For 20 years these tiny frogs have been sat without a scientific name. Until now.
Meet Stumpffia kibomena – Madagascar’s newest species of frog.
This bright-bellied frog gets its name from the Malagasy words ‘kibo’ meaning ‘belly’ and ‘mena’ meaning ‘red’.
The new species has been described in a paper published in Zootaxa.
Lead author, Dr Frank Glaw from the Zoologische Staatssammlung in Munich, Germany recalled his first encounter: “When I found Stumpffia kibomena for the first time in early 1995, I was very excited about this beautiful discovery.
"Due to its distinctive colouration with its bright red belly it was immediately clear to me, that this was a new species."
However, he explained that other research priorities meant it remained undescribed for two decades.
The patterning on their backs is variable, but all individuals have strong red colouration on their bellies and undersides of their hind legs and arms. They also sport a black throat.
S. kibomena has been found active at different times of day and night and in a variety of habitats, but very little else is known about its lifestyle.
One thing the authors have noted is its distinctive call with a high note repetition rate of 1.3 notes per second, which is higher than in all other described species in which advertisement calls are known.
Only recent developments have allowed DNA analysis of S. kibomena specimens to help confirm its place as a new species.
“It was always clear that Stumpffia kibomena was a new species, but since genetic studies have become very important in species recognition during the last 15 years, it is now desirable to describe new species only together with DNA sequence data," explained Dr Glaw.
“With the newly available DNA sequences, we had a comprehensive dataset for the new species and described it.”
And despite only measuring between 18 to 21mm, S. kibomena could be considered somewhat of a giant within the Stumpffia genus.
Two of the smallest species of frogs in the world belong to this genus – S. tridactyla and S. pygmaea – with the former only attaining sizes half that of S. kibomena.
"FrogchartX" by Xiaphias - created by Xiaphias. Licensed under CC BY-SA 3.0 via Wikipedia
In the last 25 years, Dr Glaw and colleagues have named approximately 160 new species of amphibians and reptiles from Madagascar, which is approximately 1% of the world’s herpetofauna.
“In Madagascar, 300 described amphibian species are currently known but we have identified more than 250 additional candidate species which are waiting to be studied in detail and to be described formally,” said Dr Glaw.
Not all of these mystery specimens will turn out to be new species, but they provide rays of hope in a cloudy, uncertain world for amphibians.
Many species are in serious decline worldwide and almost one third of all amphibians are threatened according to the IUCN Red List assessment.
We are just starting to understand the biodiversity of Madagascar and, unfortunately, it is likely that many species will become extinct before they have been named by scientists.
Madagascar is no exception, with habitat destruction, environmental pollution and the recent arrival of chytrid fungus – the killer frog disease – all posing serious threats to Madagascar's unique amphibians.
So far, no mass mortalities caused by chytrid fungus have been observed on the island and according to Dr Glaw, there are still "plenty of frogs" in the rainforests.
"I really hope that this will not change! Madagascar harbours many species with small distribution ranges – so-called micro-endemic species – and those are especially vulnerable to chytrid," said Dr Glaw.
However, he believes habitat destruction poses the biggest and most imminent threat to Madagascar's frogs.
"We are just starting to understand the biodiversity of Madagascar and, unfortunately, it is likely that many species will become extinct before they have been named by scientists," he said.
You can follow BBC Earth on Twitter, Facebook and Instagram.