Fossil clue to vanished lake

The bone of the snake-bird

TT, New Delhi, May 28: Scientists have discovered India's first fossil of an ancient snakebird from a 2.6 million-year-old site in the Siwalik Hills that they say suggests the existence there of a vast lake that has since vanished.

The remains of the snakebird, also called a darter, found alongside fossils of a pelican, crabs, fish, crocodiles and turtles, indicate that the site 40km northeast of Chandigarh had a large body of water, palaeontologists from Panjab University, Chandigarh, said.

The scientists believe the fossil may represent an ancestor to the present-day Oriental darter, a waterbird that has a pointed bill it uses to spear fish and is found across the country, except in the Himalayan and northwesternmost regions.

"These fossils are significant because they help fill a gap in the fossil record of darters," Rajeev Patnaik, a scientist who was part of the study team, told The Telegraph.

A research paper by Patnaik and his colleagues who collaborated with Thomas Stidham, a senior faculty member at the Institute of Vertebrate Palaeontology and Palaeo-anthropology at the Chinese Academy of Sciences, Beijing, describing the fossils appeared on Wednesday in the journal PLOS One.

Darter fossils have earlier been documented from across the Old World - from sites in Thailand, Ethiopia, Kenya, Hungary and Australia.

While scientists have since the 19th century recovered fossils of pelicans, storks and ostriches from multiple sites across India and Pakistan, until now no one had found darter fossils.

Patnaik said the three bone fragments, including sections of the leg bone, were not sufficient for palaeontologists to identify the specific species of darter.

The site has an abundance of other fossils associated with aquatic life, including crabs, crocodiles, fish and a pelican, which the scientists believe indicates the presence of an ancient lake that gave way to the present-day hilly terrain.

"This area was a part of the Indo-Gangetic plains 2.6 million years ago," Patnaik said. "But over time, tectonic movements pushed some sections of the plains into the Siwalik Hills."

The scientists said the mammalian fossil records from the Siwalik Hills have also long pointed to a "turnover event" about 2.58 million years ago, when some species disappeared and others entered the scene.

Patnaik said this turnover event appeared to have been associated with a relatively warm and humid climate shifting towards increasing aridity.

"Along with this, some large herbivores such as ancient hippos went extinct in the region around the Himalayan foothills, and wild horses from America moved into the Indian subcontinent."

These changes coupled with tectonics, the scientists speculate, may have caused the lake and the darters to vanish.