GUARAQUECABA, Brazil: On a trek across an Atlantic rainforest reserve in south Brazil, biologist Michel Garey recalled how on his birthday in 2007 he chanced upon a new species of a tiny, three-fingered frogs.

“I was doing research with two friends on a hilltop in the reserve and I stumbled into this unusual frog with only three fingers,” he told a small group of reporters this week on a tour of Salto Morato, a nature preserve owned by Brazil’s leading cosmetic firm Boticario.

“It happened on February 14, 2007: My birthday. What a treat!” he said.

But it was not until June this year that the discovery of this new species—Brachycephalus tridactylus—was officially established. A report on his finding was published in Herpetologica, a quarterly international journal focusing on study and conservation of amphibians and reptiles.

“It took me 18 months from early 2011 to collect seven of the new frogs, go to museums to compare them with other species, realize that they were new, write my paper and have it published in the journal.”

The tiny brachycephalus tridac-tylus was found at an altitude of around 900 meters (3,000 feet). Its most striking feature is the absence of a fourth finger, which Garey attributes to an evolutionary process rather than to environmental effects.

The frog, which measures less than 1.5-centimeters in length, is mostly orange with olive-gray spots and dots on its body.

Garey said that the male frog makes around 30 mating calls a day, sounds he described as “a single short note that decreases in dominant frequency from beginning to end.”

Garey said that he could not estimate the frog population, but plans to do so in a future research project.

The frog is part of 43 amphibian species found in this 2,253-hectare (5,567-acre) reserve, located in Guaraquecaba, the easternmost city in the southern state of Parana.

Experts estimated that about 950 amphibian species live across Brazil and more than 6,700 around the world.