Image 2 of 2: Long-beaked common dolphins mating. The male is underneath the female and swimming with her upside down. These 2 images captured the male with his mouth open and many teeth showing.
Delphinus capensis mating mouth open teeth 2015 08-10 SB Channel-050
We see surface lunge feeding humpback whales, one with its mouth open. The inside of the mouth shows the upper jaw, pink soft palate, and tan baleen surrounding the rim.
Megaptera novaeangliae surface lunge feeding groups 2015 06-25 SB Channel-050