It was found that the fossil found in Ono City, Fukui Prefecture, may be the oldest mammal in Japan, and is considered to be a species that has never been reported.
The Fukui Prefectural Dinosaur Museum surveyed states that it is "a valuable resource that shows the diversity of mammals in the era when dinosaurs lived."
According to the Fukui Prefectural Dinosaur Museum, the fossil was found in the early Cretaceous strata 127 million years ago in the mountains of Ono City in June.
A fossil of the lower jaw with three teeth, 13.1 mm long and 5.8 mm high, was investigated in detail at the Fukui Prefectural Dinosaur Museum.
As a result, the shape of the teeth with three protrusions and the groove of the lower jaw seen at the stage of evolution from reptiles to mammals were confirmed, so the primitive mammal "Shinzo" with a body length of 16 cm to 17 cm was confirmed. It means that it turned out to be a reptile.
According to the museum, the fossil mammals found in the strata 130 to 121 million years ago in Hakusan City, Ishikawa Prefecture are the oldest in Japan, and this fossil is also found in the strata of almost the same age. So it could be the same age or older.
It is also a type of "true triconodonta" that has never been reported.
Kazushu Miyata, a senior researcher at the Fukui Prefectural Dinosaur Museum, who conducted a fossil survey, said, "It is a species that has not been reported in Japan and is a valuable resource that shows the diversity of mammals in the era when dinosaurs lived."