World's smallest vertebrate (it's a frog)

Vertebrates are animals with an internal bone skeleton. Such animals include those of fish, amphibians, reptiles, birds, mammals, primates, rodents and marsupials. They are special because even though they make up only a small percentage of all animals, their size and mobility often allow them to dominate their environment.

A frog, paedophryne amauensis, found in Papua New Guinea is the world's smallest vertebrate, and hence the world's smallest frog.

It's length is a mere 0.3".

Before the frog was discovered, the smallest was a fish from Indonesia called Paedocypris progenetica, with an average length of 0.3".