Giant sea scorpion fossil discovered

One of its claws might feed an entire family, but this sea creature would be more likely to eat the family.

British researchers said Tuesday that they had discovered a foot-and-a-half-long fossilized claw of an ancient sea scorpion, a species that would have been 8 feet long, making it the largest arthropod ever discovered.

“We knew the sea scorpions were among the largest creepy-crawlies ever, but we didn’t realize just how big they could get,” said paleontologist Simon J. Braddy of the University of Bristol, the primary author of the report in the journal Biology Letters. The fossil was found in a quarry near Prum, Germany.

Sea scorpions became extinct about 250 million years ago, but they were precursors of modern land-based scorpions. Smaller varieties are common in the fossil record, and evidence suggests that they ventured forth onto land for at least brief forays.

But “there is no way this thing could have crawled out onto land,” Braddy said.

“This is simply too spindly. Its legs would break under its own weight.”

And what does an 8-foot sea scorpion eat? Pretty much anything it wants to, Braddy said. The creature would have been the dominant predator in its environment, feasting on armored fish, early vertebrates, other varieties of arthropods and even on smaller sea scorpions.

The lack of predation may have been one factor that allowed the scorpions and other ancient species to grow so large, he said. The high oxygen content of the atmosphere then – 35% compared with 21% today – also probably was a factor.

But the sea scorpions were doomed. When vertebrates evolved to large sizes, “the tables were turned,” Braddy said.

“The only way they could cope was by downsizing and hiding away. That’s why all of them today are very small.”

 thomas.maugh@latimes.com