In taxonomy, Pyrodictium is a genus of the Pyrodictiaceae. It is a genus of submarine hyperthermophilic archaea whose optimal growth temperature ranges is 80 to 105 °C. They have a unique cell structure involving a network of cannulae and flat, disk-shaped cells. Pyrodictium are found in the porous walls of deep-sea vents where the temperatures inside get as high as 400 °C, while the outside marine environment is typically 3 °C. Pyrodictium is apparently able to adapt morphologically to this type of hot–cold habitat.