Prehistoric two-metre scorpion wasn’t so ferocious after all (Wired UK)

Ryan Somma / CC BY-SA 2.0

An enormous long-extinct sea scorpion that roamed Paleozoic
shorelines has had its top predator status revoked following a
closer look at its eyes and claws.

The giant
pterygotid eurypterid
 is not just the largest scorpion
that ever lived, but the largest of any arthropod — a
classification that includes all insects, centipedes, arachnids and

The two-metre-long scorpion roamed shallow basins for 35 million
years — seven times longer than humanity has been present on
Earth. Fossil evidence of its massive, grasping claws and
forward-facing compound eyes led scientists to think that it was a
fearsome predator.

But a new analysis of those eyes suggests that it might not have
been as dangerous as previously thought. “We thought it was this
large, swimming predator that dominated Paleozoic seas,” said Ross
Anderson, a Yale graduate student and lead author of the paper. “But one thing it would need to be able to find the
prey, is to see it.”

Anderson rigged up a mathematical analysis model to understand
the sea scorpions’ eyes — using a scanning electron microscope on
the fossils to measure the properties of the thousands of eye
lenses without damaging them. The results were compared with other
extinct sea scorpions and their modern-day equivalents, such as the
horseshoe crab. “We measured the angle between the lenses of the
eye itself,” Anderson said. “The smaller the angle, the better the

It turns out that the species couldn’t see as well as other
eurypterids, and probably made its home in dark or cloudy water. As
such, it’s more likely that it preyed on soft-bodied, slower-moving

“Maybe this thing was not a big predator, after all,” Anderson
said. “It’s possible it was more of a scavenger that hunted at
night. It forces us to think about these ecosystems in a very
different way.”

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