To understand why Phil Currie stands shaking on top of a ridge in a desolate Canadian wilderness, contemplating whether to drag himself to the next ridge hundreds of yards away and risk dying of dehydration or to turn back, you need to know only one scene from his childhood: He is six years old, sitting at the kitchen table. He opens a box of Rice Krispies and out plops a plastic dinosaur. Imagination shifts into high gear and the rest of little Phil's life is defined in a moment by creatures that have never been seen by humans. "I was hooked," he says. "They were real. They weren't mythology. They were the biggest, the strongest, the fastest."
So that is why he is here, in Alberta's badlands, with the temperature pushing above 105, shading his eyes against the searing sun with one hand and thrashing at blackflies with the other, studying the desolate landscape of fissured earth.
He opens a leather satchel and pulls out a photograph taken by another fossil hunter nearly 90 years earlier. He looks at the ridge, looks at the photo, looks at the ridge. "You shouldn't do it," he mutters to himself. "That's just nuts. You should go back to camp." Indeed the rest of his group, including his wife, had turned back hours ago.
"For about 15 minutes I kept talking to myself," he remembers. " 'Should I do it? Should I not do it?' I finally decided I had to try." Currie believed the ridge ahead was worth the risk because it might be the site of a nearly forgotten treasure trove of dinosaur bones. And those old fossils could bolster his theory that two-footed carnivores like Tyrannosaurus rex and Albertosaurus traveled in packs, with fleet youngsters driving prey into the powerful jaws of waiting adults.
"Most people have thought of carnivores, especially the big ones, as solitary animals," Currie says. "The idea of ten or so tyrannosaurs coming at you at once is much more scary than thinking about just one. Not so much because of the adults but because of the juveniles. They would have been fast, nasty little animals."
Perhaps Currie's vision was prompted by the fact that he himself is so nimble. At 50, he still delights in planting his hiking boots at the top of a 100-foot, 60-degree sandstone slope and skiing down in a cloud of dust. And he is relentless, a hardened adventurer who always goes on to the next ridge. "Phil is driven," says Bruce Naylor, director of the Royal Tyrrell Museum in Drumheller, Alberta, where Currie is a staff paleontologist. Currie's wife, paleobotanist Eva Koppelhus, sums him up with one word: determined.
"I love the detective aspect of trying to understand something that isn't around anymore," he says. "And when you suffer some of these, well, hardships--sun, heat, rain, bugs, cold--you have a better appreciation for life." Particularly forms of life that vanished eons ago.
Long drawn to tyrannosaurs "because they were so dynamic and came in many varieties," Currie is perfectly located in the badlands that stretch from Alberta down through Montana and Wyoming. The area is prime ground for fossil hunters seeking tyrannosaurs, including the 40-foot-long, seven-ton T. rex and the slightly smaller Albertosaurus. The region was also once home to the sharp-clawed and birdlike Velociraptors, ostrich mimics such as Ornithomimus, and duck-billed plant eaters called hadrosaurs.
Most tyrannosaur skeletons recovered over the years from the badlands have been found in isolation, reinforcing the traditional view that they were solitary hunters or scavengers. To prove otherwise, Currie needed to find a site offering clues to interaction among tyrannosaurs, which is why he tried to find that elusive next ridge, the one paleontologist Barnum Brown had walked along back in 1910.
Brown, dubbed Mr. Bones by newspaper reporters early in the century, had discovered the first known Tyrannosaurus rex in 1902. On one of many expeditions sponsored by the American Museum of Natural History in New York, Brown followed the Red Deer River through the Alberta badlands and opened a small quarry on the side of a ridge. There he collected several bones from what he described as young tyrannosaurs and ostrich mimics. He intended to return to the quarry, but farther downstream he happened upon an area littered with so many dinosaur bones it kept him occupied for years to come. That fossil-hunting ground, now known as Dinosaur Provincial Park, is the source of many of the dinosaur skeletons in various museum collections around the world.
