Earliest sea scorpion discovered in Iowa

Huge predator stalked ocean 460 million years ago

illustration of giant sea scorpion

SEA MONSTER  A new species of giant sea scorpion (illustrated) lived about 460 million years ago and may have used paddlelike limbs to swim.

Patrick Lynch/Yale Univ.

Giant scorpions may have terrorized the seas some 460 million years ago.

The species of sea scorpion, Pentecopterus decorahensis, stretched up to 1.7 meters long — almost as long as a twin-sized bed. Scientists unearthed more than 150 fragmentary remnants from the sandy shale of an impact crater in what is now Iowa.

The sea predator may have used its forelimbs to capture prey and its paddlelike hind limbs to swim or dig, Yale University paleobiologist James Lamsdell and colleagues report September 1 in BMC Evolutionary Biology. Pressed between layers of rock for hundreds of millions of years, the specimens lay so well preserved that researchers could make out very fine hairs bristling from the scorpion’s underside.

Pentecopterus is the earliest sea scorpion yet discovered, edging out the previous record holder by some 9 million years. 

FOSSIL LIMB A newly discovered giant sea scorpion had some serrated limbs (shown) peppered with bristles. J. Lamsdell

Meghan Rosen is a staff writer who reports on the life sciences for Science News. She earned a Ph.D. in biochemistry and molecular biology with an emphasis in biotechnology from the University of California, Davis, and later graduated from the science communication program at UC Santa Cruz.

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