Scientists have identified a previously unknown genus and species of giant salamander from fossils found in Japan more than two decades ago. The creature, named Limnospondylus ajimuensis, lived about 3.5 million years ago and may have grown to 1.1 meters long.
The fossils, three vertebrae from the Cryptobranchidae family, were uncovered in the late 1990s in the Ajimu area of Oita Prefecture. They came from the Tsubusugawa Formation, ancient lake sediments dating to the Pliocene epoch. Researchers initially assigned them to the genus Andrias but later analysis showed distinct features.
A team from Kyoto University reexamined the specimens and compared them with living species. The mid-trunk vertebra displayed unique anatomical traits not seen in other known giant salamanders. This led to the creation of a new genus, Limnospondylus, with the species name ajimuensis referring to the discovery site.
First author Masahiro Noda noted that Ajimu is the only site worldwide where fossils of both the giant salamander family and extant genera have been found. He emphasized Japan's importance in understanding their evolutionary history. The salamander inhabited warmer, wetter freshwater lakes and marshes that once covered parts of Kyushu.
Cooling temperatures and habitat changes at the end of the Pliocene likely contributed to its extinction. Its relative, the Japanese giant salamander, survives today in the same region.