Monday, June 20, 2005

ENV: Dinosaurs in situ

From the upcoming issue of Newsweek

Buried Treasure
With the help of new fossil discoveries and new technologies, scientists are learning how dinosaurs lived—and died.
By Jerry Adler, Newsweek

June 27 issue - Seventy-seven million years ago—nearing the end of the age of dinosaurs, although they still had 12 million years to go—a young duck-billed hadrosaur lay down to die just over the horizon from the vast inland sea that covered much of central North America.

Dinosaurs did not ordinarily rest easy in death: they were torn apart by scavengers or washed downstream in a flood, and their bones were scattered and lost, at least until people arrived to dig them up. Many of the skeletons in museums today are made up of bones that never stood together in life. But this dinosaur met a different fate. Lying on its side in a shallow river, the carcass was quickly buried in a fine-grained sediment that preserved not just the shape of the bones, but impressions of the skin and flesh, and a tantalizing suggestion of organs within. When he first laid eyes on it, in a small museum in north-central Montana, the famous dinosaur researcher Robert Bakker whipped off his hat and fell to his knees, and tears welled up in his eyes. "It was," he says, "like seeing the Pieta."

You don't have to share Bakker's passion for dinosaurs to appreciate this unique animal, whose photo appears for the first time in this issue of NEWSWEEK (below). Barely emerging from the rock, lying with its head bent back as if held by the current against a stream bank, it evokes, far better than any mounted skeleton, a real animal that lived and died. Four years after the freelance paleontologist Nate Murphy dug it out of a Montana hillside, he is still pondering how to study the insides of an animal that has turned to rock without destroying it in the process. "I'm not sure what we're going to find," he muses. "Did it have a crop in there to help it digest plants? We might be able to see the heart. Was it three-chambered [like a modern reptile], or four-chambered like a bird? Wouldn't it be great to know that?"

Even to imagine looking inside an intact dinosaur amounts to a revolution in paleontology, a field in which entire life histories are routinely inferred from a tooth. Another revolution is already underway: skeletons that have stood mutely for years are yielding their secrets to researchers armed with CT scans and supercomputers and sheer ingenuity. A biologist dissolves the mineral matrix in a dinosaur bone, and finds, amazingly, evidence of blood vessels and even corpuscles. The speed of Tyrannosaurus, long a topic of fervent guesswork, is now being calculated by the algorithms of biomechanics. Engineers have radically revised our view of how the giant long-necked sauropods stood and walked. Dinosaur dioramas in museums are sprouting feathers—unsuspected just a decade ago—as evidence accumulates for the close relationship of dinosaurs with birds. These discoveries are explored in a new exhibit at the American Museum of Natural History in New York, the first major dinosaur exhibit there in five years. Over the past 20 years, says Mark Norell, the museum's head of paleontology, his field has left its roots in taxonomy to traffic in speculation on dinosaur physiology, ecology and even behavior. It is, he says, a branch of science no longer driven just by discoveries, but by research and experiment.

Yet discoveries haven't slowed down, either; Earth still hides secrets from its past, and the turn of every season uncovers new skeletons as the land erodes around them. New kinds of dinosaurs are described every month. Peter Makovicky, curator of dinosaurs at the Field Museum in Chicago, estimates there are 900 valid genuses, at least double the figure from two decades ago. (Many, of course, are known only by skulls, or even parts of skulls; as Bakker has found, even with a creature as big as five-ton triceratops, "usually you don't get much of the body, because someone chomped on the body.") Farmers in the Chinese province of Liaoning are uncovering, in a series of exquisitely preserved fossils, evidence of an entire ecosystem of plants, insects, fish, turtles, small mammals and birdlike dinosaurs never seen before. The Dilong paradoxus, a five-foot-long early relative of Tyrannosaurus,with rudimentary feathers evidently meant for warmth, not flying. Or Microraptor gui, whose feathered hind limbs must have given it the appearance of a four-winged bird. In the badlands of Patagonia and in the American West, the cycle of soil deposition, uplift and erosion has come full circle since the Late Cretaceous, exposing sediments that last saw the light 70 million years ago. In these places, dinosaur bones are lying out on the ground, just waiting to be picked up by someone who can tell them from rocks. (One test is to lick it; bone sticks to the tongue.) Two years ago brothers Steve and Patrick Saulsbury from Sioux City, Iowa—a physician and a veterinarian—were out with their friend Brian Buckmeier—a lawyer—looking for fossils in the rugged hills of western South Dakota. They spotted a bony knob the size of a quarter at the base of a hill, and 30 feet higher up, a couple of blackened teeth. They were attached to the skull of a pachycephalosaur, one of a group of horse-size dinosaurs distinguished by an impressive array of knobs, spikes and crests surrounding their bulging foreheads. But, unlike every other specimen known from North America, this one had a flat, rather than domed, forehead. "The flatheads are known from earlier periods in China and Mongolia," says Bakker, "but around 80 million years ago they evolved domes, and that's all we've found in North America. Until this one, which dates from right before dinosaurs were about to go extinct. I've written about how dinosaurs were slowing down, not budding off new species. I was wrong."

