Smithsonian Magazine has an article about some very old scorpions.  Scientific Reports has a paper describing some scorpions that lived about 437 million years ago, during the Silurian Period.  These animals, called Parioscorpio venator, lived in what is now modern day Wisconsin.  Their fossils were discovered back in the 1980s.  When they were alive, Wisconsin was an extensive reef system.  Trilobites would have lived along side Parioscopio.

Half a billion years ago, the continents were quiet. Earth’s animals—represented largely by shelled mollusks, armored arthropods, and a smattering of wriggly, jawless fish—breathed with gills, not lungs, and hunted their prey at sea.

But sometime, possibly during the Silurian (the geologic period spanning 443 million to 416 million years ago) an intrepid creature, likely equipped with sturdy limbs and a set of gas-cycling tubes that could leech oxygen from air, decided to crawl ashore. In habitually venturing out of the ocean, this animal paved a habitat-hopping path for countless lineages of land-dwellers to come—including the one that eventually led to us.

The identity of this pioneering terrestrial trekker has long perplexed paleontologists. Over the years, several candidates have come forth, all known only by their fossilized remains. Two of the most promising possibilities include many-legged millipedes, eager to snack on the predecessors of today’s plants, and stinger-tipped scorpions—one of the world’s oldest arachnids, the group that also includes spiders. But when and how these arthropods first made that crucial transition from water to land remains an unsolved puzzle.