Scorpions are among the oldest arachnids known. They date to the Silurian, but most of them were probably aquatic at that time. They had gills rather than lungs, and Silurian scorpions have been found in Great Britain and New York – which, you must remember, were not really very far apart during the Silurian.
This 2008 paper has some great photos of fossil scorpions from the Silurian – showing pretty clearly that they haven’t changed much in more than 400 million years.
—Richard I. Gibson
Illustration from Extinct Animals by Sir Edwin Ray Lankester (1905, public domain)