If Hollywood is planning any more sequels to “Jurassic Park” or “The Flintstones,” it may have to seriously revise how it portrays the biggest and most familiar of all dinosaurs: the sauropods. Those are the classic long-necked, long-tailed plant-eaters seemingly tall enough to reach and chew off treetops.
The big beasts may have been long, according to an article by local researchers in Friday’s edition of the research journal Science, but they were physically unable to raise their necks very high.
That would mean not only Hollywood, but a lot of the best museum dinosaur displays in the world–including the Field Museum’s magnificent skeleton of a 90-foot brachiosaurus that soars across the north end of its main hall–are inaccurately displayed. In a world of rapidly evolving science, especially dinosaur science, new knowledge often quickly renders museum displays obsolete.
“What we’re proposing,” said Northern Illinois University paleontologist Michael Parrish, a co-author of the article, “is very different from the popular image of these animals with their heads craned high up in the air, feeding on the tops of the trees. . . . (W)e’re seeing (sauropods) with the necks held horizontally, or even curved downward a lot of the time, while feeding on water plants, ferns or low shrubs.”
Parrish and his co-author, University of Oregon computer scientist Kent Stevens, used special software designed by Stevens to make three-dimensional computer models from actual skeletons of two different sauropod species, an apatosaurus (pronounced ah-PAT-oh-sawr-us) and a diplodocus (dih-PLOD-o-cus). The almost complete skeletons are in the Carnegie Museum of Natural History in Pittsburgh.
The computer models allowed the researchers to see the biomechanics of the dinosaurs’ neck vertebrae, the way they interacted when the neck moved in different positions.
When viewed that way, Parrish said, it is apparent that there is no way sauropods could have arched their necks upward, as popularly depicted. The vertebral bones in their necks are shaped in a way that they would collide when the necks were arched, making such elevation impossible.
For years, scientists have puzzled over how sauropods could pump sufficient amounts of blood from their hearts to brains elevated so high above the body. Some researchers have suggested that they probably had multiple hearts to do the job.
If they couldn’t raise their heads high, as Parrish suggests, then there would have been no problem of getting blood to the brain.
“From a botanical context,” Parrish said, “it makes sense as well that they didn’t raise their heads very high. So far as we know, virtually the only plants that grew very high when these animals were around–the late Jurassic period–were conifer trees.
“We don’t think the huge herbivores would be going after needles as a food source, because there isn’t much nutrition there.”
Parrish compared sauropods to vacuum cleaners, with the big herbivores like the cannister style as opposed to uprights. Cannister vacuums have long necks that sweep across the floor without the main body having to move much; with uprights, the entire unit moves in order to cover the areas being cleaned.
“These guys had teeth that looked like pencil shafts, with no facets for tearing or chewing,” Parrish said, “so we believe they were pulling leafy matter off plants that was actually broken down in some sort of gizzard in their insides, like birds.
“There apparently were a lot of rivers in this (western United States) area when they were around, and this ability to sweep over large areas with their necks would have been advantageous in reaching plants on the margin of riverbanks or lakeshores.
“Fossil footprint evidence of these species found in this area also seem to parallel edges of bodies of water.”
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First discovered about a century ago, sauropods were thought to be so heavy and ungainly that scientists for decades believed they lived in water to support their weight.
More recently, evidence suggests they were strictly land-based. They were the biggest land animals ever to have lived, reaching perhaps 100 feet in length or more.
Perhaps based on observation of giraffes, which by virtue of height and long necks have exclusive grazing rights to treetops, scientists assumed the long necks of sauropods were used for tree-grazing too.
But giraffes are poor analogs to sauropods, Parrish said, because giraffes are so different anatomically and biologically from dinosaurs,
He and Stevens decided to combine skills to study sauropod necks several summers ago when Stevens was a student in a class Parrish teaches on dinosaurs for college professors. They agreed to do so, Parrish said, as they stood under an apatosaurus skeleton, discussing how the mechanics of its movements might have worked.
“That sounds reasonable to me,” said William Hammer of Parrish and Stevens’ theory of sauropods’ neck movement. Hammer, an Augustana College paleontologist, found and is restoring the first dinosaur bones discovered in Antarctica.
“The idea used to be that these things ate off the tops of trees and could even stand on their hind legs, like the brachiosaurus in the `Jurassic Park’ movie. But there’s a lot of people who disagree with that now.
“Instead of conjecture, (Parrish and Stevens) are looking at the biomechanics of a dinosaur, putting together all the physical parameters known about them into a computer and seeing how the bones fit together and how all the components interact.”
Parrish said he and Stevens have presented their findings in one form or another at several recent scientific meetings, getting generally favorable responses. With their data now more widely available in the Science article, it will undergo the normal rigors of scientific inquiry, exposed to critical evaluation by other researchers.
If Parrish and Stevens’ theory becomes generally accepted, it will mean the Field Museum, where Parrish also holds a position as research associate, is displaying its brachiosaurus skeleton inaccurately.
The Field brachiosaurus bones were the first of the species ever found, discovered by Field paleontologist Elmer Riggs in 1900. It is one of the Chicago museum’s prized artifacts, and the reconstructed skeleton’s head proudly sits atop the graceful, swanlike upward curve of its neck three stories over the floor of the display.
“Kent (Stevens) and I were in the Field together recently, looking over the brachiosuarus skeleton,” Parrish said. “We decided that if it were posed in a more natural posture, the neck would be straight out and its head would be bashing into the upper gallery.”
The Field, like all natural history museums, has to deal regularly with erroneous displays based on outdated information, said William Simpson, a paleontologist and curator there.
Simpson currently is working to mount Sue, the museum’s spectacular Tyrannosaurus rex skeleton.
“Not too many years ago,” Simpson said, “T. rex and all bipedal (two-legged) dinosaur carnivores were shown in a classic, tripodal pose as their most natural posture. They stood almost upright on two legs and the tail as the third leg of the tripod.
“With information we now have, we pose T. rex as a `T,’ with the head straight out in front as a more efficient weapon, and its tail straight out in back. The theory is they were hunters and wouldn’t have dragged their tails along the ground.”