The bat was first discovered in 1979 in the forests of Ecuador
Scientists have discovered a tiny new species of bat in the western slopes of the Andes in northwestern Ecuador.
The first specimen of the species, which has been called Myotis diminutus, was collected more than 30 years ago.
But the researchers have only now confirmed that the little creature, which weighs just a few grams, is a distinct species.
They published a detailed description of the bat in the journal Mammalian Biology.
There are more than 100 species of Myotis bat, six of which can be found in Ecuador.
The bat's narrow skull helped the scientists distinguish it as a new species
But "diminutive Myotis", as the researchers have called it, is the smallest of this group of species yet known in South America.
The little brown bat weighs just 3.5g.
The scientists, based in Rio de Janeiro, Brazil and Washington DC in the US, wrote in the journal: "As with many other newly described species, we know nothing about the natural history of this bat.
"Unfortunately, the prospects for learning more about it are bleak."
This is because the moist forests of western Ecuador, where the bat was discovered, are under threat, primarily from deforestation for agricultural purposes.
The researchers say the area faces an "uncertain future".
The bat was found in a protected private reserve within the forest called the Río Palenque Scientific Center (RPSC).
"Myotis diminutus is at least the fifth new species of mammal described from the area in recent decades," the scientists wrote.