Taxonomic and Paleoecological Insights into Fish Community Responses to the Carnian Pluvial Event in the Northwestern Sichuan Basin

The Carnian Pluvial Event (CPE) was a major hyperthermal event of the Mesozoic that triggered substantial extinctions and turnovers in both marine and terrestrial biota. However, its impact on marine fishes (Chondrichthyes and Osteichthyes) remains poorly understood. This study investigates chondrichthyan and osteichthyan ichthyoliths from the Ma’antang (MAT) and Hanzeng (HZ) sections in the northwestern Sichuan Basin. The recovered ichthyoliths were systematically identified and described, and dental morphological analysis was used to infer feeding strategies and reconstruct food-web structure. The result show that species richness declined by approximately 67% across the CPE, accompanied by a reduction in community diversity. In addition, the disappearance of more than half of the fish taxa after the event likely led to the collapse of previously complex food webs, reducing trophic networks to a limited number of simplified food chains and contributing to ecosystem destabilization. Findings suggest that the CPE drove substantial biotic turnover in marine fish assemblages. Further integration of quantitative evidence from multiple regions and taxonomic groups will be essential to better constrain the magnitude and mechanisms of its impact on global marine biodiversity.