White Finless Porpoise

Quick answer：

The White Finless Porpoise (Neophocaena phocaenoides), also known as the Yangtze River dolphin, is an endangered marine mammal species native to the Yangtze River in China. Once abundant, it has been severely impacted by human activities and is currently listed as critically endangered. The species is known for its distinctive lack of a dorsal fin and its grayish-white coloration.