Somniosus microcephalus, commonly known as the Greenland shark, is a large species of shark found in the cold waters of the North Atlantic and Arctic Oceans. It is known for its slow growth rate and long lifespan, with some individuals estimated to live over 400 years, making it one of the longest-living vertebrates. This shark typically reaches lengths of 2.5 to 4.5 meters (8 to 15 feet) and has a distinctive, stout body with a small head. Somniosus microcephalus primarily feeds on fish, including cod and herring, as well as carrion, and is known for its unique ability to thrive in deep, dark waters.