* Dolphins belong to the family Delphinidae, which includes over 40 different species.
* Porpoises belong to the family Phocoenidae, which includes only six species.
The confusion arises from their similar appearance and behavior:
* Both have a streamlined body shape, a dorsal fin, and flippers.
* Both are highly intelligent and social animals.
* Both can be found in various ocean regions.
However, there are several key differences:
* Size and shape: Dolphins are generally larger than porpoises and have more slender bodies.
* Dorsal fin: Dolphins typically have a curved or hooked dorsal fin, while porpoises have a triangular or pointed fin.
* Snout: Dolphins have elongated beaks or snouts, while porpoises have blunt or rounded snouts.
* Teeth: Dolphins have conical teeth, while porpoises have spade-shaped teeth.
Historically, the term "porpoise" was used more broadly to refer to any small, toothed whale. However, as scientists gained a better understanding of marine mammals, the terms "dolphin" and "porpoise" became more specific.
In summary:
* Dolphins and porpoises are separate families of marine mammals.
* The term "porpoise" was historically used more broadly but has become more specific to refer to the Phocoenidae family.
* The confusion arises from their similar appearance and behavior, but they have distinct physical characteristics.
Therefore, the term "porpoise" did not become used for dolphins. Instead, it was used more broadly historically and then became narrowed down to its current specific meaning.