water, but which is capable of forays onto land for short periods of time.

The researchers named the new scorpion Parioscorpio venator. The genus name means "progenitor scorpion," and the species name means "hunter." They outlined their findings in a study published today in the journal Scientific Reports.

"We're looking at the oldest known scorpion—the oldest known member of the arachnid lineage, which has been one of the most successful land-going creatures in all of Earth history," said Loren Babcock, an author of the study and a professor of earth sciences at The Ohio State University.

"And beyond that, what is of even greater significance is that we've identified a mechanism by which animals made that critical transition from a marine habitat to a terrestrial habitat. It provides a model forother kinds of animals that have made that transition including, potentially, vertebrate animals. It's a groundbreaking discovery."

The "hunter scorpion" fossils were unearthed in 1985 from a site in Wisconsin that was once a small pool at the base of an island cliff face. They had remained unstudied in a museum at the University of Wisconsin for more than 30 years when one of Babcock's doctoral students, Andrew Wendruff—now an adjunct professor at Otterbein University in Westerville—decided to examine the fossils in detail.

Wendruff and Babcock knew almost immediately that the fossils were scorpions. But, initially, they were not sure how close these fossils were to the roots of arachnid evolutionary history. The earliest known scorpion to that point had been found in Scotland and dated to about 434 million