Garuva (Brasil) (AFP) - Brazilian scientists announced Wednesday the discovery of three previously unknown species of poisonous toads in the fast-shrinking Atlantic forest of southern Brazil, an area dubbed an "incubator" of new life forms.

The tiny creatures, measuring from one to 2.5 centimeters (up to one inch), were found in Santa Catarina state, a zone of mountains and forested valleys that is considered an important center of biodiversity.

"The great importance of this discovery is that this forest serves as an incubator for the origin of species," said Marcos Bornschein, a researcher with the Federal University of Parana, who helped identify the creatures.

"It's a laboratory of huge importance for the mapping and conserving and understanding of biological processes," he said.

The Atlantic forest once covered most of Brazil's coastline, but only eight percent has been preserved. Most of the country's 204 million people live along the coast.

The toads are dark brown with red markings and are speckled with warts. They eat ants and mites and during digestion create a chemical in the skin that can poison predators, principally snakes.

"They are not dangerous to humans," Bornschein said. "During the fieldwork, some researchers felt a numbing in their finger ends after touching them, but nothing more."

The discovery of the toads, all classified as part of the Melanophryniscus genus, was described Wednesday in the scientific journal Plos One.

The article said that the discovery of the toads in a fairly restricted geographical area -- they were found between the cities of Garuva and Blumenau, about 100 kilometers (60 miles) apart -- suggested that the species "might be severely underestimated."

But it added that the "status of these species is of particular concern, given that one of them is at risk of extinction."