken "” weighing only around 4-to-5 pounds.

Nicholas Longrich of the University of Calgary said it probably hunted and ate whatever it could for its size "” insects, mammals, amphibians and maybe even other small dinosaurs.

Longrich said the bones of the tiny dino were found mixed in with fossils that had been collected a quarter-century ago and remained in a museum drawer.

"Until now, the smallest carnivorous dinosaurs we have seen in North America have been about the size of a wolf," said Longricj, who suggested that animals the size of Hesperonychus, which means "western claw," must have been quite common on the landscape.

Standing around 19 inches tall, Hesperonychus ran on two legs and had razor-sharp teeth and a large sickle-shaped claw.

Longrich said when they first came across the fossils they initially assumed the claws came from juvenile raptors because of their miniscule size.

"But when we studied the pelvis, we found the hip bones were fused, which would only have happened once the animal was fully grown," he said.

Paleontologists in China have found similar-sized dinosaur fossils over the last few years, and studying those helped the researchers identify this North American version.

Longrich said the find emphasizes how little we actually know, and it raises the possibility that there are even smaller fossils out there waiting to be discovered.

"Small carnivorous dinosaurs seemed to be completely absent from the environment, which seemed bizarre because today, the small carnivores outnumber the big ones," he said.

"It turns out that they were here and they played a more important role in the ecosystem than we realized. So for the past 100 years, we've completely overlooked a major part of North America's dinosaur community."

Last year, Longrich and University of Alberta paleontologist Philip Currie and described the previous record-setting small North American dinosaur, a chicken-sized insectivore named Albertonykus borealis.


Image Caption: Hesperonychus claw compared to a Canadian quarter. (University of Calgary)


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