New hadrosaur from Japan sheds light on dinosaur diversity

The discovery of a previously unknown species of hadrosaur dinosaur from the Late Cretaceous Period is reported in Scientific Reports this week. The fossil, found in Japan, furthers our understanding of hadrosaur diversity in the Far East and hadrosaurid evolution during the Late Cretaceous Period (100.5-66 million years ago).

Hadrosaurs are among the most successful group of dinosaurs from the Late Cretaceous, and their fossils have been found in North America, South America, Asia, Europe and Antarctica.

Life reconstruction of Kamuysaurus japonicus gen. et sp. nov. with a carcass of a mosasaur, a sea turtle, and shells of ammonoids and bivalves on the beach. The individual of Kamuysaurus in the foreground is reconstructed based on the assumption of the presence of a supracranial crest, similar to a sub-adult form of Brachylophosaurus. The individual behind it is reconstructed without the crest. Credit: Scientific Reports; Kobayashi et al. (2019)

Yoshitsugu Kobayashi and colleagues discovered the new hadrosaur, which they have named Kamuysaurus japonicus in marine deposits of the Hakobuchi Formation in Hokkaido, Japan. Its discovery in a marine-influenced environment is rare for hadrosaurs and contributes to understanding of the diversity of hadrosaurids in these environments, the authors suggest.


At around eight metres long, the 72 million-year-old specimen is a middle-sized, fully grown hadrosaur. The authors report a number of unique features, including a small crest on the skull and a short row of neural spines that point forwards. Analysis of this specimen suggests it is related to other hadrosaurs from the Far East such as Laiyangosaurus from China and Kerberosaurus from Russia.

Carcass of Kamuysaurus, foating in the sea, with two mosasaurs, two sea turtles, and four ammonoids. Credit: Scientific Reports; Kobayashi et al. (2019)