AsianScientist (Sep. 18, 2019) – A new species of duck-billed dinosaur has been unearthed from 72 million-year-old marine deposits in Mukawa Town, northern Japan. The findings are published in Scientific Reports.
A partial tail of the dinosaur was first discovered in the outer shelf deposits of the Upper Cretaceous Hakobuchi Formation in the Hobetsu district of Mukawa Town, Hokkaido, Japan in 2013. Ensuing excavations found a nearly complete skeleton that is the largest dinosaur skeleton ever found in Japan.
The specimen was called ‘Mukawaryu,’ after the excavation site where it was discovered, but has been officially named Kamuysaurus japonicus, or the deity of Japanese dinosaurs.
In this study, a group of researchers led by Professor Yoshitsugu Kobayashi of the Hokkaido University Museum, Japan, conducted comparative and phylogenetic analyses on 350 bones and 70 taxa of hadrosaurids. They found that the K. japonicus belongs to the Edmontosaurini clade, and is closely related to Kerberosaurus, unearthed in Russia, and Laiyangosaurus, found in China.
The researchers also reported that K. japonicus has three unique characteristics that are not shared by other dinosaurs in the Edmontosaurini clade: the low position of the cranial bone notch, the short ascending process of the jaw bone and the anterior inclination of the neural spines of the sixth to twelfth dorsal vertebrae.
According to the team’s histological study, the dinosaur was an adult aged nine or older, measured eight meters long and weighed between 4-5.3 tons when it was alive. The frontal bone, a part of its skull, has a big articular facet connecting to the nasal bone, suggesting the dinosaur may have had a crest. The crest, if it existed, is believed to resemble the thin, flat crest of Brachylophosaurus subadults, whose fossils have been unearthed in North America.
The study also shed light on the origin of the Edmontosaurini clade and how it might have migrated. Its latest common ancestors spread widely across Asia and North America, which were connected by what is now Alaska, allowing them to travel between the two continents. Among them, the clade of Kamuysaurus, Kerberosaurus and Laiyangosaurus inhabited the Far East during the Campanian, the fifth of six ages of the Late Cretaceous epoch, before evolving independently.
The research team’s analyses pointed to the possibility that ancestors of hadrosaurids preferred to inhabit areas near the ocean. This suggests that the coastline environment was an important factor in the diversification of the hadrosaurids in their early evolution, especially in North America.
The article can be found at: Kobayashi et al. (2019) A New Hadrosaurine (Dinosauria: Hadrosauridae) from the Marine Deposits of the Late Cretaceous Hakobuchi Formation, Yezo Group, Japan.
———
Source: Hokkaido University; Photo: Hokkaido University.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
