蝶の化石の発見
Today's episode, Time Capture Open Secrets of the World's Largest Butterfly from 2.5
Million Years Ago Found in Japan. Welcome to SCIEN-SPOT, this podcast shines the spotlight
on the latest in science and technology from Japan. I am your host, REN from SCIEN-TALK.
Today on SCIEN-SPOT, I bring you news of an amazing discovery as if a time capsule from
across ages has been opened. Believe it or not, the world's largest butterfly fossil
has been found in Japan. And it's from a geological layer approximately 2.5 million years old.
What kind of butterfly could this have been? First, to understand the significance of today's
discovery, let's talk about how rare butterfly fossils are. While we find fossils of various
organisms on Earth, insect fossils are generally harder to find compared to plant or shell fossils,
and among insect fossils, butterfly fossils are considered extremely rare.
Why are butterfly fossils uncommon? There are several reasons. First,
butterflies are very light, and their wings are covered in fine scales. Because of this,
even after they die, they tend not to sink in water. For something to become a fossil,
it often needs to be quickly buried in water and sediment, so this is a major handicap.
Even if they do sink, butterflies have soft bodies. They can be eaten by fish or other creatures,
250万年前の蝶の化石発見
or simply decay, making it difficult for their form to be preserved.
In other words, for a butterfly to become a fossil in the den for a human to discover
is truly a miraculous event. It's said that only about 60 adult butterfly fossils have been
reported worldwide. Of course, about 40 species have been named. What's more, over half of these
are old discoveries from the 19th century. In the 21st century, since the year 2000,
only a few discoveries have been reported, including the one today. Just hearing these
numbers gives you an idea of how precious this discovery is. So when, where, and by whom
was this discovery and the butterfly fossil found? This fossil was discovered 37 years ago,
1988, in a geological layer about 2.5 million years old in the Hyogo Prefecture.
This discovery was made by the late Mr. Kamitani, a local high school teacher. Mr. Kamitani had
kept this valuable fossil at the local museum, the Omoshiro Insect Fossil Museum.
Omoshiro means interesting in English. And for a long time after its discovery,
basic research was conducted, but it remained a bizarre fossil scientific description. However,
Mr. Hiroaki Iver and Ms. Yui Takahashi from Keio University became aware of this specimen and
decided to conduct further research. It's possible that capturing the detailed structure
カミタニミツジの発見
of the fossil was difficult with microscopes 37 years ago. But thanks to recent high-resolution
microscope technology, very detailed morphological features, such as on wings, veins, and where
they were developed, researchers at Keio University and experts in butterfly classification
joined the research team and professional analysis proceeded. As a result, it was proven that the
fossil is a completely new species belonging to the genus Onimitsuji of the family
and brush-footed butterflies. In honor of this discoverer, Mr. Kamitani, the new species was
named Kamitani-mitsuji. And regarding the condition of the fossil, the head was not preserved,
but many parts, including the thorax, forewings, and head wings were relatively well preserved.
What makes the discovery of Kamitani-mitsuji so remarkable? First, its size. It's estimated that
the following length was 48 mm and the wingspan was an astonishing 84 mm. This makes it the largest
size among all butterfly fossils found worldwide to date. It is truly the world's largest butterfly
fossil. Furthermore, this fossil represents the first-ever fossil report for the genus Onimitsuji
worldwide. And there's another important point. This fossil was found in a geological layer from
蝶の化石発見の意義
approximately 2.5 million years ago. Most of the previously named butterfly fossils are from much
older periods, before the meal scene. Among this age of the butterfly fossils, only one from Japan,
about 3.5 million years old, was known with the name. And no name of the new species' fossils
from later periods were known. Therefore, Kamitani-mitsuji is a fossil species on an
extinct butterfly found from the most recent era worldwide. This provides extremely important
psychological data from considering the subsequent evolution of the butterflies.
Also, butterflies of the genus Onimitsuji do not currently inhabit Japan. Their relatives now live
in the subtropical to tropical regions of Southeast Asia. The fact that a gendered butterfly
similar to those now found in Southeast Asia inhabited Japan about 2.5 million years ago
suggested that Japan's climate and environment at that time were likely quite different from today.
Butterfly fossils in this way serve as a valuable window not only into the evolution of the organism
itself, but also for discussing the Earth's environment and the distribution of organisms
at that time. The small stone-like fossil discovered by the late Mr. Kamitani 37 years ago,
thanks to the latest research, has revealed the appearance of the world's largest butterfly that
驚くべき発見
lived on Earth approximately 2.5 million years ago. And giving us hints about the environment
at that time, it's truly a discovery that makes you feel the romance of science connecting the
past and the present. OK, that's it. SciencePod is delivered every weekday morning in Japanese
and English. I'd happy if you listen to the podcast and post your notes and thoughts with
the hashtag SciencePod. See you next time.
