Photos of baleen whale dorsal fins can be used for photo-identification. Their narrow elongated upper jaw bones arch upwards to house extremely long baleen. The lower jawline is deeply curved upwards in profile. Encrusting growths, called callosities, on the head, jaws, and blowhole areas of right whales are yellow-white. Accumulations of natural markings such as these aid researchers in photo-identification studies.
Rorquals have a broad, flat rostrum and a slightly curved jawline.
Humpback whales have several knobs on their heads. Gray whales have a narrow head with a slight curve to the jawline. The neck vertebrae are unfused in rorquals and gray whales, which allows for some flexibility at the head and neck. Blowholes are covered by muscular flaps. These flaps provide a water-tight seal.