FROGS re-evolved 'lost bottom teeth after more than 200 million years, according to new research. Tree-dwelling Gastrotheca guentheri are the only frogs with teeth on both their upper and lower jaw. The reappearance of these lower teeth after such a long time fuels debate about whether complex traits are lost in evolution or if they can resurface. Scientists suggest this new evidence identifies a loophole in previous theories. Commonly known as marsupial frogs, the Gastrotheca genus carry their eggs in pouches. Unlike marsupial mammals such as kangaroos however, the frogs pouches are on their backs. The species Gastrotheca guentheri is even more unusual, being the only known frog to have teeth on its lower jaw. BBC