Rare sea scorpion - horseshoe crab - Silurian Limulus elasmopods The width of the specimen is 16-22mm, and the surrounding rock is 35-40mm. Origin Ukraine Location - Velykozalissya, Kamianets-Podilsky District, Khmelnytsky Region Era - Late (upper) Silurian Regional Stratigraphy—Ludlow Stage, Ustya Formation The horseshoe crab is an important type of arthropod that lived in the Paleozoic era and is a close relative of modern arachnids. Because of its scorpion-like shape, it is commonly known as sea scorpion. This fossil preserves the head in remarkably complete detail Notes on purchase: There are several different shapes in the picture, and the final details of the product received shall prevail.