70-Million-Year-Old Moves
In the swampy lowlands of primordial Wyoming, an allosaurus springs open-mouthed from ambush.
The 1.4-ton predator slams its snout into its startled prey with pile-driver force. The impact drives its serrated upper jaw like a steak knife deep into muscle and sinew. Yanking back its head, the carnivore carves off broad ribbons of flesh. Then the allosaurus backs away to wait at a safe distance for its prey to bleed to death.
No one has any direct evidence of how the most common carnivore of the ancient American West attacked its prey, but a computerized engineering analysis of its intricate skull at Cambridge University in England is yielding provocative clues to its hunting habits--insights at odds with traditional ideas about how this prehistoric predator behaved.
By bringing fossils like the allosaurus to life in the virtual reality of a computer hard drive, researchers are overturning years of misconceptions about how dinosaurs moved and behaved when they were the living lords of creation.
In recent months, the computerized work has allowed researchers to discover the importance of smell to Tyrannosaurus rex, hear the low-pitched mating call of a dinosaur dead for 75 million years and rebuild the skeleton of a 70-million-year-old triceratops.
The advances come from the increased use by paleontologists of computer modeling techniques, high-resolution X-ray imaging machines, three-dimensional laser scanners, stereo lithography, electron microscopes and sophisticated engineering software.
For the first time, these devices are revealing glimpses of the long-vanished brains that animated these mammoth beasts and the hearts that sustained them. The machines allow scientists to examine anatomical details hidden by the minerals and stone that encrust each fossil, providing new ways to gauge dinosaur bone structure and growth patterns.
“It is an exciting time because we have these new tools,” said Gregory M. Erickson, an expert on paleobiology at Florida State University. “We are getting bombarded with pretty incredible advances.”
With supercomputers on loan from nuclear weapon laboratories and analytical software adapted from structural engineering, researchers are studying the biomechanics of dinosaur skeletons to better understand how they moved and ate.
Borrowing high-resolution imaging techniques developed for hospital radiology departments and the aerospace industry, paleontologists also are learning to dissect dinosaur fossils digitally. Computerized X-ray tomography allows them to see inside fossils to reveal previously unknown details of brain and bone structure without actually having to risk damaging delicate specimens.
Entire fossil collections are being X-rayed, converted to digital archives and made available online.
“The whole idea is to get 3-D images of our bones into a computer where we can model them, to see how things walk or how tails work, to analyze them in either a mechanical or biological way,” said dinosaur expert Jack Horner at the Museum of the Rockies in Bozeman, Mont., whose laboratory helped pioneer the application of these techniques to dinosaur bones. “Paleontologists are realizing that we can apply some pretty sophisticated tools to fossils and get cool results.”
Until recently, however, many of these techniques were prohibitively expensive for perennially underfunded paleontologists. Engineering programs can cost $15,000. Precision CAT scanning can run $100 an hour. Stereolithographic models can average about $3,000 each. Depending on its complexity, a resin prototype of a single 4-inch bone can cost as much as $1,000; an entire dinosaur skeleton, $200,000.
But, as with most computer technologies, the price has declined steadily. And for paleontologists who have found the money to use them, the new techniques are proving their worth, researchers said. In recent months:
* Scientists from the Field Museum in Chicago used computerized X-ray tomography to make a three-dimensional digital model of the 2,000-pound skull of the largest T. rex ever discovered. The creature’s olfactory bulbs, twin structures devoted to detecting odors, were almost as large as its brain, leading researchers to conclude the 7-ton meat-eater followed its nose to track prey. Ohio State University researchers also are using CAT scans to probe fossilized nostrils of long-necked sauropods, duckbill hadrosaurs and horned triceratops.
* Researchers at the New Mexico Museum of Natural History and the Sandia National Laboratories used a hospital CT scanner and a supercomputer to build a three-dimensional working model of the convoluted air passages inside the crest of a swamp-dwelling dinosaur called parasaurolophus. The low-pitched rumble resounding in the chambers of the 4-foot-long skull suggested the creature may have used its resonant crest as a natural amplifier to sound its presence.
* Computer scientist Kent A. Stevens at the University of Oregon developed precise modeling software called Dinomorph to analyze the biomechanics of dinosaur skeletons. Digital reconstruction of skeletons of 50-ton sauropods like apatosaurus and diplodocus showed him that these 100-foot-long creatures could not lift their necks high enough to forage among the treetops, as often portrayed in films and museum exhibits. Instead, they browsed along the ground.
* Ralph Chapman and his colleagues at the Smithsonian Museum of Natural History scanned and digitized 133 triceratops bones from dozens of angles to create a three-dimensional digital dinosaur that took up nearly 50 gigabytes of computer storage. Computer modeling allowed the Smithsonian scientists to assess each joint in the skeleton, reconstruct the new posture and then animate it to see how it all moved together, providing more accurate information about the gait and posture of one of the last dinosaurs to roam Earth.
“We let the animal rebuild itself,” Chapman said.
Stevens at the University of Oregon said the computer tools allow researchers to experiment with the fit and arrangement of bones that under normal circumstances are too heavy to lift or too fragile to handle. “You have to put the whole animal together and come up with a design that makes sense. The only way to solve these things is to make digital models.”
To reconstruct the bite-and-slash attack of the carnivorous allosaurus, paleontologist Emily Rayfield at Cambridge University and her colleagues at the Museum of the Rockies in Montana made digital X-ray images of a 150-million-year-old fossil skull, then converted the images into a virtual skull that contained 250,000 elements.
Using a computerized engineering technique called finite element analysis, she tested how this lattice of bones responded to the biomechanical forces generated by the chewing and biting of its 80 teeth, just as an engineer might use computer-aided design software to evaluate how bridge trusses or skyscraper girders behave under mechanical stress.
The allosaurus skull revealed a bite no stronger than a contemporary wolf or leopard and barely a quarter the strength of an alligator. Its bite was six times weaker than that of a T. rex.
In contrast, the front of the animal’s skull was unusually strong, able to withstand a loading of six metric tons--26 times the maximum force exerted by its clenched teeth.
“You have an animal with a weak bite and a very strong skull,” said Rayfield. “It was very unusual.”
This led them to conceive a hunting strategy that took advantage of the odd combination. The best thing about such engineering programs, Rayfield said, is that they allow researchers to test their ideas in a more objective way.
“Before,” she said, “it was one person’s opinion against another’s, especially where feeding strategies and other behavioral things were concerned.”
