(suborder Odontoceti, superfamily Delphinoidea)
A family comprising Monodon monoceros (narwhal) and Delphinapterus leucas (beluga, or white whale), whales in which the forehead is high and rounded, there is no dorsal fin, the flippers are rounded and short, and the tail fin is notched at the posterior margin. The beluga has 8–10 teeth in each jaw. The narwhal has two teeth. In the male, one (almost always the left) and rarely both of these may grow forward into a spiral tusk up to 2.5 m long. Narwhals are grey with black mottling, adult belugas white or near-white. Adults of both species grow to a length of about 6 m. Their diet consists of demersal and pelagic fish, and Crustacea. They are distributed throughout Arctic waters and enter the larger rivers within the Arctic Circle.
Subjects: Zoology and Animal Sciences.