Paddlefish

Paddlefish (family Polyodontidae) are basal Chondrostean ray-finned fish. They have been referred to as "primitive fish" because they have evolved with few morphological changes since the earliest fossil records of the Late Cretaceous, seventy to seventy-five million years ago.Polyodontids are exclusively North American with the exception of the genus Psephurus, which includes solely the Chinese paddlefish (Psephurus gladius).

There are five known taxa: three extinct taxa from western North America, and two extant taxa, including the American paddlefish (Polyodon spathula) which is endemic to the Mississippi River basin in the U.S. and the critically endangered Chinese paddlefish (Psephurus glades) which is endemic to the Yangtze River Basin in China. Chinese paddlefish are also commonly referred to as "Chinese swordfish", or "elephant fish".

Paddlefish populations have declined dramatically throughout their historic range as a result of overfishing, pollution, and the encroachment of human development, including the construction of dams that have blocked their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed natural flows resulting in the loss of spawning habitat and nursery areas. Chinese paddlefish have not been seen in the wild since 2003, and may now be extinct for many of the same reasons that have plagued the American species.