The Best Fossil Finds Are Often Those Where Only A Bit Of Bone Sticks

ABOVE THE SURFACE. IN THOSE CASES MOST OF THE BONE IS STILL SHELTERED FROM EROSION. THAT'S HOW IT WAS WITH KATHY WANK EL'S T. REX.

during the long dry spells. When it shrinks it cracks all over, making the ground into a layer of cracked crust over dust, stuff we call "popcorn." You can just imagine what the popcorn cracking does to bones. If a T. rex died and was fossilized in bentonite, it could end up in a million pieces.

Yet another reason it's so hard to find a dead T. rex is that there probably weren't that many live ones. T. rex was a meat eater, and fossils of meat eaters are always a lot harder to come by than those of the animals they ate. That's because there are always a lot more plant eaters. Think about the African savannah today. For every pride of lions, wildebeests roam in the tens and hundreds of thousands. The same probably was true for dinosaur predators. It would help explain why 85 percent of all dinosaur carnivores are known from five or fewer specimens. And nearly half the species of meat-eating dinosaurs have only one specimen to their name.

T. rex has been such a familiar, popular animal for so long that it's difficult to believe that we hardly know it. But the truth is, we're lucky to have any proof of it at all.

In the space of two months, the two most complete T. rexes ever found were unearthed (ours and "Sue" in South Dakota). That's luck. But getting a T. rex out of the ground takes skill, and still more luck.

We have more electrical equipment than the early dinosaur diggers had, from littie air hammers to big pneumatic drills and backhoes. Dave Gillette, the Utah state paleontologist, has been experimenting with remote sensing equipment to find dinosaurs by sound waves, magnets, and infrared rays. For a long time dinosaur bones have been detected with Geiger counters, since many fossils are "hot" with uranium.

But mostly we dig dinosaurs exactly the same way as the early dinosaur diggers in the American West did one hundred years ago. We still use picks and shovels to get down to the bone layer, still wrap the bones in burlap and plaster, still brace them with wood, and still haul them out to the laboratory for cleaning.

We go more slowly, though, than the early collectors. They were spurred on by competition among the big eastern museums like Yale University's Peabody Museumof Natural History, the Carnegie Museum of Natural History, and the American Museum of Natural History, all of which wanted lots of stuff to display in the museum right away. So the prospectors used dynamite to blow the tops of hills, risking the fossils. They stole fossils and shot at each other. And whatever they found that looked big enough to display, they'd bring back to the museum. There several preparators would clean the fossil up quickly, and a scientist would write a short paper describing it as a dinosaur and invent a name for it. Then they'd put it together on steel rods, stick it out on the display floor, and go look for more.

Nowadays we're trying to answer several biological questions when we dig up dinosaurs. We do take things like this T. rex back to the museum, and a cast of it will make a great showpiece. But we're also trying to learn something about the animal. So we dig up T. rex more slowly. We take notes about the kind of sediment it is in. We map it to see how the bones lie in the ground, so that we can try to figure out the circumstances of its death and burial. We sift through all the dirt and rock around the bones, in the field and in the lab, looking for other dinosaur bones, mammal and reptile fossils, fossil leaves, and pollen spores—anything that will tell us what kind of environment this animal lived in. And died in.

The study of what happened to animals after they died and how they were buried is called taphonomy. A German scientist pioneered it back in the 1920s, and Peter Dodson of the University of Pennsylvania was the first to apply it systematically to dinosaurs, twenty years ago. He studied the way dinosaur bones in Dinosaur Provincial Park in Alberta, Canada, got moved around by ancient stream channels.

It's very difficult to tell for sure how an animal died because you very rarely find it preserved just as it looked in the moment of death. That's true even for a

ABOVE: THIS IS ONE OF THE MOST REMARKABLE OF ALL FOSSIL FINDS. FROM THE STATE MUSEUM IN ULAN BATAAR. MONGOLIA, SHOWING A CARNIVORE, VELOCIRAPTOR,

0 0

Post a comment