Mesoplodon stejnegeri

The teeth are in the center of the lip line, and the dark forehead is gently sloping.

A pair of teeth protrudes from the center of the lip line, a dark forehead with a gentle slope, a black, dark gray or brown back, and may have white oval scars on the sides of the body. The small dorsal fin is almost triangular or hooked, with a slightly concave rear edge, a well-developed dorsal ridge extending from the dorsal fin to the caudal fin, a long beak, a distinctly curved lip line, small pectoral fins, a light-colored or scarred abdomen, a spindle-shaped body, and some scars on the body.
Females and calves have no protruding teeth and may be difficult to distinguish from other beaked whales. Adult males are unique in that they have two large, laterally flattened teeth about 20 cm from the front of the lower jaw, and a very curved lip line; some of the two teeth bend toward each other and cut into the upper "lip". The juvenile has a distinct light-colored neck stripe. Although the white cap on the head of Hart's beaked whale is a distinct feature, it can sti

Many of the earlier records were later identified as other species of the genus Mesobacterium, so there is some confusion about the range. The main source of information is from strandings, but experienced whale watchers have reported several from Alaska, especially the Aleutian Islands (apparently the center of the range). Although sometimes called Bering Sea beaked whales, they seem to inhabit only the deep waters of the southern end of the Bering Sea; shallower waters further north may be less common. There are also small but distinct populations in the Sea of ​​Japan, especially off the coasts of Honshu and southern Hokkaido. Prefers deep waters beyond the continental shelf.