This is likely the smallest frog species in the world, discovered in the Andes Mountains' upper Cosnipata Valley in Peru. From National Geographic:
"The most distinctive character of the new species," scientists write in the February issue of the journal Copeia, "is its diminutive size." Females grow to 0.49 inch (12.4 millimeters) at most. Males make it to only 0.44 inch (11.1 millimeters).Coin-Size Frog Found -- One of World's Smallest
What's most surprising is that the frog lives at such high elevations, said study co-author Alessandro Catenazzi, a postdoctoral researcher at the University of California, Berkeley. In general, larger animals are found at greater heights.