Dolphins are mammals that evolved from land to sea, adapting to vastly different aquatic environments. They primarily feed on fish, possess dorsal fins and pointed snouts, and are widely distributed. Did you know that besides the well-known marine dolphins, there are also rare freshwater dolphins? This article will introduce you to 20 species of dolphins, including those from five major families: Pontoporiidae, Platanistidae, Iniidae, Lipotidae, and Delphinidae.
Main classifications of dolphins
The only surviving species in the family Pontoporiidae is the silver dolphin (Pontoporia blainvillei), commonly known as the "La Plata dolphin," which inhabits the La Plata River in Argentina and the adjacent Atlantic coast in South America. It measures 1.3-1.7 meters in length, with a brown body and grey belly. The snout accounts for 15% of its body length, and it has a broad dorsal fin. It is endangered due to being caught in fishing nets.
The Platanistidae family is solely represented by the Ganges finless porpoise (Platanista gangetica), which includes two subspecies, the Ganges and the Indus, both of which are endangered. They have long snouts, narrow mouths, and vestigial, aphakic eyes, relying on echolocation for navigation.
The family Iniidae includes freshwater and estuarine dolphins. A representative species is the Amazon pink dolphin (Inia geoffrensis), which lacks a dorsal fin, measures 1.8-2.5 meters in length, and can skillfully maneuver its head to hunt. It is currently listed as an endangered species.
The family Lipotidae is now extinct, containing only the Yangtze finless porpoise (Lipotes vexillifer), commonly known as the baiji dolphin. This species is functionally extinct due to the development and pollution of the Yangtze River.
The Delphinidae family is the most well-known family of marine dolphins. They are small to medium-sized and commonly found on shallow continental shelves. Distinguishing features include a pointed dorsal fin, a prominent forehead (sonar organ), and are typically gray to bluish-gray in color. They are gregarious hunters with sharp teeth.
Examples of well-known types
Common dolphin (Delphinus delphis): Widely distributed, with bright side body coloration, and is well protected.
Antarctic dolphin (Cephalorhynchus commersonii): white body, short snout, extremely agile.
Striped dolphin (Stenella coeruleoalba): Common in the Mediterranean, with distinct stripes.
There are many other well-known species such as the bottlenose dolphin, Ross dolphin, and Fraser dolphin.
