Buried Treasure

Schweitzer made yet another surprising discovery in her cache of T. rex bones. "I started pulling the fragments out of the box and I said, 'Oh my gosh, we have a girl and she's pregnant'." She had encountered what is known as medullary bone, which is characteristic of ovulating birds. The calcium to make eggshells comes from the bones, which form new tissue with a distinctive configuration. "This tissue told me dinosaurs are related to birds not just morphologically"--in structures such as the pelvis and feathers--"but physiologically. In their reproductive physiology, they are birds."

Other researchers have been doing equally remarkable things with bones. Kent Stevens, a computer scientist at the University of Oregon, became interested in the large long-necked sauropods of the late Jurassic Period, about 150 million years ago. Members of this family, which includes apatosaurus and diplodocus, were assumed to be treetop browsers, usually depicted standing foursquare with their heads high above the ground, like fat, short-legged giraffes. Every morning, in fact, Nate Murphy sees one on the Sinclair Oil sign across the road from his research station. But when Stevens modeled the bones on his computer, he discovered the vertebrae just don't seem designed to fit together that way. Instead, their natural position seems to lie almost parallel to the ground, or even below the horizontal, where the animal could browse on low shrubs or aquatic plants. This has been an unwelcome revelation to many laymen, Stevens has found. "They don't meet people's childhood expectations; you're replacing it with something that doesn't look as majestic--a lot of people have trouble with that," he says. Nor has it necessarily endeared him to museum curators, who will have to remount their specimens. As for Sinclair Oil Co., which began using the apatosaurus symbol in 1932, Stevens's research hasn't come up. "We have no plans to change our logo," a spokesman told NEWSWEEK.

Stevens's next project involves the biomechanics of T. rex, a much more dynamic and interesting animal; he's intrigued by the question of how a five-ton biped could squat down--to eat a carcass, say--and how it got back up again. On a related topic, John Hutchinson of the University of London has been looking at how fast T. rex could travel, a topic of continuing fascination for anyone who has ever had a nightmare about trying to outrun one. Fifty years ago the science-fiction writer Ray Bradbury envisioned a T. rex covering "one hundred yards in six seconds," which is 34 miles an hour; in "Jurassic Park," a T. rex almost catches a Jeep in fourth gear. But the filmmakers confided to Hutchinson that they couldn't plausibly model a T. rex traveling at those speeds. Given the animal's dimensions and its inferred stride, its legs would have to spin like a cartoon character running off a cliff. Examined frame by frame, the movie dinosaur's speed is a bit more than 15 miles an hour. Hutchinson thinks that's probably about right; he calculates a top speed in the range of 10 to 25 miles an hour, with the upper end much less likely than the lower. A land animal's speed is limited by the amount of muscle it can pack into its legs, but there is a point of diminishing returns beyond which the added muscle costs more in weight than it contributes in force. To run at 45 miles an hour, Hutchinson has written, T. rex would need to have 86 percent of its body weight in its leg muscles, an obvious absurdity. Recently he cut that estimate by more than half, to 41 percent, which he considers still "quite unlikely considering its anatomy."

Hutchinson's work would appear to have implications for the other great T. rex debate: was it a top-of-the-food-chain predator or primarily a scavenger? Hutchinson himself has no desire to cast doubt on the tryannosaurs' ferocity, which is a good way to pick a fight at a meeting of paleontologists. The big prey animals of its era wouldn't have run very fast either, he says, adding that "you don't have to go 45 miles an hour to catch an animal running at 15." On the other side, Horner points out that it doesn't matter how slow you walked if the animal you're eating is already dead. Most researchers assume that, like alpha predators today, T. rex would have eaten whatever it could get its jaws around. Gregory Erickson of Florida State University has calculated the growth rate of T. rex, based on analyzing growth rings (analogous to tree rings) in their bones, and concluded that during their adolescent growth spurt they would have gained an average of nearly five pounds a day. "It's hard to imagine there was that much carrion lying around," muses the American Museum's Norell.

The question was a major theme of a T. rex conference held earlier this month at the Black Hills Museum, where John Happ of Shenandoah University showed a triceratops skull collected near Jordan, Mont., with about a third of its left horn missing and apparently bitten off. Tooth marks on the animal's neck frill were the right distance apart to have been made by a tyrannosaur, which was the only large carnivore known from that place and time. By itself that doesn't disprove the scavenger hypothesis, but the wounds on the triceratops skull had started to heal, which meant it was alive and healthy enough to have fought back when T. rex attacked. The position of the bite marks indicates that the two animals were face to face in their struggle. "We don't know what happened next, but triceratops did survive," Happ says. "It still had two big horns remaining. It may be that T. rex did a cost-benefit analysis and abandoned the fight. These animals lived for millions of years, so they must not have been in the habit of making bad decisions."

They lived for millions of years, but they were perilously close to extinction; the climate may have already been changing, for reasons still being debated; the meteorite that would end the Cretaceous Period with a bang was spinning through space on its way toward its fateful impact with Earth. And all were awaiting the evolution of an unimaginable creature that would someday calculate the trajectory of comets, and dig up the long-buried bones to probe their secrets--and marvel at the intricacy and beauty of it all.