Butterfly fossil in Japan breaks a world record

A butterfly wing fossil^*1 in Japan has set a world record. It is the oldest fossil in the world of a butterfly species^*2 that is still alive today. The fossil is about 2.5 million^*3 years old. Keio University, a university in Tokyo, the capital of Japan, announced the news on October 13.

The fossil is a front wing about 42 millimeters long. It came from the rock of an old lake in Shin'onsen, a town in Hyogo, a prefecture^*4 in western Japan. About 35 years ago, Masao Baba, a worker at the town office, found it while he was studying the land there. He gave it to the Insect Fossil Museum in the town. The museum is run by the town's board of education^*5, and the fossil has been on show there since then.

A research team studied the wing. Yui Takahashi, a teacher at Keio Yochisha, the elementary school of Keio, led the team. Hiroaki Aiba of Keio and Kotaro Saito of the Research Institute of Evolutionary Biology and the company Koyo Seiki were also on the team. They compared the wing with the wings of about 40 living species in one group of white butterflies. The wing matched one species, Aporia potanini^*6. This butterfly does not live in Japan today. It lives only in northern and northeastern China.

Before this, the oldest fossil of a living butterfly species was about 300,000 years old. That fossil was a different kind of butterfly. It was found in Nasushiobara, a city in Tochigi, a prefecture in eastern Japan. The new fossil is much older. The team's paper^*7 was published online on July 29 in the Journal of Paleontology, a science magazine.

1. *1 fossil: the remains of a plant or animal that lived long ago, kept in rock
2. *2 species: one kind of animal or plant
3. *3 million: 1,000,000
4. *4 prefecture: a large area of Japan with its own local government, like a state
5. *5 board of education: the office of a town or city that looks after its schools and museums
6. *6 Aporia potanini: the science name of one kind of white butterfly
7. *7 paper: a report in which scientists write what they found