SCIENCE

Davis, whose findings appear online in the May 19 issue of Science Express, said this most likely makes the ice sheet the only large terrestrial ice body in the world to be gaining mass.

"Many recent studies have focused on coastal ice sheet losses and their contributions to sea level rise," Davis said in an interview Friday. "We think that the East Antarctic ice sheet is probably gaining mass at a rate comparable to the amount of mass being lost by the Greenland ice sheet."

Increased precipitation, especially snowfall, accounts for the sheet's growth, Davis said. Other scientists have predicted that global warming would have that effect in some regions, but Davis cautioned that it is too early to tell whether global warming is causing the growth of East Antarctica's ice.

-- Juliet Eilperin

How a Stegosaur Used Its Plates

Everybody knows that stegosaurs were the pea-headed dinosaurs with the double row of bony plates growing like banana leaves down their backs. But what, exactly, were the plates for?

To find out, a team led by researchers at the University of California at Berkeley cut up some of the plates, called scutes, and compared them with similar bones on related species.

The team concluded that stegosaurs used the scutes to identify other stegosaurs, probably a wise strategy for a not-particularly-bright vegetarian sharing its world 175 million years ago with ferocious predators.

"There were four possibilities for the scutes," said team member Russell Main, a Harvard biologist. "They could be for defense, display [to attract mates], thermoregulation or species identification."

In the spring issue of the journal Paleobiology, the team concludes that the scutes were too lightweight for defense.

Display was also ruled out, because male and female stegosaurs "look the same."

Thermoregulation -- controlling body temperature -- seemed a plausible explanation, because scute surfaces were threaded with blood vessels that could have cooled the blood during warm weather and warmed it during cool weather. But many stegosaur ancestors had scutes that lay flat or rose only slightly, not a good arrangement for heat exchange.

The team concluded that the vessels probably carried blood to facilitate rapid scute growth, like the vessels in the antlers of elk or moose. Although the scutes "may have acted passively" as thermoregulators, Main added, their most likely purpose was species recognition.

-- Guy Gugliotta