Pliocene otoliths from NW India reveal first fossil osphronemid and structure of a Himalayan freshwater ecosystem

Abstract

The Neogene Siwalik deposits have long been recognised for their rich terrestrial fossil record, yet their freshwater ichthyofauna remains virtually unknown. This gap limits our understanding of past aquatic ecosystems and the biogeographic history of South Asian freshwater fishes. In this study, we report the first fossil record of freshwater fish otoliths from the Upper Siwalik Pliocene deposits of Mohand, Saharanpur district, in the northwestern Himalaya, India. Three taxa Channa (Channidae), Trichogaster fasciata (Osphronemidae), and Gobiidae indet. were discovered through our extensive bulk sampling. Among these, T. fasciata represents the second known fossil record of Osphronemidae globally and the first based on otoliths. The assemblage reflects a structured trophic composition composed of mid-level preys and apex predators. These faunal components suggest a calm, possibly lentic freshwater habitat with dense vegetation, consistent with the spawning behaviour of labyrinth fishes and the hunting of snakeheads. Despite the limited number of otoliths, this collection provides rare but significant insights into Pliocene freshwater biodiversity in the Himalayan region.

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