How to Tell a Dolphin From a Porpoise: Look at the Teeth

People often use the words dolphin and porpoise as if they meant the same animal. NOAA’s National Ocean Service explains how to tell them apart. It comes down to faces, fins and figures. Dolphins tend to have prominent, elongated beaks and cone-shaped teeth, while porpoises have smaller mouths and spade-shaped teeth. A dolphin’s dorsal fin, the one in the middle of the back, is hooked or curved, while a porpoise’s is triangular. Generally, dolphin bodies are leaner and porpoises’ are portly. Dolphins are also far more common. According to NOAA, most scientists agree there are 32 dolphin species, plus five closely related species of river dolphin, and only six porpoise species. One famous animal belongs firmly with the dolphins: the orca, or killer whale, is the largest member of the dolphin family.