Which Is The World´s Smallest Vertebrate?

It is a fly-size frog

The record was broken about 2 years ago by Paedophryne amauensis, which has an average length of only 7.7 mm. Actually, it's a double record, as Paedophryne amauensis became both the world's

smallest known frog and the smallest known vertebrate.

The existence of a frog that is just a bit bigger than the common fly is really mind-blowing!

Why so small? 

Austin believes that P.amauensis and other tiny frog species have evolved this way in an effort to fill a niche that nothing else is filling. Their tiny size allows them to consume very small invertebrates, like mites, that no other predator eats.

Description
P. amauensis has an average body length of only 7.7 millimetres (~0.30 in) and comes with dark-brown, earth-like colors that allow it to blend in with the leaves of the forest floor. Individuals are essentially invisible to the naked eye.

Their skeleton is reduced and there are only seven presacral vertebrae present.

Discovery
The species was discovered in August 2009, by Louisiana State University herpetologist Christopher Austin and his PhD student Eric Rittmeyer, during an expedition to explore the biodiversity of Papua New Guinea. It was formally described in January 2012, and was discovered near Amau village in the Central Province.

In their paper, the researchers note that discovering the species was not easy. Male frogs use calls that resemble sounds made by insects and both sexes camouflage themselves in the leaves of the forest floor. These two traits, combined with their tiny stature is most probably why the species has gone unnoticed for such a long time.

To catch them, the researchers resorted to sound triangulation, as the high pitch of the calls made them especially hard to locate using human hearing.

Finding the frogs was not an easy assignment. They are well camouflaged among leaves on the forest floor, and have evolved calls resembling those of insects, making them hard to spot. -"The New Guinea forests are incredibly loud at night; and we were trying to record frog calls in the forest, and we were curious as to what these other sounds were," said research leader Chris Austin from Louisiana State University in Baton Rouge, US. -"So we triangulated to where these calls were coming from, and looked through the leaf litter. -"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," he told BBC News. The Paedophryne amauensis was identified only recently, and consists of a number of tiny species found at various points in the eastern forests of Papua New Guinea.The tiny limbs of amauensis (top) and swiftorum are rendered translucent

They're occupying the relatively thick leaf litter of tropical forest in low-lying parts of the island, eating incredibly small insects that typically are much smaller than insects that frogs eat," said Professor Austin.

“And they're probably prey for a large number of relatively small invertebrates that don't usually prey on frogs."

Predators may well include scorpions.

Before the Paedophrynes were found, the title of "world's smallest frog" was bestowed on the Brazilian gold frog (Brachycephalus didactylus) and its slightly larger Cuban relative, the Monte Iberia Eleuth (Eleutherodactylus iberia). They both measure less than 1cm long.

The smallest vertebrates have until now been fish.
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