A tiny relative of the Triceratops: International team discovers a new horned dinosaur

Carleton University's Michael Ryan is part of an international research team that has discovered a well-preserved fossil of a new horned dinosaur in Japan's Tambasasayama City, Hyogo Prefecture. Details have been published in the journal Papers in Palaeontology.

This new dinosaur possesses unique characteristics distinct from any known ceratopsian. Ceratopsians are a group of herbivorous dinosaurs known for their large horns and frills on their heads, the most famous being Triceratops.

As a primitive ceratopsian, it lacked the large horns and frills seen in later species like the Triceratops and its diminutive body length and mass are only approximately 80 cm and 10 kg, respectively. Additionally, its internal bone structure and growth rings indicate that it was still a young, growing individual when it died.

This new dinosaur has been named Sasayamagnomus saegusai, with the genus name meaning "a small humanoid spirit guarding hidden treasures under the ground of Sasayama," and the species name honoring the late Haruo Saegusa.

The fossil includes 17 bones, most of which belong to a single individual. Thin sections of the tibia were examined, revealing that Sasayamagnomus was likely a young, not fully matured individual.

Sasayamagnomus is closely related to primitive ceratopsians from North America, suggesting that ceratopsians, which originated in Asia, may have immigrated to North America around 110 million years ago during the mid-Cretaceous period.

During this period, the eastern part of the Eurasian continent and North America were connected by the Bering Land Bridge, allowing animals to migrate between the two. Additionally, extreme global warming resulted in vast forests in the Arctic region. The convergence of these two events likely facilitated the expansion of ceratopsians from Asia to North America.