Identity Crisis: Dolphin or Porpoise? What is the difference between a dolphin and a porpoise! "Dolphin" usually refers to the specific group of small, toothed cetaceans in the family Delphinidae. There are over 30 species of true dolphins, including familiar species like the bottlenose, spinner, and spotted dolphins. Although the largest members of this group are commonly called whales because of their size, they are actually most closely related to other dolphins. The large dolphins include killer whales and pilot whales."Porpoise" refers to six species in the family Phocoenidae. All porpoises are relatively small by cetacean standards, measuring 7 feet (2 meters) or less as adults.
The notable differences between dolphins and porpoises are these:
Dolphins Porpoises Always have cone-shaped teeth Always have spade-shaped teeth Usually have a beak Never have a beak Usually have a hooked or curved dorsal fin (some have no dorsal fin) Usually have a dorsal fin shaped like a triangle (some have no dorsal fin) Heyning, John E. Masters of the Ocean Realm: Whales, Dolphins, and Porpoises. (Seattle: University of Washington Press, 1995), p. 31.
Hence your pic of a "whale" tossing a porpoise is really two dolphins. Interesting.
Oh, so the orca (killer whale) is actually a dolphin. I am fascinated by cetaceans, and other marine mammals, and love to learn about them.
Still, as Big Look says, there is much about them that remains mystery.