In hot pursuit of polar dinosaurs

Standing on a low bluff overlooking the Pacific Ocean, paleontologist Tom Rich pauses. "This is pretty civilized for a fossil dig," he admits.

He and his team sleep in a resort town. They spend hours on the beach slathered in sunblock. When it gets too hot, they cool off in a tide pool nearby.

Yet, this is hardly a vacation. The team is sifting for clues about some of the least-understood creatures of prehistory: polar dinosaurs.

Some 115 million years ago, long before Tyrannosaurus Rex was a glint in anybody's eye, dinosaurs roamed what is now southeastern Australia, which at the time lay well within the Antarctic Circle. Now, their remains - unearthed on this narrow stretch of beach two hours southeast of Melbourne - are contributing to the most species-rich collection of polar dinosaur fossils in the world. And they're opening new windows on how these ancient animals adapted to frigid climates, and why some survived in one of the world's most isolated regions while their kin had died out elsewhere.

The site also challenges the ingenuity of archaeologists who, instead of scratching for fossils in an arid wasteland, pack up every time the tide comes in, then pump out their dig and begin again.

Indeed, discovery of the surprising diversity of creatures that existed here between 115 million and 105 million years ago - particularly the dinosaurs - is perhaps the most important result to come out of the work done in the region, says Hans-Dieter Sues, associate director for research and collections at the National Museum of Natural History in Washington.

"The fact that this very diverse assemblage of vertebrates was living in what at the time were really high latitudes has important implications," he says. "Dinosaurs were coping with this extreme environment. This flies in the face of the now-ancient notion that dinosaurs were just overgrown reptiles" in tropical settings.

At the time, this region had a climate closer to that of Fairbanks, Alaska, than to, say, tropical Cairns, Australia. Dr. Rich's site was part of a vast river-laced valley formed as Australia and Antarctica began to part company. Thus, some of the region's creatures show evidence that they hibernated or otherwise slowed their body processes in the winter. Others appear to have been active all year, their eyes larger than others' in order to function in winter darkness.

From the work here at Flat Rocks, outside Inverloch, and at Rich's previous site at Dinosaur Cove, west of Melbourne, it appears that Australia served as a retirement home for over-the-hill dinosaurs. "These polar environments are places where animals could go and be safe, and last when they were being wiped out at lower latitudes," says Rich, curator of vertebrate paleontology at Melbourne's Victoria Museum. But new species "also could be generated here."

The coexistence of dinosaurs and mammals in such extremes is raising questions about just how wildly the climate varied and the range of mechanisms creatures developed to cope with such changes.

As evidence of the wide swings, Rich takes a visitor to a thick petrified tree trunk jutting from the rock shelf, suggesting that a temperate forest thrived here at one point. Just 200 yards away, he shows soil layers at the base of the bluff that indicate permafrost, evidence for tundra-like conditions at another stage.

"We don't know if some of the animals we find lived here all the time, or whether they migrated in and out as climate shifted from warm to cold periods," Rich says.

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