Reconstruction of palaeoecology and palaeoclimate using reptilian fauna from the miocene and pliocene siwalik deposits exposed in and around Ramnagar Jammu and Kashmir Haritalyangar and Nurpur Himachal Pradesh

Abstract

This study investigates the palaeoecology and palaeoclimate of the Siwalik Group in Northwest India from the Middle Miocene to Plio-Pleistocene, utilizing fossil reptilian assemblages as key environmental proxies. Fieldwork and analysis of fossils from Ramnagar (Middle Miocene), Haritalyangar (Late Miocene), and Kanthro/Chandigarh (Late Pliocene/Pleistocene) involved systematic collection and detailed taxonomic identification using comparative anatomy, shell histology, SEM, and micro-CT. Key findings reveal distinct environmental shifts: the Middle Miocene Ramnagar sites (~14 12.7 Ma) indicate a warm, perennially humid, forested landscape with stable freshwater systems, evidenced by Acrochordus dehmi, diverse crocodilians (Gavialis, Crocodylus), and varied turtle fauna. Conversely, the Late Miocene Haritalyangar locality (~9.1 Ma) signifies a transitional phase with increased climatic seasonality and reduced water permanence, linked to monsoon intensification and the rise of C4 vegetation. Finally, the Late Pliocene/Pleistocene sites (~3 Ma onwards) reflect cooler, C4 grassland-dominated ecosystems, though the presence of Geoclemys hamiltonii and Crocodylus palaeindicus confirms the persistence of crucial freshwater refugia. This research demonstrates that fossil reptiles are sensitive indicators of past hydrological and thermal regimes, refining our understanding of the dynamic interplay between climate, tectonics, and biotic evolution in the Siwalik foreland basin. newline