The world's smallest frogs, measuring only 8 to 9 mm in length, have recently been discovered by researcher Fred Kraus in southeastern New Guinea. The newly discovered frog species are also now the world's smallest tetrapods or non-fish vertebrates.

Researcher Fred Kraus said the frogs belong to the genus Paedophryne, whose species are extremely small. Kraus's had discovered Paedophryne from nearby area in 2002 but these were larger, with sizes of 10 to 11 mm. Still the genus represented the most miniaturized group of tetrapods in the world, the researcher said.

The two new species named Paedophryne dekot and Paedophryne verrucosa, however, were smaller measuring only 8 to 9 mm in length.

"Miniaturization occurs in many frog genera around the world," said the author, "but 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."

According Kraus, because the members of this genus have reduced digit sizes, they cannot climb well, thus inhabit leaf litter. Habitation in leaf litter and moss is common in miniaturized frogs and may reflect their exploitation of novel food sources in that habitat.

The study also found that because of the frogs' small body sizes, this have also reduced the egg complements that females carry to only two, and it is not yet known whether both eggs are laid simultaneously or at staged intervals.

The findings of the study were published in the open access journal ZooKeys.