Open Paleo

Nipponopelta

Oyabu et al., 2026 NIP-on-o-PEL-tuh

From Japanese 'Nippon' (Japan) and Greek 'pelta' (shield); meaning 'Japanese shield'.

100.5–93.9 million years ago Cenomanian, Late Cretaceous
Late Cretaceous stages

Nipponopelta is an extinct genus of nodosaurid ankylosaurian dinosaur known from the Late Cretaceous (Cenomanian age) Hikagenosawa Formation of the Yezo Group in Japan. The genus contains a single species, Nipponopelta yezoensis, known from a partial skull and fragmentary associated remains. It is the first ankylosaur to be named from Japan.

Diagnosis

  1. Quadrate anterior surface is lateromedially concave, giving the quadrate an overall half-pipe shape.
  2. Paroccipital process bears a well-developed ridge forming a slightly horizontal shelf together with the supraoccipital.
  3. Paroccipital processes extend posterolaterally in ventral view.
  4. Lateral surface of the braincase bears a prominent, gently swollen ridge running anteroposteriorly.
  5. Maxillary and dentary tooth crown striations are not confluent with the denticles.
  6. Teeth have large crowns and sigmoid roots.
  7. Anterior margin of the neural arch of the atlas is concave.

Species

Nipponopelta yezoensis Oyabu et al., 2026

Type species

From Yezo, the traditional name for Hokkaido Island, where the specimen was discovered.

Holotype
MCM A522 , Mikasa City Museum
Material
Partial skull with a partial mandible, 11 associated teeth, a partial atlas, 11 free teeth, and 3 free osteoderms.
Horizon
upper Hikagenosawa Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Omakizawa River, Hokkaidō, Japan

References

  1. Oyabu, S.; Kobayashi, Y.; Zelenitsky, D. K.; Fiorillo, A. R.; Kano, M. (2026). A new nodosaurid ankylosaur (Dinosauria: Ornithischia) from the Upper Cretaceous Hikagenosawa Formation in Japan reveals dispersal pattern of Asian nodosaurid ankylosaurs. Cretaceous Research 106477. Elsevier BV. doi:10.1016/j.cretres.2026.106477 oyabu2026a
  2. Hayakawa, H.; Manabe, M.; Carpenter, K. (2005). Nodosaurid ankylosaur from the Cenomanian of Japan. Journal of Vertebrate Paleontology 25(1): 240-245. Informa UK Limited. doi:10.1671/0272-4634(2005)025[0240:NAFTCO]2.0.CO;2

    First description of the holotype, as an indeterminate nodosaurid, with the locality, stratigraphy and cranial and dental anatomy that the naming study built on.

    hayakawa2005a