Highlighting a "vast underestimation" of Madagascar's natural riches, up to 221 new species of amphibians have been found on the island country, including the frog Boophis ulftunni, pictured. The find nearly doubles the number of known amphibians in Madagascar, a new study says.

Boophis frog
© Miguel Vences
An international team of scientists discovered the new species after collecting 2,850 specimens from more than 170 sites, including the country's most visited and studied national parks.

The work suggests that tropical amphibian diversity has been underestimated at an "unprecedented level" worldwide, the study authors write in the May 4 online edition of the journal Proceedings of the National Academy of Sciences.

"People think that we know which plant and animal species live on this planet," team member Miguel Vences, of the Technical University of Braunschweig in Germany, said in a statement.

"But the century of discoveries has only just begun - the majority of life-forms on Earth is still awaiting scientific recognition."