Open Paleo

Yamatosaurus

Kobayashi et al., 2021 yah-MAH-toh-SAWR-us

Named after Yamato, an ancient name for Japan, combined with Greek sauros meaning 'lizard' (or Latin saurus); translates as 'Yamato reptile'

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Yamatosaurus is a genus of basal hadrosaurid from the Late Cretaceous (Maastrichtian)-aged Kita-Ama Formation of Awaji Island, Japan. The genus contains a single species, Yamatosaurus izanagii.

Diagnosis

  1. Dentary teeth with crown-root angle between 110-130 degrees
  2. Low angle between dentary symphysis and lateral surface of dentary
  3. Ventrally facing ventral surface of surangular
  4. Single functional tooth per tooth position in middle dental battery (unique among Eolambia and higher taxa)
  5. Complete absence of branched ridges on dentary tooth occlusal surfaces

Species

Yamatosaurus izanagii Kobayashi et al., 2021

Type species

Named for Izanagi, the Shinto deity who, according to Japanese mythology, created eight islands including Awaji Island, where the holotype was discovered.

Holotype
MNHAH D1-033516 , Museum of Nature and Human Activities
Material
Right dentary, right surangular, isolated dentary teeth, cervical vertebrae, caudal vertebra, cervical ribs, and coracoid
Horizon
upper Kita-ama Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Aw14, Yura Town, Hyōgo, Japan

References

  1. Kobayashi, Y.; Takasaki, R.; Kubota, K.; Fiorillo, A. R. (2021). A new basal hadrosaurid (Dinosauria: Ornithischia) from the latest Cretaceous Kita-ama Formation in Japan implies the origin of hadrosaurids. Scientific Reports 11(1). Springer Science and Business Media LLC. doi:10.1038/s41598-021-87719-5 kobayashi2021a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a