In 2011, scientists discovered the flea toad, also known as Brachycephalus pulex, in Brazil. This tiny amphibian may be the world’s smallest vertebrate, with some specimens being only 6.45 millimeters long. The frog was first described by scientists and is smaller compared to the previous record holder for the world’s smallest vertebrate.
Despite its small size and discovery in 2011, only a limited number of flea toad specimens have been collected from its habitat on forested hilltops in southern Bahia, Brazil. To verify the species’ maturity and sex, the gonads of the frogs were examined. It was found that only males have vocal slits.
Adult male B. pulex frogs are slightly over 7 millimeters long, smaller than females, making them smaller than the previously known smallest amphibian, Paedophryne amauensis frog from Papua New Guinea. The flea toad may be the smallest extant frog in the world due to these findings.
The study also highlighted how small these flea toads can get compared to other mini frogs at such scales they tend to develop unusual anatomical quirks like losing toes or having underdeveloped ears. Researchers also suggest that there may be even smaller vertebrates yet undiscovered leading to a possibility of another small frog or parasitic male of deep-sea anglerfish being the next record holder.