Discovery of Limnospondylus ajimuensis

Researchers from Kyoto University have identified a new genus and species of giant salamander, Limnospondylus ajimuensis, based on three fossilized vertebrae discovered in the Ajimu region of Japan. Dating back approximately 3.5 million years to the Pliocene epoch, this amphibian inhabited warm, humid wetlands and reached lengths of about 1.1 meters. The discovery provides critical evidence of ancient biodiversity in Asia and helps bridge a 20-million-year gap in the fossil record of the Cryptobranchidae family. The study, published on June 3, 2026, in the journal PeerJ, highlights the importance of re-evaluating existing museum collections that were previously misclassified under the genus Andrias. By identifying unique anatomical features in the mid-trunk vertebrae, the team demonstrated that ancient giant salamanders were more diverse and occupied a broader range of freshwater environments than their modern descendants, which are now primarily restricted to flowing river systems. This research underscores the evolutionary resilience of the giant salamander lineage, which has persisted for nearly 60 million years. The findings serve as a reminder of the ecological shifts caused by global cooling at the end of the Pliocene, which likely drove the extinction of specialized lake-dwelling species like Limnospondylus while allowing river-adapted relatives to survive into the modern era. For researchers and conservationists, this discovery emphasizes the necessity of protecting extant giant salamander populations, such as Andrias japonicus, from contemporary threats like habitat destruction and hybridization. The study provides a foundational framework for future paleontological investigations and reinforces Japan's status as a vital region for understanding the evolutionary history of amphibians.