Homing in on the longest animal.

Homing in on the longest animal

Paleontologists have started using a shotgun in the hunt for a gargantuan dinosaur dubbed Seismosaurus. The gun is part of an arsenal of sophisticated techniques scientists are now attempting to apply to paleontology.

For years, geophysicists have used remote sensing devices to locate petroleum reserves, mineral ores and other valuable deposits underground. More recently, remote sensing has helped uncover archaeological structures. But this is the first time paleontologists have used it in an attempt to locate fossils.

Seismosaurus, or "earth-shaker," is an unofficial name used to describe the huge, 140-million-year-old skeleton that David D. Gillette and his colleagues have been excavating from the desert of central New Mexico since 1985 (SN: 8/13/86, p. 103). In shape, the bones resemble those from the well-known diplodocid dinosaurs but are 10 percent to 80 percent larger. The dinosaur's dimensions indicate it once reached a length of at least 120 feet, and possibly more than 140 feet, making Seismosaurus the longest animal known in Earth's history, says Gillette, who works out of Salt Lake City as Utah's state paleontolist. Other paleontologists are excavating another huge Utah diplodocid, unofficially called Supersaurus, which may also have stretched beyond 120 feet in length (SN:4/29/89, p.261).

Since 1987, scientists from Los Alamos (N.M.) National Laboratory have conducted remote sensing tests at the Seismosaurus fossil site. Using ground-penetrating radar, magnetometers and radiation-sensing devices, they have tried to locate bones beneath about 8 feet of sandstone.

Other scientists are testing a different approach at the site. Their technique, called seismic tomography, resembles medical CAT scanning. Using a modified shotgun, the researchers send a blast of vibrations through the ground and record the diffracted vibrations with a string of receivers in a nearby borehole, says Alan J. Whitten from Oak Ridge (Tenn.) National Laboratory. Through several different shots along a line, Witten and his colleagues can produce an image of buried objects that may be bones. Their technique proved successful last summer when excavations uncovered two huge Seismosaurus vertebrae in spots identified by the tomography.

Witten says he will next test the tomographic equipment by trying to locate shallow coal seams. The equipment was originally designed to track the underground spread of hazardous waste, he says.