Pterygotus is one of the largest known eurypterid, or sea scorpion and one of the largest arthropods of all time. It lived from the Early Silurian to Devonian period. Pterygotus could reach a length of 2.3 metres (7 ft 7 in). It was an accomplished swimmer and could move with speed and agility through the water and would swim by flapping its long, flat tail up and down.
It was one of the top predators in the Paleozoic seas and lived in shallow coastal areas, hunting fish, trilobites and other animals using stealth.