In the late 1990s, scientists working in the Ajimu area of Oita Prefecture, Japan, discovered three fossil vertebrae from a giant salamander. Cryptodactylidae family. The bones were preserved in the Rusukawa Formation, a layer of ancient lake sediment from the Pliocene epoch, about 3.5 million years ago.
Other fossils found in the same formation include animals such as elephants and crocodiles that no longer live in Japan. These ruins indicate a time when the area was much warmer and wetter than it is today.
Researchers initially classified the Ajimuin fossil as a member of the genus Ajimuin. andriascontains the largest amphibians alive today. But scientists lacked enough comparative material and anatomical studies to determine exactly what type of giant salamander the bones represented.
More than 20 years later, a team of researchers from Kyoto University has examined the fossil and uncovered new details about its identity.
Salamander different from known species
The researchers compared the bones at Ajimu with the skeletons of living people. Cryptodactylidae seed. Their analysis revealed that the fossil consists of anterior, middle, and sacrococcygeal vertebrae.
The mid-dorsal vertebrae were particularly important because they contained anatomical features not seen in other known members of the salamander family. Based on these differences, the researchers concluded that the fossils belong to both a previously unknown species and a new genus.
“Ajimu is the only site in the world where fossils of both giant salamanders and extant genera have been discovered,” said lead author Masahiro Noda. “We are pleased that this study highlights Japan as an important region for understanding their evolutionary history.”
A 1 meter long giant from ancient Kyushu
Researchers named the species Limnospondylus azimuensis. The name is a combination of Greek words Limnemeaning lake; spinewhich means vertebrae, azimuensis About Ajimu.
Millions of years ago, this giant salamander lived in large freshwater lakes that covered parts of Kyushu. As an adult, it may have reached a length of about 1.1 meters.
only 5 genera of them Cryptodactylidae The giant salamander family has been previously described, and the recognition of a separate genus is an important addition to scientists’ understanding of giant salamander diversity.
Cryptodactylidae Fossils have been found throughout the Northern Hemisphere. However, due to limited anatomical knowledge, many specimens have been assigned to extant genera. andrias. The new discoveries raise the possibility that some of these fossils actually represent a large number of as-yet-unrecognized species.
climate change and extinction
Decreasing temperatures during the Pliocene to early Pleistocene transition and major changes in local habitat may have contributed to the disappearance of green sea turtles. Limnospondylus azimuensis.
their relatives, andrias japonicusGiant salamanders still inhabit rivers in the Ajimu area and other parts of Japan.
“In recent years, Japan’s native giant salamander has faced challenges such as hybridization with non-native species and habitat destruction,” says Professor Noda. “Through this research, we have once again realized the importance of preserving existing species for the future.”
