River Dolphin - Taxonomy

Taxonomy

The four families of river dolphins are classified by Rice, 1998 as belonging to the superfamily Platanistoidea. Formerly, Platanistidae was listed as the only extant family of the Platanistoidea superfamily. The previously accepted classification treated all four families as belonging to this family and treated the Ganges and Indus River dolphins as separate species.

Five lineages of dolphin have evolved to live in big, muddy rivers. River dolphins are thought to have relictual distributions. Their ancestors originally occupied marine habitats, but were then displaced from these habitats by modern dolphin lineages. Many of the morphological similarities and adaptations to freshwater habitats arose due to convergent evolution, thus the superfamily Platanistoidea is paraphyletic.

A December 2006 survey found no members of Lipotidae (commonly known as the Yangtze River dolphin) and declared the species functionally extinct.

The current classification of river dolphins is as follows:

• Superfamily Platanistoidea
  • Family Platanistidae
    • Genus Platanista
      • South Asian river dolphins, Platanista gangetica, with two subspecies
        • Ganges River dolphin (susu), P. g. gangetica
        • Indus River dolphin (bhulan), P. g. minor
  • Family †Allodelphinidae (Miocene)
  • Family †Squalodelphinidae (Oligocene to Miocene)
  • Family †Squalodontidae (Oligocene to Miocene)
  • Family †Waipatiidae (Oligocene to Miocene)
• Superfamily Inioidea

• • Family Iniidae
    • Genus Inia
      • Amazon river dolphins (boto), Inia geoffrensis
        • Inia geoffrensis geoffrensis
        • Inia geoffrensis boliviensis
        • Inia geoffrensis humbotiana
    • Genus †Meherrinia (late Miocene)
  • Family Pontoporiidae
    • Genus Pontoporia
      • La Plata dolphins (Franciscana), Pontoporia blainvillei
• Superfamily †Lipotoidea
  • Family †Lipotidae
    • Genus †Lipotes
      • Baiji (or Chinese river dolphin), †Lipotes vexillifer (functionally extinct, since December 2006)

In 2012 the Society for Marine Mammalogy began considering the Bolivian (Inia geoffrensis boliviensis) and Amazonian (Inia geoffrensis geoffrensis) subspecies as full species Inia boliviensis and Inia geoffrensis, respectively; however, much of the scientific community, including the IUCN, consider the boliviensis population to be a subspecies of Inia geoffrensis.