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 known for their large size, with some species reaching over 2.5 meters (8 feet) in length. Eurypterids had a segmented body, a pair of large pincers, and multiple legs, which made them effective predators in ancient oceans. These creatures are closely related to modern horseshoe crabs and arachnids, such as spiders and scorpions. Fossils of eurypterids have been found in various locations worldwide, providing valuable insights into prehistoric marine ecosystems. Their unique adaptations allowed them to thrive in diverse environments, including shallow coastal waters and deep-sea habitats.