A research group led by Professor Yoshitsugu Kobayashi of the Hokkaido University Museum is a primitive dinosaur fossil discovered in the late Hadrosaurid (about 2004 million years ago) strata in Sumoto City, southern Awaji Island, Hyogo Prefecture. It was named "Yamatosaurus Izanagii" because it belongs to the family Hadrosauridae.Other participants in the research group are Okayama University of Science, Museum of Nature and Human Activities, Hyogo Prefecture, and Southern Methodist University in the United States.
Hadrosaurid dinosaurs are the most successful herbivorous dinosaurs of the Cretaceous, with long, flat, duck-like beaks on their snouts.The fossil of Sumoto City (a part of the lower jaw) was discovered by Shingo Kishimoto (resident in Himeji City).In the joint research at that time, it was designated as the Lambeosaurinae, which was derived from the Hadrosauridae.
This time, it was identified as a new genus and new species of dinosaurs because this fossil has tooth characteristics not found in other Late Cretaceous Hadrosauridae.It was named "Yamatosaurus Izanagii" from "Yamato", which indicates the ancient Japanese nation, and "Izanagi", the male god that appears in Japanese mythology.
The research group suggested that the Hadrosauridae originated in Asia and the eastern part of the United States (Appalachian Mountains), and then prospered in Asia. He also points out the importance of forelimb evolution.
He also proposed that Yamatosaurus may have inhabited about 2 million years before the discovered strata.East Asia at that time may have been a region (refugium) where the pristine species remained for 2 to 3 million years for the primitive Hadrosauridae.Also, in the latter half of the Cretaceous, an evolved Kamuysaurus (named 2019) appeared in the Hadrosauridae family in Hokkaido, but Yamatosaurus may have survived until the end of the Cretaceous by segregating locally with Kamuysaurus. ..
Paper information:[Scientific Reports] A new basal hadrosaurid (Dinosauria: Ornithischia) from the latest Cretaceous Kita-AmaFormation in Japan implies the origin of hadrosaurids
