Researchers announced Thursday the discovery of the smallest known vertebrate - a frog from New Guinea that not only fits on a U.S. dime, but has enough space to invite four or five fellow species.

The frog, Paedophryne amanuensis, was discovered by a team of U.S. scientists and measures a paltry 7.7 millimeters (0.3 inches), about the thickness of an iPod Touch.

The online journal PLoS ONE published the finding Thursday.

The result came just a month after a vertebrate biologist Fred Kraus at the Bishop Museum in Honolulu, Hawaii announced two related frog species in New Guinea as the smallest: Paedophryne dekot and Paedophryne verrucosa.

At the time, Kraus said his discovered tiny frogs that measured 8-9 millimeters (0.4 inches) suggested the lowest limit for vertebrate evolution.

The authors wrote that only teleofish reach such levels of miniaturization in the wild.

But the question remains - why did the frogs evolve to become so small? Miniaturized animals typically are less prolific, are more sensitive to desiccation and have simplified bodies that can impede a species in evolution.

All three frog species were found in wet-forest litter, which may allow the little ones to adapt and decrease their size to avoid predators.

This discovery highlights intriguing ecological similarities among the numerous independent origins of diminutive anurans [frogs], suggesting that minute frogs are not mere oddities, but represent a previously unrecognized ecological guild, the researchers wrote in their article.

Such discoveries are increasingly critical in this time of global amphibian declines and extinctions, the authors concluded.