As of 2015, scientists disagree on an exact count due to differences in classification, but most sources agree there are over 30 different species of dolphin. Most of the species recorded belong to the group, Delphinidae.
Dolphins consist of a large group of marine species and a smaller group of river-going species. Some scientists consider porpoises a kind of dolphin, while others class them separately. This is one reason why there is disagreement over the number of dolphin species.
Zoologists count 32 to 36 species in the main group, Delphinidae. This group contains all the familiar marine dolphins, as well as some creatures usually thought of as whales, such as the orca. The river dolphins contain either five or seven species, depending on how they are classified, while the porpoises contain seven species in total.