''Yamatosaurus'' (meaning "

Yamato was originally the area around today's Sakurai, Nara, Sakurai City in Nara Prefecture of Japan, which became Yamato Province and by extension a Names of Japan, name for the whole of Japan. Yamato is also the dynastic name of the ruling Imperial ...

reptile") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of basal

hadrosaurid Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

(

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

)-aged Kita-Ama Formation of Awaji Island,

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. The genus contains a single

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, ''Yamatosaurus izanagii''.

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

MNHAH D1-033516, consisting of part of the right lower

jaw The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth ...

, twelve

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

, four

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

, three cervical ribs, a partial right

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

and a posterior caudal vertebra, was discovered on Awaji Island in

in May 2004 by Shingo Kishimoto. In 2005, the find was reported in the scientific literature.Suzuki, D., Saegusa, H. & Furutani, H. 2005. "Newly found hadrosaur fossil co-producing broadleaf fossils from Sumoto, west central Japan". ''Journal of Vertebrate Paleontology'' 25: 120A Kishimoto in 2013 donated the holotype to Japan's Museum of Nature and Human Activities in the Hyogo Prefecture, where the fossils were prepared by Kazumi Wada, Tomomi Ikeda and Chisato Ota to be described in 2021. The species ''Yamatosaurus izanagii'' was named in 2021 by Yoshitsugu Kobayashi, Ryuji Takasaki, Katsuhiro Kubota and Anthony Ricardo Fiorillo. The fossils were found in dark grey

mudstones Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York ...

within the upper part Kita-Ama Formation, which was deposited in marine conditions in distal

turbidite A turbidite is the geologic Deposition (geology), deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing ...

facies on the edge of the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

in an intra-arc basin. The sediments date to subchron 32.1r28, corresponding to the early

stage of the Late Cretaceous, around 71.94–71.69 million years ago, making it roughly contemporaneous with fellow Japanese hadrosaur '' Kamuysaurus.'' Yamatosaurus izanagii restoration

Etymology

The generic name, ''Yamatosaurus'', refers to

Yamatai Yamatai or Yamatai-koku is the Sino-Japanese name of an ancient country in Wa (Japan) during the late Yayoi period The Chinese text ''Records of the Three Kingdoms'' first recorded the name as ()Schuessler, Axel (2014). "Phonological Notes ...

, also known as Yamato, an ancient region in Japan ruled by the Yamato Kingdom, while the specific name, ''Y. izanagii'', refers to the deity

Izanagi Izanagi (イザナギ/伊邪那岐/伊弉諾) or Izanaki (イザナキ), formally referred to with a divine honorific as , is the creator deity (''kami'') of both creation and life in Japanese mythology. He and his sister-wife Izanami are the ...

, who created eight islands in Yamato: Awaji Island (where the holotype was discovered)

Shikoku is the smallest of the List of islands of Japan#Main islands, four main islands of Japan. It is long and between at its widest. It has a population of 3.8 million, the least populated of Japan's four main islands. It is south of Honshu ...

, Oki,

Kyushu is the third-largest island of Japan's Japanese archipelago, four main islands and the most southerly of the four largest islands (i.e. excluding Okinawa Island, Okinawa and the other Ryukyu Islands, Ryukyu (''Nansei'') Ryukyu Islands, Islands ...

Iki IKI may refer to: * Internationales Kulturinstitut, in Vienna * Iodine potassium-iodide, a chemical compound * Russian Space Research Institute, originally known as IKI RAN * Iki Airport, IATA code Iki or iki may refer to: * Iki Island, a Japane ...

, Tsushima, Sado and

Honshu , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...

Classification

''Yamatosaurus'' is a basal hadrosaurid, more derived than ''Hadrosaurus'' but less than

Saurolophinae Saurolophinae is a subfamily (biology), subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. How ...

Lambeosaurinae Lambeosauridae /ˌlæmbiəˈsɔːraɪniː/ (meaning 'lambe's lizards') is an extinct group of crested hadrosauroid dinosaurs. Description Size Uncertainty surrounds the size of lambeosaurs from the European continent. Hadrosaurs found there, ...

. Its presence, along with those of '' Plesiohadros'' and '' Tanius'', suggests East Asia may have served as a refuge for basal hadrosaurs in the Late Cretaceous. However, it was also contemporaneous with the more derived ''Kamuysaurus'', suggesting some level of provinciality.

References

{{Taxonbar, from=Q106632486 Hadrosauridae Dinosaur genera Maastrichtian dinosaurs Dinosaurs of Japan Fossil taxa described in 2021 Taxa named by Anthony Fiorillo