India’s first gourami fossil found in UP’s Siwalik foothills, reveals 4.8-million-year-old freshwater ecosystem

The study, ‘Pliocene otoliths from NW India reveal first fossil osphronemid and structure of a Himalayan freshwater ecosystem’, was published in Springer Nature on March 31.

Dr Singh said that these fossils have been found in Sumatra, but the exact age of the fossil locality of Sumatra is uncertain due to a lack of stratigraphic clarity. “Our findings from Mohand are dated 4.8 million years old,” he said.

Siwalik Group, which ranges in age from 18.3 to 0.22 million years old, is a freshwater deposit exposed along the length of the Himalayan foothills that stretches from the Potwar Plateau of Pakistan in the west to Assam in the east.

“More importantly, the region is well-known for its mammalian fossils, including primates, rodents, and other mammals. However, the fossil record of freshwater fishes from this region remains sparse, leaving many questions regarding their past distributions and palaeobiodiversity unknown,” the paper said.

The fossil evidence, according to the paper, suggests that during the Pliocene, the area had a calm, stable freshwater body surrounded by dense vegetation. This is inferred from the presence of Osphronemidae, a family that includes living gouramis, which prefer still water, and Channa, to which snakeheads, ambush predators, belong.

“Freshwater fish otoliths are rarely found in the Siwalik region of the Indian Subcontinent. Singh et al previously reported otoliths of Channa aff. striata [a snakehead fish similar to the modern striped snakehead, but not definitively identified as that species] from the Pinjor Formation, Upper Siwalik, exposed in the Nadah area of Haryana district, India,” the paper said. “Bhandari et al. mentioned an otolith locality when describing rodent fossils from the region, but did not provide any details. Since then, there have been no new records of freshwater otoliths from the Siwaliks of the Indian Subcontinent. Among the recovered otolith specimens, we also document the second known record of Osphronemidae in the fossil record”.

It went on to say: Despite the limited number of otoliths, our findings provide valuable data for reconstructing past freshwater ecosystems and insight into the historical biogeography of Anabantoidei in South and Southeast Asia”.

Moreover, most fossils found in this region so far have been of land animals, especially mammals. The newly discovered otoliths from the Pliocene period provide clear evidence that freshwater fish were also part of the ecosystems in northern India at that time, giving a more complete picture of past biodiversity in the region. Although only a small number of otoliths have been found, this study still offers important insights into how freshwater fish were distributed in the past, including the history of the gourami family.

More fossil discoveries and further sampling could identify more species and help scientists better understand these ancient freshwater ecosystems.