Cranial fossils of a nodosaurid ankylosaur unearthed greater than 20 years in the past on the Japanese island of Hokkaido have been acknowledged as belonging to a brand new genus and species.
Nipponopelta yezoensis. Picture credit score: TotalDino / CC BY 4.0.
The newly recognized dinosaur species roamed Earth through the Late Cretaceous epoch, between 96 and 94 million years in the past.
Named Nipponopelta yezoensis, it’s the first ankylosaur ever formally named from Japan, and solely the second Asian member of its subfamily, the nodosaurids, identified from cranium materials reasonably than bones from the physique alone.
“The historically identified ankylosaurs (now Euankylosauria) are divided in two main clades, nodosaurids and ankylosaurids, among the many most generally found dinosaurs from Cretaceous deposits,” mentioned Hokkaido College paleontologist Shumpei Oyabu and his colleagues.
“The geographic distribution of nodosaurids, outlined by the most important clade containing Nodosaurus textilis however not Ankylosaurus magniventris, extends to 5 main continents, together with North America, South America, Asia, Europe, and Antarctica.”
“Importantly, nodosaurids are extra generally present in marine deposits in comparison with ankylosaurids.”
“This distribution sample could also be partially attributed to the restricted presence of ankylosaurids in North America.”
“However, a number of research counsel that nodosaurids have been extra tailored to coastal and estuarine environments.”
“In Asia, nodosaurids are primarily discovered within the mid-Cretaceous deposits in Japan and China. Their abundance is far smaller than that of North American and European nodosaurids.”
A partial cranium, a cranial vertebra and several other tooth from Nipponopelta yezoensis have been found within the 2000s in a concretion from the higher a part of the Hikagenosawa Formation in Yubari metropolis, Hokkaido, Japan.
The fossils have been initially recognized as a nodosaurid; nonetheless, its taxonomic standing remained unresolved.
Oyabu and co-authors from Japan, Canada and the USA revisited the specimens within the new examine.
Utilizing three-dimensional CT scanning, they was in a position to digitally reconstruct components of the cranium that had by no means been seen earlier than, together with a piece of the decrease jaw, two intact tooth, and, notably, the dinosaur’s left internal ear.
The scans additionally uncovered a particular mixture of options in the back of the cranium.
The crew’s phylogenetic evaluation signifies that Nipponopelta yezoensis is deeply nested amongst derived nodosaurids from North America and Europe, reminiscent of Pawpawsaurus, Panoplosaurus, Edmontonia and Denversaurus, reasonably than grouped with the handful of different nodosaurids beforehand described from Asia.
To clarify this sample, the paleontologists modeled how the dinosaur’s ancestors might need moved throughout the globe over tens of millions of years.
“Ancestral geographic evaluation means that Nipponopelta yezoensis and its shut kinfolk originated in Laramidia, Appalachia, and Asia, indicating a large ancestral space,” they mentioned.
The researchers additionally traced how ankylosaurs’ most well-liked habitats modified over time.
Their reconstruction means that these dinosaurs typically arose in coastal settings earlier than some branches moved inland, however that nodosaurids, and Nipponopelta yezoensis specifically, retained a choice for marine-influenced habitats.
“Habitat reconstruction reveals that Nipponopelta yezoensis most well-liked marine influenced environments, probably inhabiting coastal or estuarine areas,” the scientists mentioned.
“This choice for coastal environments performed a major function in its dispersal patterns throughout completely different areas.”
The invention of Nipponopelta yezoensis is described in a paper within the journal Cretaceous Analysis.
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S. Oyabu et al. A brand new nodosaurid ankylosaur (Dinosauria: Ornithischia) from the Higher Cretaceous Hikagenosawa Formation in Japan reveals dispersal sample of Asian nodosaurid ankylosaurs. Cretaceous Analysis, printed on-line August 21, 2026; doi: 10.1016/j.cretres.2026.106477
