A rare butterfly fossil discovered decades ago in Japan was identified as a new extinct species, according to a study published on May 2 in the journal Paleontological Research. The fossil, which had remained unidentified for years in the Japanese Museum of Unique Fossil Insects, was classified as Tacola kamitanii, a species characterized by a wingspan of nearly 9 centimeters (approximately 3.5 inches).
The fossil was unearthed in 1988 in the town of Shin'onsen, located in the northeastern part of Hyogo Prefecture, approximately 180 kilometers northeast of Osaka. The area is renowned for the presence of insect fossils, and the specimen had been kept in the Unique Insect Fossils Museum, a repository of paleontological treasures.
Researchers noted that the discovery is important due to the extreme rarity of butterfly fossils. "Butterfly fossils are extremely rare," they noted. "Butterfly bodies and wings are fragile and buoyant, making them less likely to be preserved as fossils than other insect groups."
The species was named Tacola kamitanii in honor of Kiyoshi Kamitani, the discoverer of the fossil. This naming pays tribute to his contribution to the field when he found the specimen in Shin'onsen over three decades ago.
Tacola kamitanii belonged to the subfamily Limenitidinae, which today includes butterflies such as viceroys and admirals. This fossil represents the first named species officially described from the tribe Limenitidini and is the first fossil ever found of the subgroup, granting it particular importance in understanding butterfly evolution.
Based on the body size and abdomen structure, researchers determined that the specimen was female, noting its large body size and "very thick" abdomen.
The discovery of Tacola kamitanii is notable because it stands out as the youngest known extinct species among fossil butterflies. It is also the first butterfly fossil from the Early Pleistocene epoch, dating back between 2.6 million and 1.8 million years ago. The period was marked by major climatic and environmental changes, as global temperatures shifted from the Late Pliocene to the cooler Early Pleistocene.
The fossil was found in a slab of rock composed of tuffaceous siltstone, typical of the lithofacies of the Haruki Mudstone in the area. The preservation of the imprint, which includes a large butterfly wing and body, allowed researchers to confirm the species and add valuable information about the distribution of the genus Tacola.
The discovery expands the known range of the genus, extending its distribution in Southeast Asia and East Asia. Scientists suggest that Tacola kamitanii lived in a warm or temperate climate during the transition of the Japanese islands from the subtropical climate of the Late Pliocene to the cooler Early Pleistocene.
The research team, which included Hiroaki Aiba, Yui Takahashi, and Kotaro Saito, emphasized the importance of re-examining historical fossils to uncover new information about past biodiversity. The study contributes to the field of insect paleontology, shedding light on the evolution and distribution of butterflies.
The genus Tacola currently includes seven genera and over 170 species, predominantly distributed in the tropics. The discovery of Tacola kamitanii indicates that these butterflies were widely spread in Southeast and East Asia during the Late Pliocene to Early Pleistocene, enriching our understanding of historical biodiversity patterns.
While Tacola kamitanii had a wingspan of nearly 9 centimeters, the world's largest butterfly remains the Queen Alexandra's birdwing, still extant today, with a wingspan that can reach 25-28 centimeters.
The article was written with the assistance of a news analysis system.