It's hard to imagine a lawyer in his spare time making a discovery in, say, molecular genetics, but dinosaur paleontology remains closer in spirit to the scientific world of Darwin than of Crick and Watson. Big universities compete with regional institutions like the Black Hills Museum of Natural History in South Dakota and the Museum of the Rockies in Montana. The Saulsburys donated their pachy skull to the Children's Museum of Indianapolis. Academic credentials are optional; Nate Murphy learned about dinosaurs from his grandmother, the noted paleontologist Nelda Wright, but he doesn't even have a college degree. To fund his studies he established a research center in a former tire shop in the remote town of Malta, Mont., staffed largely by volunteers and supported by a trickle of tourists and by adventure-seekers who pay him for the privilege of tramping the countryside in search of the next T. rex. A wealthy New York dinosaur enthusiast named Coleman Burke personally underwrote Murphy's fossil-collecting trip to Patagonia last year. Dinosaurs lack a strong funding constituency in the corporate world, except for Universal Studios and Steven Spielberg, who established a "Jurassic Park Institute" to recycle some of their brontosaurian profits into grants for fieldwork. Creationists, who think dinosaurs died in the Flood, have their own issues with paleontology, as did a Brooklyn rabbi who wrote Norell to complain that if word got out that birds were really dinosaurs, people might decide that chickens weren't kosher.

It was on a fossil-hunting trip in the summer of 2000 that one of Murphy's volunteers spotted a bone poking out of a low west-facing bluff in the remote reaches of a cattle ranch north of Malta. Murphy's chief assistant—his teenage son, Matt—dug down just far enough to uncover four tail vertebrae, and called over his father. Nate, an easygoing, unflappable scientist perpetually clad in khaki shorts and a bush hat, compensates for a lack of formal training with a remarkable gift for visualizing how bones fit together to make an animal. Looking up at the bluff, he spotted what to him was unmistakably the outline of a pelvis and an ankle. The next day he shared his discovery with the rancher on whose land it was found.

"I tried to look excited," the landowner, Howie Hammond, recalls. "When I got home my daughter asked what it looked like. I said, 'Like a big stain in the rock'."

The first order of business was to bestow a name. Not a scientific name; it was a well-known species, Brachylophosaurus, a Late-Cretaceous duck-billed herbivore that grew as long as 35 feet. But individual specimens are traditionally given cute nicknames by their discoverers. A psychologist might speculate that this is to compensate for human puniness in the face of these terrifying creatures. The spectacular T. rex at the Field Museum in Chicago is known as Sue. (It was discovered by Sue Hendrickson.) The three other almost intact duck-bills Murphy has found are named Elvis, Peanut and Roberta. This one was dubbed Leonardo, after a piece of graffito on a nearby rock: Leonard Webb loves Geneva Jordan 1916.

The following summer Murphy returned to excavate the fossil, carefully blasting off 18 inches of cap rock, removing seven feet of loose sand and rock with a grader before bringing in volunteers to remove the last four feet by hand. As they worked on a forelimb, a volunteer saw something unusual and called to Murphy.

"I took one look and said, 'Oh, my God, this is skin'."

When he realized he was dealing with more than a skeleton, Murphy had to revise his plan; instead of digging out the bones one by one, he had his team dig around the 23-foot-long specimen, so it could be moved to his research lab in one six-ton chunk. He had arranged to borrow an Air Force helicopter to airlift the specimen out of its remote valley, but on the day it was supposed to happen—September 11, 2001—the Air Force had other priorities, so it was carefully winched aboard a flatbed truck. Countless hours of work since then have gone into removing, a grain at a time, the matrix of sedimentary rock in which Leonardo remains half embedded. The process has uncovered the spiny crest along the animal's back and the network of tendons that moved its tail; the fine-grained scales on the back and flanks, and the coarser ones on the lower legs, where tough twigs and shrubs would have brushed it. Two places on the torso where the surface was inadvertently cracked offer a glimpse of what's inside, displaying what Murphy believes are the fossilized remains of intestinal contents. For Karen Chin, an expert on dinosaur coprolites—fossilized dung—at the University of Colorado, this is a potential mother lode of droppings that hadn't hit the ground yet; she's been studying the material in hopes of determining what Leonardo was eating. A paleobotanist has detected 36 different kinds of pollen in the material. Murphy's next goal is to transport Leonardo to Hill Air Force Base in Utah, which has one of the world's largest CT scanners. There the heart, lung, kidneys and other organs, if they are indeed preserved inside, can be visualized and even modeled in three dimensions. He estimates it will cost close to a million dollars. This is less than a Las Vegas casino has already offered to pay to exhibit Leonardo, but Murphy and the Hammonds aren't selling; dinosaur tourism has the potential to be an important part of the economy of this thinly populated region.

A CT scan of an entire dinosaur mummy would be an astonishing achievement, but no more so, perhaps, than what Mary H. Schweitzer, a biologist at North Carolina State University, accomplished with a mere fragment of T. rex bone. This was from a specimen unearthed in 2003 by John R. Horner of the Museum of the Rockies. "He had to break it to get it back to camp," she says. "It was too big to get in the helicopter." Schweitzer put the fossil in a weak acid, which is how biologists study fresh bone; the acid dissolves the mineral matrix, leaving organic tissue behind. If no one had tried it before with a fossil, it was because he had no reason to expect that any organic matter would be left after millions of years. To Schweitzer's amazement, she recovered a flexible substance that resembled collagen, the major organic component of bone, plus evidence of blood vessels and traces of red blood cells. The blood cells, moreover, appear to have nuclei, holding out the possibility of recovering genetic material. Finding even fragments of DNA after 68 million years would be a surprise, but some researchers think it's possible. Leaving aside the unlikely possibility of cloning an entire animal, it would be a potential bonanza to researchers attempting to reconstruct the relationships among dinosaurs, birds and reptiles. "If we're ever going to find dinosaur DNA," she muses, "it will be in samples like this."

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.

With Mary Carmichael


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