Dinosaur fossil identified as Japan’s largest ornithopod

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NAGASAKI–Researchers have determined that a fossil found in the layers of a local beach is the shoulder blade of a 9-meter-long ornithopod dinosaur, one of the largest in Japan and possibly a new species.

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The Nagasaki prefectural board of education and the Fukui Prefectural Dinosaur Museum, which have been conducting archaeological research together since fiscal 2012, released their latest findings on July 12.

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The shoulder blade fossil was discovered in May 2016 in a layer of earth from the late Cretaceous Period on the west coast of Nagasaki Peninsula in the city of Nagasaki.

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The stratum of earth, known as Mitsuse-so, is approximately 81 million years old.

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Heavy machinery was used to excavate the fossil a year after it was discovered.

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The repair and restoration work began in 2018 and was completed recently.

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Kazunori Miyata, the museum’s chief researcher, said the discovery is an invaluable piece of material in the study of the “ecology of dinosaurs living in groups in Nagasaki in the late Cretaceous Period.”

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The fossil is 90 centimeters long and 20 cm wide, and curves gently along the dinosaur’s thorax. The fossil is in near-perfect condition.

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Researchers concluded that the bone is a left-side shoulder blade from an advanced Hadrosauroidea based on its shape and length, among other factors.

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The Hadrosauroidea was a bipedal herbivore, a typical ornithopod that lived in the Cretaceous period.

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The oldest Hadrosauroidea fossil in Japan is one from a Koshisaurus discovered in Katsuyama, Fukui Prefecture, estimated to be approximately 120 million years old.

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Other late-Cretaceous Period discoveries in Japan are a 72-million-year-old Kamuysaurus fossil in Hokkaido and a Yamatosaurus fossil dug up on Awajishima island in Hyogo Prefecture that measures about 7-8 meters in length.

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Fossils from a large Tyrannosaurus and small theropod dinosaurs have also been discovered in the Mitsuse-so stratum.

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A replica of the new fossil discovery will be displayed at Nagasaki city hall, the museum in Fukui, and in other places, starting from July 16.

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