The rex sole, Glyptocephalus zachirus, is a flatfish of the family Pleuronectidae. Locally, it may also be known as a witch or threadfin sole (due to the filamentous pelvic fin on the eyed surface). It is a demersal fish that lives in temperate waters on sand or mud bottoms at depths of up to 900 metres (3,000 ft), though it is most commonly found between 61 and 500 metres (200 and 1,640 ft). Its native habitat is the northern Pacific, from Baja California in Mexico up the coasts of the United States, British Columbia and Alaska, across the Bering Sea to the coast of Russia and the Sea of Japan. It is slow-growing, reaching up to 60 centimetres (24 in) in length (though its average length is 36 centimetres (14 in)), and it can weigh up to 2.0 kilograms (4.4 lb). Maximum reported lifespan is 24 years.