During a visit to the New York museum's collections in 1996, Currie rummaged through the basement in search of bones Brown had collected at the abandoned quarry. "Brown said he'd collected both juvenile tyrannosaurs and some ornithomimids," he says. "We don't have a lot of juvenile material, so I was pretty interested." Currie did not expect to be surprised. "I pulled open one tyrannosaur drawer and said, 'Hey, these aren't tyrannosaurs! They're ornithomimids.' Then I compared them with bones in another drawer and realized, 'No, these are actually baby tyrannosaurs!''' Although the two groups of animals are related, the ostrich-mimic bones are smaller, and the jaws lack teeth--a feature no tyrannosaur would be without.
More interesting, there were grown-up tyrannosaurs as well as youngsters. The mixture opened up possibilities. There was the chance, with a group of beasts, to learn about something that had been difficult for paleontologists to get a handle on: social lives. Activity, unlike bones, doesn't fossilize, but if the beasts died together, they may have lived together as well, and Currie thought he had a chance to dig up some clues about group interactions. "I just knew Brown couldn't have excavated all the remains and that there must be more," Currie says. "So I knew we had to find the site."
Unfortunately, Mr. Bones didn't leave much for Currie to go on. "Brown wasn't very good at keeping field notes, and he was exceptionally bad that year," Currie says. "He'd lost his wife to scarlet fever just before he went into the field, so he wasn't really concentrating."
Currie did have two photographs. One was of the camp. And the other was of the site itself. There were also some vague descriptions in letters Brown had sent to Henry Fairfield Osborn, his boss at the museum. "My dear Professor Osborn," Brown had scrawled on some notepaper with museum letterhead. "We are camped at last for about a week about 40 miles above Fox Coulee. . . . We have taken four good hind limbs and lots of caudal vertebrae [tailbones] and some jaw material of Albertosaurus. . . . "
By the summer of 1997, Currie and Koppelhus were ready to go. They had arranged a trip down the Red Deer with the Dinamation International Society, a nonprofit exhibition, research, and education company. The company supplied a dozen or so volunteers, rubber rafts, tents, and food. On August 1 the expedition started at a site called Content Bridge, 60 miles northwest of Drumheller. And they began to float downstream, looking at the banks.
On the fourth day, they found remnants of the campsite where Brown had moored his tent-covered barge by the riverside. Near a place called Dry Island Buffalo Jump, where a century or so ago the natives had driven buffalo off cliffs, expedition members spotted an area that looked just like the old photo. A poplar grove had grown taller, but otherwise the profile of the hills matched. Put Brown's barge next to the bank and the scene could easily have been from 1910. "It's funny," says Currie, "but even after 80 years the main ridge hills don't change that much."
The discovery raised hopes of finding the ridge with the abandoned bone bed. During their years in the badlands, Currie and Koppelhus have become adept at spotting old digs. "You look for sharp angles," Koppelhus says. "Most of the landscape is rounded by erosion. But where paleontologists have dug, there's usually a right angle cut into a hill, with a flat surface beneath it. When you see these contours, you look around for bits of plaster and burlap that would have been used to put protective jackets over the fossils. Sometimes you can even find bits of old newspapers."
By midday, however, Currie's colleagues were so drained by the heat they were ready to abandon the search. "It was our last scheduled day in the area," he says. "We went out in the morning, and everyone underestimated how much water to bring." But when the others returned to camp, Currie pushed on: "I couldn't leave, not knowing." Finally, alone, he reached the top of the distant ridge. He looked down and saw the telltale angled cuts made by shovels. At long last, he had found Mr. Bones's fossil heap. "If it wasn't for the fact that I was so close to heat exhaustion," he says, "I would have been jumping up and down."
But he still had to get back to camp with the heat and dehydration setting in. On the way, he stopped at a river and tried bending down to unlace his boots so he could go in the water. But his legs wouldn't bend. So he sat on the riverbank for a while, inching his legs closer and closer to his body until he could undo the boots. Wading in the water revived him a bit, and he slipped into camp without anyone's noticing. Quietly he changed into a swimsuit and went back to the river to immerse himself and cool his body. Then he returned to camp. The others had gathered around Koppelhus, who was rereading Brown's old letters, scouring them for location clues. "I said, 'I found it,' " Currie remembers. "And everything just broke loose."
