By examining the sediments and plant fossils associated with their hypsilophodontid finds, the researchers have pieced together a climatological and environmental record of southern Australia during the dinosaurs' reign from about 115 to 105 million years ago.
"Many of the trees didn't slow down to the point of dropping leaves," Vickers-Rich said. "They didn't shut down, so there was food around for the animals. In fact, the climate, other than the light, might well have been like Seattle."
Located in the Pacific Northwest, Seattle is well known as wet, dreary, and mild. Temperate rain forests flourish. Snows blanket the nearby mountains.
Other dinosaurs from southern Australia include Serendipaceratops arthurcclarkei, one of the oldest horned, or frilled, dinosaurs known, which suggests that horned dinosaurs may have originated in the southern polar region.
"That group is most well known from Mongolia, where Protoceratops occurs in the very late Mesozoic/late Cretaceous. The material of Australian origin is early Cretaceous," Vickers-Rich said.
Hammer said Cryolophosaurus ellioti, the 190-million-year-old meat-eating dinosaur he found in Antarctica, "is a very old relative of the well-known Allosaurus from North Americawhich is from the late Jurassic, about 150 million years ago."
Most recently, in December 2003, while Hammer and his colleagues were continuing excavation of the Cryolophosaurus ellioti specimen they found in 1991, their mountain safety guide stumbled upon a sauropod dinosaur. It may turn out to be the largest dinosaur ever found in Antarctica.
The specimen is currently en route to the U.S., where Hammer and colleagues will analyze it later this year.
Since the mid 1980s Roland Gangloff, a paleontologist with the University of Alaska Museum, has uncovered several dinosaurs along Alaska's North Slope. The dinosaurs found there closely resemble the mix of dinosaurs from regions farther south in Alberta, Montana, and Wyoming, with the notable exception of truly cold-blooded reptiles such as lizards and crocodiles.
The lack of cold-blooded reptiles leads Gangloff and others to argue that their dinosaurs may have been neither truly warm nor truly cold blooded, but rather possessed a unique type of metabolism unlike any animals alive today.
Dinosaur hunting in the polar regions is strenuous and expensive work, especially in Antarctica, where Hammer and his colleagues endure temperatures that regularly dip to -25 degrees Fahrenheit (-32 Celsius), live in tents, and melt ice for drinking water.
"The sites are very inaccessible. We are 500 miles [800 kilometers] inland from the coast and about 400 miles [640 kilometers] from the geographic South Pole," Hammer said. "They are also at high altitudethe dino locality on Mount Kirkpatrick [where we found the sauropod] is at about 13,000 feet [4,000 meters]."
In Australia, where today the climate is temperate and most of the continent is accessible, Vickers-Rich and crews had to dangle 300 feet (100 meters) or more off a cliff before tunneling into it to get at the dinosaur bones. "Work in Australia is anything but benign," she said.
The fruits of the dinosaur hunters' labors will be on display at the Burke Museum in Seattle until October 10, 2004.
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