for National Geographic News
If you think scorpions are scary, try this on for size: a six-legged water scorpion the size of a human. Newly discovered tracks reveal that about 330 million years ago, just such a creature lumbered along the riverbanks in present-day Scotland.
The fossilized track is the largest of its kind ever found and shows these now extinct creatures could walk on land, according to Martin Whyte, a geologist at the University of Sheffield in England.
"There's been lot of debate about this particular [species of] water scorpionwhether it could only live in water or if it could come out. What the track shows is they could come out at least for short intervals," he said.
The geologist describes the find in tomorrow's issue of the science journal Nature.
Blair Hedges, an evolutionary biologist at Pennsylvania State University in University Park, agreed that the tracks looks like they were made on solid ground.
"That tell us that about this time our ancestors, the first vertebrates with four limbs instead of fins, were confronting very large arthropods on land," he said. "That's the neat thing it brings up."
The footprints were made by a species of Hibbertopterus, a family of water scorpions that are among the largest arthropodsa group that includes insects and crustaceansever known.
Whyte estimates the individual who made the track was 5.2 feet (1.6 meters) long and 3.2 feet (1 meter) wide.
The track itself is 20 feet (6 meters) long and about 3 feet (1 meter) wide.
"It's huge, absolutely giant," Hedges said. "To consider an arthropod made the thing, that's really impressive. A lot of people don't realize the arthropods of that time period, including dragonflies, millipedes, and centipedes, were much larger than today."
Whyte's analysis of the tracks suggests that the ancient water scorpion took its sweet time as it lumbered along the shoreline.
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