File under slightly slimy, but oh-so super cute.

Introducing: The world's tiniest frogs; amphibians that easily fit on a penny.

Fred Kraus, vertebrate biologist at the Bishop Museum in Honolulu, Hawaii, found the miniature frogs that span 0.4 inches (8 to 9 millimeters) in length in the forests of Papua New Guinea.

The two species, Paedophryne dekot and Paedophryne verrucosa, bumped off the world's-smallest-frog list the Monte Iberia Eleuth, an elusive frog found on a single mountain in Cuba.

Miniaturization occurs in many frog genera around the world, Kraus said in a statement. New Guinea seems particularly well represented, with species in seven genera exhibiting the phenomenon. Although most frog genera have only a few diminutive representatives mixed among larger relatives, Paedophryne is unique in that all species are minute.

Kraus suggested in the discovery, published in the journal ZooKeys on Monday, suggested that the lowest limits not only of frog size, but of any four-legged creature, had been reached.

For example, the female frogs only possessed two eggs, restricting their ability to reproduce.

It is uncertain whether the presence of so many minute frogs in the Papuan region represents a biological oddity of that region or whether similar frogs have simply been overlooked or underappreciated elsewhere, Kraus wrote in the report. Given the difficulty of locating miniaturized frogs in the field and the rate at which they've been discovered during the past 15 years, additional miniaturized species no doubt await discovery or description in other poorly surveyed areas of the tropics.

The report inspired other news organizations to pull out file photos of tiny, cute animals.

Other blogs and posts previously displayed some of the world's smallest animals, such as here or here.