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Now we Know: 350-Million-Year-Old Sea Scorpion Breathed Air

Colorful CT scan of a sea scorpion
James Lamsdell

Sea scorpions lived around 300-400 million years ago, could grow to the terrifying dimension of eight feet long, had strong barbed claws with which they could hold prey while they likely sawed into it with a large jagged tail. Now we know something else about them: they could breathe air.

Paleobiology Ponderings

While you might spend your days wondering where you might vacation, or what you could make for dinner, there are some scientists out there who put their time to use pondering the breathing habits of ancient arthropods. James Lamsdell, who heads a paleobiology lab at West Virginia University, is one such man.

For about 20 years, he had been wondering how a 340-million-year-old sea scorpion was able to thrive in aquatic environments while also breathing on land. The creature, also known as a eurypterid, was originally from France and had been stored in a museum in Glasgow for the last 30 years. Previous research had shown that it mostly lived in the water, but that it did, occasionally, travel on land. The eurypterid’s nearest living cousin is the horseshoe crab, which goes on land to lay its eggs but can’t breathe while doing so. So the Glasgow specimen puzzled Lamsdell, and he decided to run the fossil through a CT scan.

Collapse-Proof Gills

The most noticeable find was that the plates that formed creature’s gills were connected by pillars known as trabeculae, which are found in modern air-breathing spiders and scorpions.

“That props the gills apart, so they don’t collapse when out of water,” Lamsdell said. “It’s something that modern arachnids still have. Finding that was the final indication. The reason we think they were coming onto land was to move between pools of water. They could also lay eggs in more sheltered, safer environments and migrate back into the open water.”

In their analysis, Lamsdell and his team also noticed that the sea scorpion had back legs shaped like paddles and front legs that were equipped with spikes, which, they believe, helped the animal grind up its prey once captured. He hopes to continue unearthing qualities of the eurypterid.

“One of the things that would be really cool to do is to flesh out this model and try to reconstruct exactly how the legs could move and how they were positioned,” he said, “like reconstructing the fossil as a living animal.”

The finding has been published in the peer-reviewed journal, Current Biology.