Size estimates range from 4 to 9 meters based on extrapolation from skull measurements. A Japanese specimen was 6.5 meters in length, which seems about average based on partial skeletal specimens. Like all beaked whales, this species has a prominent slender beak. Also diagnostic of beaked whales, the throat has two grooves which form a V shape and the fluke is not notched. This whale has a proportionately smaller head than most beaked whales. It is, however, larger overall than most of its close relatives. Longman’s beaked whales are most morphologically similar to Baird’s beaked whales (Beradius bairdii). They may be distinguished, however, because Longman’s beaked whales have a blow hole with concavity oriented forward, toward the anterior of the whale. In Baird’s whales the blow hole tilts toward the posterior. The dorsal fin is larger than that of most beaked whales. The lower jaw contains only a pair of oval teeth, which do not protrude from the jaw. The skin coloration varies between brown and bluish gray and tends to lighten around the flank and head. These whales are sexually dimorphic, with males tending to be larger. Weight estimates could not be found.
Range length: 4 to 9 m.
Sexual Dimorphism: male larger