The Greenland shark, (Somniosus microcephalus) also known as the gurry shark or grey shark, is a large shark of the family Somniosidae, closely related to the Pacific and southern sleeper sharks. This large, heavy-set shark grows to an average 8-14 feet long but can get to be 24 feet. It has a short, rounded snout, small eyes, and relatively small dorsal fins. Although it is an apex predator, it is a slow swimmer, and likely ambushes its prey and scavenges for carrion. The largest fish in the Arctic Ocean—and the only shark found there year-round—the Greenland shark also inhabits the North Atlantic and Russian high Arctic. Infrequently observed at the surface, it can live in waters 7,200 feet deep and between 28.4 to 44.6 Fahrenheit (minus 2 to 7 degrees Celsius). The Greenland shark consumes capelin, char, halibut, herring, lumpfish and salmon among other fishes. It also feeds upon marine mammals such as seals, sea lions and cetaceans. It swims at 1.22 km/h (0.76 mph), with its fastest cruising speed only reaching 2.6 km/h (1.6 mph). Because this top speed is a fraction of that of a typical seal in their diet, biologists are uncertain how the sharks are able to prey on the seals. There are no known natural predators of the mature Greenland shark, which is most likely due to its massive size. Greenland sharks are born alive (a process known as ovoviviparity) after an estimated gestation period of 8–18 years. About ten pups per litter is normal, each initially measuring some 38–42 cm (15–16+1⁄2 in) in length. Within a Greenland shark's uterus, villi serve a key function in supplying oxygen to embryos. Greenland sharks have a life expectancy of at least 272 years and could reach 392, give or take about 120 years. What's more, these slow-growing creatures don't reach reproductive age until around 150 years old. The oldest Greenland Shark found is estimated to be around 400 years old.