At first glance, it’s hard to tell a porpoise and a dolphin apart from one another. Both are fascinating undersea creatures, both are carnivores, and both belong to the same scientific group: Cetacea. However, there are slight physical differences between the two: Porpoises tend to be smaller than dolphins and do not have pronounced beaks. Dolphins have cone-shaped teeth, while porpoises have spadeshaped teeth. Dolphins usually have a hooked or curved dorsal fin, and porpoises usually have a triangle-shaped dorsal fin. (Some have no dorsal fin at all.) There are over 30 species of true dolphins, including familiar species like the bottlenose, spinner, and spotted dolphins.