COLVILLE RIVER, Alaska -- Dallas Museum of Natural History curator Tony Fiorillo returned to Alaska's North Slope in July, intent on extracting the skull of a pachyrhinosaur spotted last summer north of America's northernmost mountains.
The plant-eating dinosaur was a cousin to triceratops. It grew up to 7-feet high and 18-feet long. Its head had a boney nasal protuberance that may have supported a horn, and a prominent frill at the back with two distinct horns.
Fiorillo never did extract the skull. As the dinosaur hunters began to work, they found seven more pachyrhinosaur skulls in an area of about 13-feet by 13-feet.
''We never would have predicted finding that much,'' Fiorillo said. They ended up covering parts of three skulls with a burlap and plaster cast and hauling them out.
Only a few decades ago, most paleontologists imagined din-osaurs as tropic and subtropic animals with reptile physiology, and that Alaska was too far north to yield remains. But scientists relying heavily on volunteers are slowly unlocking the Arctic's life history secrets, including a rich dinosaur heritage.
Eighteen miles upstream from Fiorillo's pachyrhinosaurs, hunkered near the bottom of a 100-foot-high bluff on the Colville, University of Alaska Museum paleontologist Kevin May feathered grit away from fossilized bones of juvenile hadrosaurs, duckbilled, plant-eating dinosaurs that grew 10-feet tall and 40-feet long.
''Our working theory is that this was a group of animals that was crossing a stream during flood stage, and they got caught in the higher water and drowned,'' May said.
Later, under a lean-to heated by camp stoves, he covered the smooth, brown fossil legs and joints with latex. Peeled off, the latex mold will be cast for a museum display.
The fossils are part of the Liscomb bed, which runs up to 3 feet high for the length of two football fields along the Colville bluff. How deep the bones run into the hillside, no one knows.
There are so many fossils, the dinosaur hunters don't even bother with the odd pieces below on the beach, where the next flood stage will make them rolling stones on the river bottom.
Overseeing the work was Roland Gangloff, curator of earth sciences for the University of Alaska Museum in Fairbanks.
''If I'm right,'' Gangloff said, ''this is going to be one of the densest bone yards ever.''
Paleontology is in its infancy in Alaska, pursued methodically only since the mid-1980s when the fossil bed discovered by Shell Oil geologist Robert Liscomb drew interest at universities.
A dozen Alaska dinosaurs have been identified, all alive in the late Cretaceous period, the last slice of the more than 150 million years when dinosaurs walked on Earth.
Most Alaska have been recovered north of the Brooks Range near Ocean Point, 25 miles from the Arctic Ocean in the northeast corner of the National Petroleum Range Alaska.
What cold-blooded dinosaurs were doing so far north is a question that drives the researchers -- and makes them question whether the animals were cold-blooded.
The climate was far milder than present-day northern Alaska, where the daily minimum temperature is below freezing 297 days each year. During dinosaur days, plant fossils and other evidence indicate that the climate was more like Washington's Olympic Peninsula, covered with trees but cold enough so that cold-blooded creatures would need winter protection, Gangloff said.
That means Alaska's hadro-saurs either migrated south, or hibernated -- or were warm-blooded. Conspicuous by their absence are fossils of known cold-blooded creatures such as lizards or crocodilians, which have been abundant in Montana and Alberta.
Then there's the big question: Can Alaska fossils give any clues as to what killed the dinosaurs 65 million years ago?
Hadrosaurs, lunch meat for carnivores, lived from Alaska to Australia and Antarctica. The ability of hadrosaurs to adapt to cold leads some paleontologists to question whether a single catastrophic event, such as a large meteor hitting the earth, kicking up dust, blotting out the sun's rays and lowering the planet's temperature, would wipe out all dinosaurs.
Alaska's earth scientists want to find out, but face daunting challenges, starting with the remote, roadless locations of fossil beds.
From the air, the tundra looks flat and smooth, belying what's below: miles upon miles of tussock, the mushroom-shaped mounds a foot or so high that bend underfoot like rubber stumps. Between them is bog. The only practical summer mode of transportation is by air, adding to the expense of reaching dig sites.
Snow stays until early June. Federal law prohibits disturbing nesting raptors such as peregrine falcons. Drenching rains turn dig sites into clay soup, driving researchers into their tents to wait for dry weather.
Over the last 16 years, Gangloff said, the field season on the Colville has averaged just 12 summer days.
On sunny days, biting insects swarm in clouds, driving caribou batty and researchers to their knees, praying for a strong breeze.
Gangloff has traveled to the Colville for 14 summers. The researchers cobble together small grants to provide camps for volunteers -- from university faculty to school children to professionals who pay their own way -- willing to kneel and dig in bone beds.
''It's been about 85 percent volunteer,'' he said.
This year Gangloff and Fiorillo received local help: heavy-lifting Chinook helicopters from the Army's 4th Battalion, 123rd Avia-tion Regiment at Fort Wainwright in Fairbanks.
Ostensibly training to fight terrorists attacking North Slope oil fields, the soldiers in the big helicopters ferried in supplies, then carried out specimens, including the casting with the three pachyrhinosaur skulls, which weighed more than 2,200 pounds.
On the ground, 10 California teachers helped dig. A National Science Foundation grant helped bring them up from the West Contra Costa Unified School District. They learned vertebrate paleontological field techniques. In return, they will develop curriculum, mentor other teachers and try to excite children about earth sciences.
The teachers recovered more than 500 bones and teeth and made measurements that will be use to create three-dimensional maps of the bed.
K. Christopher Beard, curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh, said Alaska's fossils are important for understanding how dinosaurs moved from Asia to North America.
Scientists also wonder, Beard said, whether Alaska dinosaurs reflect all dinosaurs or made adaptations specific to their surroundings.
''The Alaska fossil record needs to be improved,'' he said.
''They are forcing people to reconsider what dinosaurs were like,'' Beard said.
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