Chinese river dolphin

The Chinese river dolphin (Lipotes vexillifer)  or baiji  was a river dolphin. It was found only in the Yangtze River in China.  The last confirmed sighting of the baiji was in 2004 but there were possible sightings in 2007 and 2016 as well. The baiji was declared functionally extinct in 2007.  that means experts said that even if there had been a few baiji left alive in 2007, there were probably not enough left to have young and keep the species alive. The IUCN Red List says the baiji is critically endangered but not really extinct.
 Description 
The baiji was a graceful animal, with a long, narrow and slightly upturned beak and a flexible neck. As opposed to some other freshwater dolphins, like the Indus River dolphin, its eyes were functional, although greatly reduced. Its coloration was bluish-gray to gray above and white to ashy-white below. It weighed 135 – 230 kg (300 - 510 lb) and measured as much as 2.5 m (8.2') in length.

 Reasons for extinction 
The World Conservation Union (IUCN) noted these threats to the species: 
a period of hunting by humans during the Great Leap Forward, 
entanglement in fishing gear, 
the illegal practice of electric fishing, 
collisions with boats and ships, habitat loss, and 
pollution. 
Further studies have noted the environmental impact of building the Three Gorges Dam on the living space of the baiji.Walters, Mark Jerome (November 1993). "Who speak for the baiji?". Animals (EBSCO) 126 (6): 6–6.

It was the first dolphin species that humans have made extinct.

 References 

Category:River dolphins