Last spring Currie and his researchers returned to the site for a preliminary excavation, needing to answer an important question: Was this a group of tyrannosaurs from one time and place and not some random collection of bones that had been dumped there by river currents? Currie quickly came to the conclusion that the bones were 95 percent Albertosaurus. "Normally, Albertosaurus is only 5 percent of the fauna in this area," Currie says. "With 95 percent, and all in the same state of preservation, we can be pretty sure that they were together." There were ten, one more than Brown had thought, and they ranged in size from about 15 feet long for the youngsters up to about 30 feet long for the more massive adults.
The key to understanding the interaction among the tyrannosaur youngsters and their elders, Currie says, is the different proportions of the leg bones. "The legs of baby tyrannosaurs are built with ostrichlike proportions, similar to the fast ostrich-mimic dinosaurs. So they were pretty fast," he says. When an animal is young and small, it can have long legs like stilts. But, Currie says, "it gets harder as you get bigger because the stilts tend to break. You get older, and suddenly you have to worry about weight. You add all this weight and muscle, and you have to add more bone to the thighs to support it. That's what happens in adult tyrannosaurs. It happens in humans too. Our proportions change pretty dramatically from childhood to adulthood." And, of course, we slow down.
A mixed group of fast and slow carnivores may have had different roles when hunting prey such as the cattlelike hadrosaurs. "You can't help but imagine these young tyrannosaurs cutting a hadrosaur out of a herd and driving it into the jaws of the big guys," he says. That would help solve something that has long puzzled Currie as he thought about the different Alberta dinosaurs and what ate what. An adult hadrosaur is about 35 feet long, similar in size to a big Albertosaurus. "So a lone tyrannosaur probably wouldn't go after a lone hadrosaur, let alone a big herd. But hunting packs of animals would have strategies for dealing with big herds. They would try to confuse the hadrosaurs, or separate some of them out. These tyrannosaur youngsters were sleek and mean."
Currie pauses, the scene of the hunt fading from his mind. "This is just speculation, of course. There's a whole other side to packing--for raising young. There are interesting ideas that might develop out of this." His colleague Rodolfo Coria has recently discovered a bone bed of a new species of large carnivore, closely related to Giganotosaurus, in Argentina. Currie and Coria hope that comparisons between the sites might yield further insights into social interaction.
Currie also hopes to learn what killed the tyrannosaurs along the river. It's hard to imagine a catastrophe that would wipe out a bunch of strong, dominant dinosaurs all at once. There's no sign of a big flood or volcanic ash that would tell of an eruption. So Currie is going back to the site this summer, although he hopes for a much easier trip. But as someone who divides time into chunks of millions of years, he can say, "You have to take a long-term perspective: the discomfort will stop. The challenge, the mystery, is always going to be there."
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Happy Hunting Grounds
The harsh, dry Alberta badlands in south-central Canada don't seem like the kind of place to attract hordes of dinosaurs--or any form of life besides flies and prickly pear cactus--but that's because the scenery has changed quite a bit in the past 75 million years.
"Near the end of the Cretaceous Period, this place would have looked a lot more like the Gulf Coast does today," says Bruce Naylor, director of the Royal Tyrrell Museum in Alberta. "It was lush, with lots of coastal rivers, lagoons, and an inland sea."
The wetlands attracted large tyrannosaurs such as Albertosaurus and Daspletosaurus, along with the smaller "ostrich mimic" dinosaurs and deadly sickle-clawed members of the Dromaeosaur family called Velociraptors. Running this gauntlet of carnivores were massive herds of plant-eating duck-billed hadrosaurs, many-horned ceratopsians, and tanklike, heavily armored ankylosaurs.
Conditions in the wetlands were also optimal for preserving the remains of the dead. Muddy, fine-grained riverborne sediments buried a carcass soon after the animal dropped, sealing it from the assaults of scavengers and erosion. Over time, these sediment layers hardened into sandstone and mudstone and even harder ironstone, piling on the protection. The result: A lot of entombed, intact dinosaurs, sealed and oblivious to whatever disaster befell their relatives some 65 million years ago, wiping them from the planet.
