Scientists have discovered the oldest-known tadpole fossil dating back 161 million years in Argentina, offering unprecedented insight into the evolution of frogs. This fossil, belonging to the extinct species Notobatrachus degiustoi, is remarkably well-preserved, showing imprints of soft tissues such as eyes and nerves, and demonstrating that the tadpole stage existed during the Jurassic period. Measuring about 16 centimeters, it resembles modern tadpoles in structure, indicating that their survival strategy has remained largely unchanged over millions of years. This discovery narrows the timeframe for when frogs evolved their distinctive two-stage life cycle involving a tadpole phase. Previously, tadpole fossils were known only from the Cretaceous period, making this find significant in bridging a substantial gap in the fossil record. The results, published in Nature, contribute to understanding the evolutionary timeline and adaptive strategies of amphibians.