The new species named Kani maranjandu after the Kani tribe in Kerala, are substantially different from other congeners.
The characteristic traits of the crab include the structure of its hard upper shell, its male abdominal structure and reproductive parts and diagnostic elongated walking legs, which no other genus has, said researchers from University of Kerala.
This is the first report of its kind to offer a record of an arboreal crab - a species that lives in trees.
The survey of the freshwater crab fauna started in 2014 in the Westerns Ghats in Kerala. People from the Kani tribe reported sightings of a 'long legged' tree crabs in the area.
After a year, researchers were finally able to capture a female specimen and later a large adult male.
"As water holding hollows in large trees are essential for the survival of this unique species, the discovery also stress the need for conservation of large trees in the degraded forest ecosystems of the Western Ghats," said Biju Kumar of University of Kerala.
"It also highlights how little we know about the actual biodiversity that resides in these forests and the efforts that must still be made to find and study the many undoubted new species that still live there," Kumar said.
The finding was published in The Journal of Crustacean Biology.