Yangtze River Dolphin Recently (2006) determined as extinct. This animal was a freshwater dolphin that resided solely in the Yangtze River in China. Fossils date the species as old as 25 million years. Hirola Antelope Endangered. Those extra large scent glands (which get larger when excited) have earned it the nickname, "four-eyed antelope." Bumblebee Bat World's smallest mammal, right alongside the Etruscan shrew. They can hover like hummingbirds, and they weight about a much as a dime. Endangered. Golden-rumped elephant shrew Endangered.