Dinosaurs Went Underground to Wait Out Extreme Weather

Brian Handwerk
for National Geographic News
July 15, 2009

Sure, the dinosaurs went extinct. But to hang around for 165 million years, they must have known a thing or two about survival.

The recent discovery of the oldest known dinosaur burrow reveals one way polar dinosaurs adapted to extreme conditions—by going underground.

"That's one of the fascinating aspects of polar dinosaurs, we have to put them in settings where there might be snow, ice, and darkness for long periods of the year," said Emory University paleontologist Anthony Martin.

Martin discovered the 110-million-year-old burrow on Australia's southeastern coast, an area once adjacent to Antarctica (map of Earth a hundred million years ago) and rich with polar dinosaur bones.

(Also see pictures of newfound Australian dinosaur species.)

Small Dinosaurs, Subterranean Survival Skills

Martin had also been part of a team that in 2006 uncovered the first known dinosaur burrow, an underground den in Montana holding a 95-million-year-old dinosaur family.

In Australia, he said, he was shocked to find a burrow that, while empty of fossils, is nearly identical to its U.S. counterpart.

The six-foot-long (182-centimeter-long) by (31-centimeter-wide) one-foot-wide burrow is carved into an early Cretaceous outcrop. (The Cretaceous period lasted from about 145.5 to 65.5 million years ago.)



Video: Paleontologist Presents Australian Dinosaur Burrows

Because of the burrow's age, shape, size, and other characteristics, Martin believes the den's dwellers were small ornithopods, each about the size of a large iguana and able to stand upright on its hind legs.

The plant-eaters reached their subterranean chamber by descending a spiraling passage that had been dug into a riverbank—long since turned to rock—on a forested plain.

Global Tactic?

The new den discovery suggests that similar dinosaur species on opposite ends of the Earth dug burrows for millions of years.

In the warmer climes of ancient Montana, dinosaurs probably dug burrows primarily to protect their young, Martin said.

But Australia's formerly extreme weather might have made the technique especially attractive to the down-under diggers—and perhaps to undiscovered dinos elsewhere.

"Right now burrowing dinosaurs might look like an exception to the rule," he said. "But I wouldn't be surprised if more species [dug burrows]. Ten years from now it might be considered commonplace."

Findings published in this month's issue of the journal Cretaceous Research.

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