Greenland sharks are part of the dogfish shark order, which holds many shark records: the oldest, the smallest, the longest pregnancies, and the shark that has the biggest estimated population in the world. Moreover, members of the dogfish order range in size from the smallest shark of all, the dwarf lanternshark, to one of the largest in the world, the Greenland shark.
These sharks have many physical characteristics in common. For example, they all have two dorsal fins, five sets of gills, and mouths underneath their snouts. Greenland sharks are closely related to the Pacific sleeper shark.
They also have differences: The dogfish group includes a slow, stout 20-footer; a few sharks that glow in the dark; and the aptly named cookiecutter shark that takes cookie-shaped bites from its prey.
In total, there are 120 species in the dogfish order. These dogfish sharks are found all over the world, from warm and tropical seas to cold arctic waters, shallow and deep. Dogfish sharks earned their name because many of them hunt and travel in large packs—similar to dogs.