About 460 million years ago, a sea scorpion about the size of an adult human swam around in the prehistoric waters that covered modern-day Iowa, likely dining on bivalves and squishy eel-like creatures, a new study finds.
The ancient sea scorpions are eurypterids, a type of arthropod that is closely related to modern arachnids and horseshoe crabs. The findings — which include at least 20 specimens — are the oldest eurypterid fossils on record by about 9 million years, said study lead researcher James Lamsdell, a postdoctoral associate of paleontology at Yale University.
The findings are also the largest known eurypterids from the Ordovician period, which began approximately 488 million years ago and ended 443.7 million years ago. The sea creatures measured up to 5.6 feet (1.7 meters) long.
Researchers dubbed the newfound species Pentecopterus decorahensis, named for Greek warships (penteconter) and the Greek word for wings (pterus) because the sea scorpion was likely a top predator that sped through the water, the researchers said. The species name also honors the Iowa city of Decorah, where the fossils were uncovered.
“The best way to describe this animal is bizarre,” Lamsdell told Live Science. “For a long time, I had trouble being sure that this was one species because there are so many strange things about it.”