Smallest Dinosaur in North America Discovered

Ker Than
for National Geographic News
September 25, 2008
A chicken-size dinosaur with a taste for termites was the "anteater" of its day and may be one of the smallest dinosaurs ever discovered in North America, scientists say.

The new species, dubbed Albertonykus borealis, is a member of an unusual-looking dinosaur group known as the Alvarezsaurs, which have also been found in Asia and South America.

About a dozen arm and leg bones dated at 70 million years old were found in Alberta, Canada, in 2002 but have only recently been analyzed.

Bizarre Creatures

"They're really freakish animals," study co-author Nick Longrich, a paleontologist at the University of Calgary in Canada, said of Albertonykus.

(See other bizarre creatures from the Cretaceous period.)

Alvarezsaurs generally had long tweezerlike snouts, slender birdlike legs, long rigid tails, and stumpy, Tyrannosaurus rex-like arms.

At 2.5 feet (0.7 meters) long, the newfound dino is the smallest Alvarezsaur ever found in North America, Longrich said.

Proportionally, its arms were as short or shorter than T. rex's, but much more powerfully built.

"They look like the forelimbs of a mole," Longrich told National Geographic News.

But unlike moles, Albertonykus's arms would not have been useful for digging. Its hand had only two stunted fingers and a massive picklike thumb.

The team speculates that Albertonykus dined on insects, and that it used its large thumb claw to tear open rotten logs packed with termites and other critters.

Skull fragments of other Alvarezsaurs found in Asia suggest Albertonykus had a long snout filled with tiny teeth similar to those of certain insect-eating mammals alive today, such as armadillos and some species of anteaters, Longrich said.

He and colleagues describe the dinosaur in the current issue of the journal Cretaceous Research.

Ancient Migrations

Hans-Dieter Sues is a paleontologist at the Smithsonian National Museum of Natural History in Washington, D.C., who was not involved in the study.

Sues said the new discovery underscores the movement of Alvarezsaurs and other different dinosaur groups between East Asia and North and South America.

"It's a North American record of these creatures, which we previously had only a few isolated bones of," he said.

As for Albertonykus's small size, it's possible the specimens the researchers analyzed had not yet reached adulthood, Sues said.

"The key thing to determining whether a dinosaur is a youngster or a really tiny adult is to see vertebrae, because the different parts only fuse at maturity," he said.

"In this case, it may simply be that they are small individuals that are not fully grown yet."

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