British naturalist T.C. Jerdon visited Darjeeling in northern India in 1876, and collected the tree frogs. He preserved the frogs in a British museum.
But the frogs have resurfaced, said S.D. Biju, an amphibian enthusiast and lead researcher of a study released this week.
And he discovered their reemergence by chance.
"I was walking in the forests on another expedition when I heard distinct frog calls in the late evening hours," Biju said.
After bringing the old frogs to laboratories in India and comparing them, Biju and his team made a startling discovery: the frogs were an evolutionary outcome of the lost frog/specie and had a new set of genes.
Previously, scientists had overlooked this fact and missed the distinct lineage.
There are 7,500 amphibians in the world, and 400 are tree frogs, according to Biju. The frog family is classified into 17 categories, or genera, the more commonly used word.
Biju not only found the missing amphibian, but opened up the family to vast possibilities. He added an 18th genera, which he named Frankixalus jerdonii.
Biju and his team of researchers published their studies in the journal PLOS ONE this week.
The study revealed the remarkable characteristics of the frogs: they breed exclusively inside high canopy trees, and have distinct external appearances and skeletal features.
Perhaps the most intriguing and evolutionary feature is the mother's parental care. The tadpoles feed on the mothers eggs that she especially lays due to lack of food. The tadpoles also have no teeth, only flap-like papillae to swallow eggs.
While Biju and his team are excited with the discovery, he warns that the frogs face the threat of extinction.
"Frogs in this genus have specific microhabitat requirements and any small alteration can push frogs to extinction," he said.
Still, he is hopeful about the future. He plans to explore and document the region's wilderness and preserve India's rich biological heritage.