Everything about Platanistoidea totally explained
River dolphins are four living species of
dolphin which reside in freshwater rivers and
estuaries. They are classed in the
Platanistoidea superfamily of
cetaceans. Three species live in
fresh water rivers. The fourth species, the
La Plata Dolphin, lives in salt-water
estuaries and near-shore marine environments. However, it's scientifically classed in the river dolphin family rather than the
oceanic dolphin family.
Ecology
River dolphins are now facing extinction due to habitat loss, hunting by humans, and naturally low numbers. Also, many river dolphins possess very poor eyesight -- some are considered blind -- which can lead to unfortunate encounters with humans or human-made objects (boats or fishing nets, for example).
Some dolphin species can live in marine or riverine environments. The
Tucuxi, for example, is equally at home in both ecotypes. However, these are not classified in the Platanistoidea superfamily and are therefore not regarded as true river dolphins. Juvenile river dolphins are grey and turn pink at maturity.
Taxonomy
In the most recent classification (Rice, 1998) there are currently four extant
families that make up the river dolphins. However, a December 2006 survey found no members of
Lipotidae (commonly known as the
Yangtze River dolphin) and declared the species functionally
extinct,
Platanistidae is 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.
Classification by Rice (1998)
- Superfamily Platanistoidea
- Family Platanistidae
- Family Iniidae
- Amazon River Dolphin (or Boto), Inia geoffrensis
- Family Lipotidae
- Family Pontoporiidae
Previous classification
Family Platanistidae
- Ganges River Dolphin, Platanista gangetica
- Indus River Dolphin, Platanista minor
- Amazon River Dolphin (or Boto), Inia geoffrensis
- Chinese River Dolphin (or Baiji), Lipotes vexillifer (presumed extinct as of 2006
- La Plata Dolphin (or Franciscana), Pontoporia blainvillei
Extinction
On Dec. 13th, 2006, the Yangtze River Dolphin, or Baiji, was declared "functionally extinct", after a 45-day search by leading experts in the field failed to find a single specimen (External Link
). The last verified sighting of the beak-nosed dolphin was in September of 2004. (External Link) However, in August, 2007, reports surfaced that a man saw and videotaped what appears to be a baiji in the Yangtze River. A team of scientists will attempt to verify the sighting beginning in September, 2007. (External Link)
It is believed that overfishing,damming, and sub-aquatic sonar pollution (which interfered with the dolphin's sonar-based method of locating food), led to the extinction. Reuters news reported this their first record of a mammalian extinction in 50 years.
Further Information
Get more info on 'Platanistoidea'.
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