From the BBC:
At 7mm (0.27 inches) long, Paedophryne amauensis may be the world's smallest vertebrate - the group that includes mammals, fish, birds and amphibians.
The researchers also found a slightly larger relative, Paedophryne swiftorum.
Presenting the new species in PLoS One journal, they suggest the frogs' tiny scale is linked to their habitat, in leaf litter on the forest floor.
via the Gizmodo portion:
In fact, their calls have evolved to be strikingly similar to the chirps of insects.
According to the expedition's leader, Chris Austin from Louisiana State University in Baton Rouge, catching the frogs was easier said than done,
It was night, these things are incredibly small; so what we did after several frustrating attempts was to grab a whole handful of leaf litter and throw it inside a clear plastic bag. When we did so, we saw these incredibly tiny frogs hopping around.This evolutionary niche does have its drawbacks, however. Being so tiny, the frogs are often preyed upon by creatures like scorpions that otherwise couldn't take a frog.
I LOVE FROGS
Source -> http://www.bbc.co.uk/news/science-environment-16491477 via http://gizmodo.com/5875381/say-hello-to-my-little-friendthe-worlds-smallest-vertebrate
Earlier frog link -> http://www.dannyfinnegan.com/2011/11/live-tree-frog-found-in-costco-organic.html