A frog smaller than a human fingernail may be the world's smallest vertebrate

According to researchers at Santa Cruz State University in Brazil, the Brazilian flea frog (Brachycephalus pulex) is only 7-8mm long, possibly the smallest vertebrate on Earth.

The Brazilian flea frog (Brachycephalus pulex) is only 7-8mm long, possibly the smallest vertebrate on Earth.

In 2011, Mirco Solé, a researcher at Santa Cruz State University in Brazil discovered the tiny Brazilian flea frog , an amphibian so small it could comfortably fit on a small coin.

This frog is a candidate for the title of "world's smallest vertebrate". (Photo: Renato Gaiga).

The discovery made headlines in the scientific community, but because there was only a small sample, there was no way to provide conclusive information about the frog's size.

Now, more than a decade later, a team led by Mirco Solé has published an extensive study of the elusive frog that can only be found on two forested hillsides in Bahia, Southern Brazil.

Research shows that the flea frog is a very likely candidate for the title of "world's smallest vertebrate".

In their new study, the researchers went to the small frog's habitat again to collect a larger number of specimens, with 46 individuals.

The researchers examined the frogs' size, gonads to determine their sexual maturity, and tested for the presence of vocal slits, which are unique to males. They discovered that males are just over 7mm long, while females are slightly larger, just over 8mm.

Interestingly, the smallest adult specimen measured during the study was only 6.4mm long, 30% smaller than the smallest frog ever observed before.

Although there may be even smaller frogs, the researchers point out that the smallest individuals often have deformities, such as fewer toes or a complete lack of ears, which suggests that they wouldn't be able to survive if they were any smaller.