Yamatosaurus: New Duckbilled Dinosaur Discovered in Japan

Yamatosaurus izanagii

This artist’s illustration of Yamatosaurus izanagii (center) represents its ancestry to more advanced hadrosaurs (in the background). Credit: Artwork by Masato Hattori

An international team of paleontologists has identified a new genus and species of hadrosaur or duck-billed dinosaur, Yamatosaurus izanagii, on one of Japan’s southern islands.

The fossilized discovery yields new information about hadrosaur migration, suggesting that the herbivores migrated from Asia to North America instead of vice versa. The discovery also illustrates an evolutionary step as the giant creatures evolved from walking upright to walking on all fours. Most of all, the discovery provides new information and asks new questions about dinosaurs in Japan.

The research, “A New Basal Hadrosaurid (Dinosauria: Ornithischia) From the latest Cretaceous Kita-ama Formation in Japan implies the origin of Hadrosaurids,” was recently published in Scientific Reports. Authors include Yoshitsugu Kobayashi of Hokkaido University Museum, Ryuji Takasaki of Okayama University of Science, Katsuhiro Kubota of Museum of Nature and Human Activities, Hyogo and Anthony R. Fiorillo of Southern Methodist University.

Hadrosaurs, known for their broad, flattened snouts, are the most commonly found of all dinosaurs. The plant-eating dinosaurs lived in the Late Cretaceous period more than 65 million years ago and their fossilized remains have been found in North America, Europe, Africa, and Asia. 

Yamatosaurus Dentary

The right dentary of Yamatosaurus izanagii distinguishes it from other known hadrosaurs. It has just one functional tooth in several battery positions and no branched ridges on the chewing surfaces, suggesting that it evolved to devour different types of vegetation than other hadrosaurs. Credit: Southern Methodist University

Yamatosaurus Locality

This map of Japan shows the locations of Yamatosaurus izanagii on Awaji Island (green star) and Kamuysaurus in Mukawa Town (blue star). The locations of other hadrosaurids found on Awaji Island are marked with the red star. In the stratigraphic sections, the location of Yamatosaurus izanagii is marked with a green star and the location of Kamuysaurus is marked with a blue star. Credit: Southern Methodist University

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