October 17, 2023
Keio University
Kagoshima University
Teachers Hiroaki Aiba and Yui Takahashi of Keio Yochisha Elementary School and Professor Yoshitaka Sakamaki of Kagoshima University have reported a fossil of a butterfly from the genusNeptis(family Nymphalidae) as a new species. This is the first time a new species of butterfly fossil has been reported from Japan. The stratum from which the fossil was excavated is the Maizawaso of the Honjuku Formation, Upper Pliocene, in Gunma Prefecture (approximately 3.5 million years ago), a site also long known as the Kabutoiwa Formation and recognized for yielding many plant and insect fossils.
Butterfly fossils are particularly rare among insect fossils, with only about 60 adult fossils having been discovered worldwide. Of these, about 40 species have been named. Moreover, more than half of these were reported in the 19th century, and there have been only two discoveries so far in this century.
This is the world's first report of a fossil from the genusNeptis, and it is also the world's first new species of butterfly fossil from the Pliocene epoch, making it the world's youngest extinct butterfly fossil species.
The morphology of this fossil's wing venation retains some primitive veins and could be valuable material for discussing butterfly evolution.
The results of this research were published on October 1, 2023, inPaleontological Research, the international journal of the Palaeontological Society of Japan. A photograph of it was also featured on the cover.
Please see below for the full press release.