A tree frog thought to have gone extinct 137 years ago has been rediscovered "by accident" in the jungles of north east India. The discovery was made by renowned Indian biologist Sathyabhama Das Biju and his team.

The only known specimens previously were collected by British zoologist Thomas Jerdon in 1870, who named them Polypedates jerdonii – though recent DNA analysis has shown that the frogs are in fact of a completely new genus, Frankixalus, which the researchers named after Biju's adviser at Vrije University, Franky Bossuyt.

Biju is known as The Frog Man of India, having discovered 89 of the 350 species found in the country.

The frogs were first found in 2007 during a search for other animals. "We heard a full musical orchestra coming from the tree tops. It was magical. Of course we had to investigate," said Biju.

It's thought the frogs have stayed hidden because they live in tree holes 19ft off the ground – there also has not been many research trips into the area they live. Researchers think the frogs may also be found in China and Thailand.

The female frogs lay their eggs in water-filled holes high in tree tops, returning when the tadpoles hatch to feed them unfertilised eggs.

tree frog Frankixalus
\"This is an exciting find, but it doesn\'t mean the frogs are safe.\" Biju et al / PLOS One

"This is an exciting find, but it doesn't mean the frogs are safe," said Biju. ""This frog is facing extreme stress in these areas, and could be pushed to extinction simply from habitat loss... We're lucky in a way to have found it before that happens, but we're all worried."