Eurypterids, often called "sea scorpions," are an extinct group of marine arthropods that lived from the Ordovician to the Permian periods, approximately 485 to 250 million years ago. They are closely related to modern horseshoe crabs and arachnids, featuring a segmented body, large pincers, and a long tail spine. Some species grew to impressive sizes, with the largest reaching over 2.5 meters (8 feet) in length. These creatures inhabited various environments, from shallow coastal waters to deeper oceanic regions. Eurypterids were predatory, feeding on fish and other marine organisms. Their fossils have been found worldwide, providing valuable insights into ancient ecosystems and the evolution of arthropods.