SCIENCE

This recent image of the Crab Nebula is the largest ever taken by the Hubble Space Telescope and the most detailed view of one of astronomy's most studied objects, assembled from 24 exposures.
This recent image of the Crab Nebula is the largest ever taken by the Hubble Space Telescope and the most detailed view of one of astronomy's most studied objects, assembled from 24 exposures. (Nasa, Esa And Jeff Hester Of Arizona State University)
Monday, December 5, 2005

On the Trail of a Giant Scorpion

About 330 million years ago, for questionable reasons, a water scorpion the size of a small human lurched out of the lake where it lived and lumbered slowly across the sand, dragging its tail behind.

Paleontologist Martin A. Whyte recently found the creature's tracks imprinted in a stretch of sandstone in Scotland. The trail includes the prints of six feet flanking the groove cut by the tail. Whyte estimates that the scorpion was about 5 feet, 3 inches long and about 3 1/2 feet wide.

"It is certainly moving very slowly," Whyte said from his University of Sheffield office, in England. "It was moving with a jerky movement, and its tail wasn't buoyed up in any way."

Although fossilized shells of giant water scorpions were first found in Scotland in 1831, Whyte said his find, reported last week in the journal Nature, is the first evidence of this creature making a land journey.

Chances are it was not a good idea, Whyte acknowledged, because a walking scorpion had no means of fending off enemies. "I hadn't thought of that," Whyte said. "Maybe it was just going from one body of water to another."

Dry land also offered few dining options for a beast that used comblike limbs near its mouth to sift river bottoms for edible sea creatures. Such a mechanism would be next to useless on the beach.

Nevertheless, Whyte said the scorpion track suggests that these six-legged arthropods were making the same transition to land that four-legged, salamander-like reptiles made at the same time. The water scorpions "would never have succeeded" out of water, he said.

And they did not, going extinct about 280 million years ago.

-- Guy Gugliotta

Gold Rush Mercury Still in Bay

San Francisco Bay is still struggling to clear up the mercury contamination gold miners left 150 years ago, a new report by U.S. and Canadian researchers finds.


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