Living World / Dinosaurs

Bite marks revealed in a computed tomography (CT) scan of the skull of Sue, the world's most complete Tyrannosaurus rex, may be love chomps, says paleopathologist Bruce Rothschild.

The barosaur at the entrance hall of the American Museum of Natural History in New York—rearing up on its stout hind legs, its fire-hose neck curling up two stories in fury—is the signature icon for the institution and maybe even for the city itself. It is also a big, bone-faced lie.

"It's a great entrance animal and a great posture for stimulating interest," Bruce Rothschild whispers to me. "But there is no way the animal stood like that."

An energetic man dressed in catalog chinos and a plain dress shirt, its tail mostly out, Rothschild is a descendant of the famous European banking and wine dynasty, and this morning he has flown his private plane in from Pennsylvania to take me on his own tour of the dinosaurs. A medical doctor (of human patients), Rothschild is often sought out these days by paleontologists for his observations about the diseases revealed in bones (the dinosaur kind)—and the subsequent deductions about how these long-extinct creatures might have lived. Thanks to Rothschild, the once obscure field of paleopathology is now bringing a fresh sense of realism to our understanding of ancient life.

"If the animal stood up like that," Rothschild says, "you'd expect to see the same stress fractures that you'd find in a ballet dancer. Stress fractures in the bones of the forefeet. They didn't call them thunder lizards for nothing! Stress fractures should also occur in the lumbar region below the ribs. But they aren't there."

As he looks at the dinosaur's lower back, Rothschild points to his own lumbar region; in his view, the differences between himself, a barosaur, and a ballet dancer are practically marginal. We are all creatures, living and dying, pounding the ground, eating, catching diseases, and recovering from them. The bones of people and dinosaurs endure the history of our actions and allow the acute observer to find, long after our deaths, clues to how our lives were lived.

Amid a crowd of parents piloting strollers through laughing teenagers on school trips, Rothschild pushes toward the rail to make his case against the upright barosaur. "People in the past talked about cardiac requirements for such an action, but the thing that always bothered me was the absence of evidence." Rothschild is Sherlockian by temperament, and like the famous detective in "Silver Blaze," he has found the dog that didn't bark. Still, his discovery—the absence of stress fractures—is good only for disproving the old theory. If the barosaur couldn't rear up on its hind legs, how did it defend itself?

"The ability to whip his tail has been raised," Rothschild says. From the intonation in his voice, it's clear that he is not buying this theory either. "There's a claw in the forefoot," he adds tentatively, then turns silent when he realizes that he is about to plunge straight into an untested theory of his own. Later, he lets it slip out: "The barosaur could have just squatted. That would have gotten his neck out of the way of predators and created a space to wield his front claw."

No modern creature squats defensively, so this is a fairly radical assertion to make about an animal that has been dead for 150 million years. Still, if there is anyone justified in making such assertions, it is Rothschild. In fact, there is some evidence to back up his idea: At least one sauropod fossil displays an injury suggesting that it was attacked by a predator while crouched in a squatting position. "I think the evidence that these dinosaurs squatted is being written up now," he says before adding modestly, "I'm involved."

In the sideline world of paleopathology, Rothschild is a star, the coauthor of some 600 papers. In outward appearance, however, he is your average rheumatologist, with one practice at the Arthritis Center in Lawrence, Kansas, and another at the Arthritis Center of Northeast Ohio, in Youngstown. His life took a turn toward the nonaverage in the early 1980s, when a colleague innocently asked him to examine a fossil of a diseased marine lizard to identify what ailed it—something he regularly does for his living Homo sapiens patients—and Rothschild got hooked. Since then, he has become the go-to guy for anyone trying to identify a deposit or scar on a bone fossil that might suggest an ancient ailment. Once a week or so, Rothschild fields a call or an e-mail from another part of the world asking him to interpret a relic bone that exhibits some kind of intriguing anomaly.