(CNN) -- The world's smallest vertebrate -- animals that have a backbone -- is a frog that could sit within the confines of your fingernail, a new study reports.
Scientists found the new species, which on average is just 7.7 millimeters long, in the southwestern Pacific island nation of Papua New Guinea.
The frog, scientifically named Paedophryne amauensis, spends its life in moist leaf litter on the floors of tropical wet-forests. Males call out with a continuous series of high-pitched notes at dawn and dusk, resembling the sound of crickets, says Christopher Austin, associate professor at Louisiana State University who led the team that discovered the frog.
"We think the really small body size is an evolutionary adaptation to occupy this really moist, leaf litter niche in New Guinea," Austin said. Typically, small frogs dry out quickly, but this tiniest species has a habitat that stays moist for most of the year.
Describing their findings in the online research journal PLoS ONE, researchers say the animals have simplified skeletons and are born directly as frogs, as opposed to first going through a tadpole stage. Researchers believe these creatures eat even smaller animals, such as mites, Austin said.
The discovery "is of considerable interest to biologists because little is understood about the functional constraints that come with extreme body size, whether large or small," the report in the journal states.
Previously the smallest vertebrate was believed to have been a fish known as Paedocypris progenetica, which matures at 7.9 millimeters. There has been speculation that aquatic habitats are home to the world's smallest and largest vertebrates, but this frog contradicts that theory, Austin says.
Although the smallest frogs are just being reported on now, they are locally abundant, Austin said.
The discovery reveals that tiny frogs "are not merely curiosities, but represent a previously unrecognized ecological guild. Such discoveries are increasingly critical in this time of global amphibian declines and extinctions," the report says.
CNN's Elizabeth Landau contributed to this report.