Paddlefish

Paddlefish (family Polyodontidae) are basal Chondrostean ray-finned fish.[2] 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.[3] Polyodontids are exclusively North American and Chinese.[4]
There are six known species: four extinct species known only from fossil remains (three from western North America, one from China), and two extant species, including the American paddlefish (Polyodon spathula) which is native 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.[5] Chinese paddlefish are also commonly referred to as "Chinese swordfish", or "elephant fish".[6][7]
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 since 2007, and may now be extinct for many of the same reasons that have plagued the American species.[8][9]
Category:Animals
Category:Creatures