Koshikibaatar, new multituberculate from Upper Cretaceous of Japan
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Ben Creisler
Apr 29, 2026, 1:59:15 PM (5 days ago) Apr 29
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Ben Creisler
A new paper:
Koshikibaatar kashimaensis gen. et sp. nov.
Takuma Sera, Nao Kusuhashi, Toshifumi Komatsu, Yuka Miyake, Daisuke Yamashita & Sota Niiyama (2026)
A new multituberculate mammal from the Upper Cretaceous Himenoura Group, southwestern Japan
Journal of Vertebrate Paleontology e2647846
doi: https://doi.org/10.1080/02724634.2026.2647846
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2647846
Multituberculates were one of the most successful mammalian groups during the late Mesozoic. However, due to taxonomic and temporal gaps in the successive fossil record, the origin and early evolutionary history of Cimolodonta in the Late Cretaceous of Asia remain unclear. To address these issues, further discoveries of multituberculates, particularly from regions outside of Mongolia, are essential. We here describe a new cimolodontan multituberculate, Koshikibaatar kashimaensis gen. et sp. nov., from the middle Campanian Himenoura Group in Kagoshima Prefecture, southwestern Japan. This new species is characterized by dentary showing a low difference in height between the mandibular body below p3 and below m1, lower dental formula 1.0.2.2, slender lower incisor completely covered with enamel, single-rooted and peg-like p3, arcuate and triple-rooted p4 with 12 serrations, which has a weak protrusion of the mesial margin and a nearly symmetrical dorsal arch in lateral view and is higher than the occlusal level of molars, and m1 with cusp formula 5:3. These characteristics are obviously different from those of derived cimolodontans from the Upper Cretaceous of Asia, especially Mongolia, and suggest that the new species represents a relatively plesiomorphic cimolodontan multituberculate. The discovery of Koshikibaatar implies that the taxonomic diversity of Asian multituberculates during the Late Cretaceous was likely more diverse than previously recognized.
Koshikibaatar kashimaensis gen. et sp. nov.
Takuma Sera, Nao Kusuhashi, Toshifumi Komatsu, Yuka Miyake, Daisuke Yamashita & Sota Niiyama (2026)
A new multituberculate mammal from the Upper Cretaceous Himenoura Group, southwestern Japan
Journal of Vertebrate Paleontology e2647846
doi: https://doi.org/10.1080/02724634.2026.2647846
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2647846
Multituberculates were one of the most successful mammalian groups during the late Mesozoic. However, due to taxonomic and temporal gaps in the successive fossil record, the origin and early evolutionary history of Cimolodonta in the Late Cretaceous of Asia remain unclear. To address these issues, further discoveries of multituberculates, particularly from regions outside of Mongolia, are essential. We here describe a new cimolodontan multituberculate, Koshikibaatar kashimaensis gen. et sp. nov., from the middle Campanian Himenoura Group in Kagoshima Prefecture, southwestern Japan. This new species is characterized by dentary showing a low difference in height between the mandibular body below p3 and below m1, lower dental formula 1.0.2.2, slender lower incisor completely covered with enamel, single-rooted and peg-like p3, arcuate and triple-rooted p4 with 12 serrations, which has a weak protrusion of the mesial margin and a nearly symmetrical dorsal arch in lateral view and is higher than the occlusal level of molars, and m1 with cusp formula 5:3. These characteristics are obviously different from those of derived cimolodontans from the Upper Cretaceous of Asia, especially Mongolia, and suggest that the new species represents a relatively plesiomorphic cimolodontan multituberculate. The discovery of Koshikibaatar implies that the taxonomic diversity of Asian multituberculates during the Late Cretaceous was likely more diverse than previously recognized.
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