A New Species of Fossil Nymphalidae (Lepidoptera, Papilionoidea) from the Upper Pliocene Motojuku Group, Gunma Prefecture, Japan

Abstract. In this study, we describe and illustrate a new fossil species of Nymphalidae (Lepidoptera, Papilionoidea), Neptis kabutoiwaensis sp. nov., based on an impression fossil from the Upper Pliocene Motojuku Group, Gunma Prefecture, central Japan, which is the first fossil representative belonging to the subfamily Limenitidinae of Nymphalidae. In addition, our study is the first to report the discovery of a named Papilionoidea fossil from the Pliocene Series. The fossil shares characteristics, such as the reduced forelegs, open discal cell in the forewing, and short Sc + R1 vein in the hindwing, with the tribe Neptini of Limenitidinae. However, the presence of the CuP vein in the forewing suggests that the studied fossil is clearly different from known species of tribe Neptini. This is an important discovery that can assist us in exploring the evolution of the tribe Neptini during the Pliocene, because this new species has the possible ancestral characteristic of a CuP vein in its forewing.