Indus river dolphin in the context of "Ganges River dolphin"

Platanistidae is a family of river dolphins containing the extant Ganges river dolphin and Indus river dolphin (both in the genus Platanista) but also extinct relatives from freshwater and marine deposits in the Neogene.

The Amazon river dolphin, baiji, and La Plata dolphin were once thought to belong to Platanistidae (e.g. Simpson, 1945), but cladistic and DNA studies beginning in the 1990s showed that the former three taxa are more closely related to Delphinoidea than to the South Asian river dolphin. The extinct odontocete families Allodelphinidae and Squalodelphinidae are closely related to Platanistidae. Fossils from this clade have been found in deposits in North and South America, Europe, and Central Asia.

South Asian river dolphins are toothed whales in the genus Platanista, which inhabit the waterways of the Indian subcontinent. They were historically considered to be one species (P. gangetica) with the Ganges river dolphin and the Indus river dolphin being subspecies (P. g. gangetica and P. g. minor respectively). Genetic and morphological evidence led to their being described as separate species in 2021. The Ganges and Indus river dolphins are estimated to have diverged 550,000 years ago. They are the only living members of the family Platanistidae and the superfamily Platanistoidea. Fossils of ancient relatives date to the late Oligocene.

South Asian river dolphins are small but stocky cetaceans with long snouts or rostra, broad flippers, and small dorsal fins. They have several unusual features. Living in murky river waters, they have eyes that are tiny and lensless; the dolphins rely instead on echolocation for navigation. The skull has large crests over the melon, which help direct their echolocation signals. These dolphins prey mainly on fish and shrimp and hunt them throughout the water column. They are active through the day and are sighted in small groups. Both species are listed as endangered by the IUCN Red List of mammals. Major threats include dams, barrages, fishing nets, and both chemical and acoustic pollution.