Romer's Tree Frog (Liuixalus romeri) [huanqiu.com]

3. Romer's Tree Frog

Less than 0.8 inches long, the Romer’s tree frog of Hong Kong was once thought to be extinct following airport construction that wiped out its habitat. In good news, this tree frog is still alive, with active breeding programs contributing to a couple thousand Romer’s being released in the wild in the 1990s.