Ensuing years brought a drier, cooler Canada. Ice ages came and went. When the glaciers of the last one retreated, about 10,000 years ago, their meltwaters unleashed fast-flowing streams that cut down through Alberta's sediments like chain saws. They carved the ancient rocks into a labyrinth of steep-sided hills covered with loose rock and deep gullies branching off from central canyons.
Rains came and ground away the soft sandstone at the breakneck speed of two centimeters a year. (In the sturdy world of stone, that's like watching sugar disappear into a cup of coffee.) And with each new rainstorm, new dinosaur bones are revealed.--J. F.
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Tyrannosaur Feathers?
Paleontologists keep uncovering tantalizing evidence of an evolutionary link between dinosaurs, including the giant tyrannosaurs, and modern birds. Phil Currie and geologist Ji Qiang of the National Geological Museum in China, recently coauthored a scholarly report about two small dinosaurs--Caudipteryx and Protarchaeopteryx--that had what looked, for all intents and purposes, like feathers. "These two new animals are part of a group of dinosaurs called coelurosaurs," Currie says. "Velociraptor is also one of these, as are all the ostrich-mimic dinosaurs that keep getting confused with baby tyrannosaurs.The interesting thing is that tyrannosaurs are actually more closely related to these dinosaurs than they are to massive carnivores like Allosaurus."
Tyrannosaurs used to be lumped with other giants into a group called carnosaurs, Currie adds, "but recently there's been a lot of work showing that tyrannosaurs are actually just big versions of coelurosaurs." Despite their size, tyrannosaurs share a lot of birdlike features with the smaller dinos.
These tiny Chinese dinosaurs lived 50 million years or so before tyrannosaurs made the scene. So if they had feathers, and modern birds have feathers, it's quite possible that tyrannosaurs, falling on a family-tree branch somewhere in between the other two groups, had them as well. "There's a very good chance that all of these things, at least in some stage of their lives, had feathers on their bodies," Currie says.
And if tyrannosaurs ran around in packs, Currie argues, the likelihood they had feathers is even greater. "With packs you get social behavior. And with social behavior you have things like courtship or threat displays, and the use of display structures like feathers," he says. It's pretty clear that's what Caudipteryx, with a peacocklike fan spreading out from its tail, was doing; those feathers are the wrong shape and in the wrong place to have anything to do with flight.--J. F.
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Bone Puzzles
Identifying random dinosaur bones pulled from the earth is both an art and a science. Having a whole skeleton, especially a skull, makes things a lot simpler. But that's rare, since a carcass is often scattered before it fossilizes. When Barnum Brown ventured to the Alberta badlands in 1910 and discovered a mound of leg bones, vertebrae, and a few teeth--but no complete skulls--he concluded the skeletal remains were from both tyrannosaurs and ornithomimids, or ostrich mimics. Brown shipped the fossils home and never took a closer look.
Phil Currie opened the jumbled drawers of bones 86 years later and lined up all the right legs on a table. In another cabinet, he found leg bones that were known to be ostrich mimics'. A baby tyrannosaur leg is virtually identical to that of an adult ornithomimid. It's about the same size, and since the two dinosaurs were probably closely related, the angles and positions of the leg bones are also very similar. But when Currie looked more closely at the two, he realized that even though the bones Brown found were the right length to belong to ornithomimids, they were all too wide to be anything but those of young tyrannosaurs. "The babies of large animals sort of anticipate how much mass they're going to have to support when they get big," Currie explains. "A baby elephant bone may be the same length as an adult deer bone, but it will be more massive."
Then Currie noticed that the walls of one of the broken leg bones were also too thick to belong to an ostrich mimic, which has relatively thin bone walls, as birds do today. And every animal has a somewhat different pattern of muscle attachment to bones. By carefully comparing the scars from where the muscles were on Brown's finds with those on the ostrich mimics, Currie could see enough differences to assure him that he was looking at a set of fossils that were exclusively tyrannosaurs. --Fenella Saunders
