MORGANTOWN, W.Va. – A new study conducted by a West Virginia University geologist suggests that the largely aquatic extinct arthropods known as sea scorpions were able to breathe air on land.
The 340 million-year-old sea scorpion, or eurypterid, originally from France have been preserved at a Glasgow, Scotland museum for the last 30 years. After an assistant professor of geology in the Eberly College of Arts and Sciences, James Lamsdell, read about these “strange specimen” 25 years ago, while conducting his doctoral studies, he decided to dig into this case study.
While existing research suggested it would occasionally go on land, there was nothing known on whether these eurypterids could breathe air. The closest living relative to the eurypterid is the horseshoe crab, which lays eggs on land but is not able to breathe above water.
These details puzzled Lamsdell for several years, until he decided to reach out to a colleague. He asked Victoria McCoy, at the University of Wisconsin-Milwaukee, for a CT scanner.
We wondered if we could apply new technology to look further into what was preserved of this specimen. I like the science and detective work that goes into research. And this was a cold case where we knew there was potential evidence.”James Lamsdell, assistant Geology professor at WVU
Through computed tomography (CT) imaging, researchers were able to study the respiratory organs of the three-dimensional eurypterid. This lead to two findings that stood out to Lamsdell.
Lamsdell noticed that each gill on the sea scorpion was composed of a series of plates, but the back contained fewer plates than the front. This prompted the question of how the eurypterid could breathe.
That’s when they found pillars that connected the different plates of the gill, which are seen in modern scorpions and spiders, according to Lamsdell. These pillars, or small beams of tissue, are called trabeculae.
“That props the gills apart so they don’t collapse when out of water,” Lamsdell explained. “It’s something that modern arachnids still have. Finding that was the final indication.”
Lamsdell believes the reason they were coming onto land was to move between pools of water. The eurypterid could also lay eggs in more sheltered, safer environments and then migrate back into the open water.
Lamsdell was able to finally crack the case that was living in his head for more than 20-years. However, he isn’t done studying this fossil, just yet. He believes there’s more to unearth.
Lamsdell noted that the sea scorpion’s back legs expand into a paddle shape, which he suspects would have been used to swim. He added that the bases of their legs also had spikes that ground up food for them, that they had maneuvered into their mouths.
“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,” Lamsdell said, “like reconstructing the fossil as a living animal.”
Lamsdell and McCoy conducted this research with co-authors Opal Perron-Feller of Oberlin College and Melanie Hopkins of the American Museum of Natural History. Their research was published on Current Biology.