Pterygotus is an extinct eurypterid, related to arachnids and commonly called as the famous sea scorpions. It lived in the Silurian and Devonian periods.

Fossils have been found in North America, South America, Europe and Australia. It is related to the larger eurypterid Jaekelopterus, which also lived during the Silurian and Devonian. It is similar to the freshwater creature Slimonia.

Pterygotus could reach a body length of 16 meters long.^[1] It had a pair of large compound eyes. It also had another pair of smaller eyes in the center of its head. It had 4 pairs of walking legs. A fifth pair of legs were swimming paddles. It also had a pair of large pincers.