The creatures thought to be new to science also include three types of "glass frog", which get their names from the fact that their skin is so thin that internal organs can show through it.

A new harlequin frog, another species of rain frog and a salamander have also all been found.

The discoveries were made during a three-week expedition to Colombia's mountainous Tacarcuna area of the Darien, close to the border with Panama, led by scientists from Conservation International and the Ecotropico Foundation.

The survey, under Conservation International's rapid assessment programme, turned up around 60 species of amphibian, 20 reptiles and almost 120 species of bird - many of which are thought to be found nowhere else.

In addition, some Central American species including a rain frog, a small lizard, a salamander and an as-yet unidentified snake, were recorded for the first time in this northern area of South America, the scientists said.

Other species such as the endangered Baird's tapir, the Geoffroy's spider monkey and the white-lipped peccary were also recorded.

Conservation International said the high incidence of new species of amphibian - which are important indicators of environmental problems because they are vulnerable to pollution such as acid rain and pesticides, and to climate change - was cause for hope.

Jose Vicente Rodriguez-Mahecha, scientific director of Conservation International Colombia, said: "Without a doubt, this region is a true Noah's Ark.

"The high number of new amphibian species is a sign of hope, even with the serious threat of extinction that this animal group faces in many other regions of the country and the world."

Colombia has one of the most diverse collection of amphibians in the world, with 754 species currently recorded.

Worldwide a third of amphibian species, which include frogs, toads, newts and salamanders, are threatened with extinction as a result of disease, habitat destruction and climate change.

The Darien region of Colombia, which is isolated from the Andes, is recognised as an area of high biological diversity but is threatened by hunting, mining, illicit crop cultivation and habitat destruction.

Conservation International hopes the study of the area will contribute to strengthening protection of the region.

by:telegraph