FUKUI – A rock found in 1965 by a high school student in the city of Shimonoseki, Yamaguchi Prefecture, has been confirmed to be a dinosaur egg fossil, according to the city and the Fukui Prefectural Dinosaur Museum.
To date, eight types of dinosaur egg fossils have been discovered in Japan, in Fukui, Gifu and Hyogo prefectures.
The fossilized egg confirmed in Yamaguchi Prefecture, which was broken into pieces, is different from the other eight, and it is likely to be an egg laid by a bipedal carnivorous dinosaur, or theropod, the city and the museum said Monday.
The egg fossil has become the earliest known discovery of a dinosaur fossil in Japan, overtaking a fossil of the upper arm of a Moshiryu dinosaur found in the town of Iwaizumi, Iwate Prefecture in 1978.
The rock was collected by Yoshiharu Shimizu, a native of Shimonoseki, and a friend in September 1965, when Shimizu was a second-year high school student, according to the museum in the city of Katsuyama, Fukui Prefecture. They discovered it in a layer dating back to the early Cretaceous period, or between 120 million and 100 million years ago, in the upstream area of the Ayaragi river in Shimonoseki.
Shimizu, now a 68-year-old company employee in the city of Yokosuka, Kanagawa Prefecture, kept the rock pieces at his home, along with sketches and photos as well as the photo negatives.
After recalling the treasure trove, he asked a nephew, who is an employee of the municipal government of the city of Mine, Yamaguchi, in March last year to find out what they were.
The Fukui museum worked with entities including the Mine Fossil Museum to identify the rocks.
The eight pieces are 2 to 7 centimeters in diameter. After taking photos, Shimizu broke the rock into pieces with a hammer.
His sketches and other information suggest that the egg was either spherical or oval in shape, with an estimated diameter of about 10 centimeters.
The shell is about 3.7 millimeters thick, far exceeding the 0.1 to 0.7 measurement found in other dinosaur eggs discovered in Japan.
“Direct evidence that dinosaurs existed in the Chugoku region had not been discovered before,” said Takuya Imai, 29, a researcher from the Fukui museum who examined the fragments. “The discovery of the egg fossil shows that dinosaurs bred actively in the region in the early Cretaceous period.”
Yoichi Azuma, executive director of the museum, said the discovery “rewrote the history of dinosaur research.” He added that the sketches by Shimizu were very accurate.
The site where the rock was found and the date of its collection — important information used for verifying the authenticity of the discovery — were recorded on the sketches. Had it not been for that information, it would have been impossible to make an objective judgment that the egg represents the first dinosaur fossil discovery in Japan, according to Imai.
Noting that taking photos and drawing sketches are part of research, Azuma stressed that the latest development “could mark the start of dinosaur research in Japan.”
In a statement released Monday, Shimizu said: “My high school teacher taught me the importance of taking records. I believe this helped lead to the result.”
Shimonoseki Mayor Shintaro Maeda said the city wants “to share the joy with citizens, and send the news to dinosaur fans across Japan and throughout the world.”
Maeda underscored the city’s willingness to promote tourism by taking advantage of the news.