Hakobuchi Formation

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Hakobuchi Formation
Stratigraphic range: Early Maastrichtian
Type Geological formation
Unit of Yezo Group
Underlies Ishikari Group, Poronai Group
Overlies Haborogawa Formation, Kashima Formation
ThicknessOver 450 metres (1,480 ft)
Lithology
Primary Mudstone, Siltstone, Sandstone
Other Tuffite
Location
Region East Asia
CountryFlag of Japan.svg  Japan
Extent Hokkaido

The Hakobuchi Formation is a geological formation in Hokkaido, Japan. It is the uppermost unit of the Yezo Group, being early Maastrichtian in age. It consists of bioturbated glauconitic sandstones, siltstones and conglomerates with coaly mudstone and minor tuffite. It was deposited in a continental shelf setting. [1] It is noted for its fossil content with the invertebrates mainly consisting of bivalves and ammonites. With vertebrates including the mosasaurs Mosasaurus hobetsuensis and Phosphorosaurus ponpetelegans. [2] As well the sea turtle Mesodermochelys [3] and the hadrosaurid dinosaur Kamuysaurus . [4]

Contents

Fossil content

Color key
Taxon Reclassified taxonTaxon falsely reported as presentDubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Dinosaurs

Ornithopods

Ornithopods of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Kamuysaurus [5] K. japonicusA edmontosaurin saurolophine
Kamuysaurus japonicus.png

Mosasaurs

Mosasaurs of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Mosasaurus M. hobetsuensis A mosasaurine mosasaurid
Carcass of Kamuysaurus.jpg
Phosphorosaurus P. ponpetelegansA halisaurine mosasaurid
Phosphorosaurus ponpetelegans.jpg

Turtles

Turtles of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Mesodermochelys M. undulatusA dermochelyid turtle
Mesodernochelys at Hobetsu Museum in Mukawa, Hokkaido (cropped).jpg

Fish

Cartilaginous Fish

Cartilaginous Fish of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Callorhinchus [6] C. orientalis A callorhinchid chimaeran
Callorhinchus orientalis.png

Molluscs

Bivalves

Bivalves of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Inoceramus I. nipponicusA inoceramid bivalve

Cephalopods

Cephalopods of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Pachydiscus P. japonicusA pachydiscid ammonite
Pachydiscus japonicus.jpg

Gastropods

Gastropods of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages

Paleoflora

Plants of the Hakobuchi Formation
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Mukawastrobus M. satoiA cypress
Nilssonia N. yezoensisA cycad

References

  1. Takashima, Reishi; Kawabe, Fumihisa; Nishi, Hiroshi; Moriya, Kazuyoshi; Wani, Ryoji; Ando, Hisao (June 2004). "Geology and stratigraphy of forearc basin sediments in Hokkaido, Japan: Cretaceous environmental events on the north-west Pacific margin". Cretaceous Research. 25 (3): 365–390. doi:10.1016/j.cretres.2004.02.004. hdl: 2115/17182 .
  2. Konishi, Takuya; Caldwell, Michael W.; Nishimura, Tomohiro; Sakurai, Kazuhiko; Tanoue, Kyo (2016-10-02). "A new halisaurine mosasaur (Squamata: Halisaurinae) from Japan: the first record in the western Pacific realm and the first documented insights into binocular vision in mosasaurs". Journal of Systematic Palaeontology. 14 (10): 809–839. doi:10.1080/14772019.2015.1113447. ISSN   1477-2019.
  3. Hirayama R, Chitoku T. (1996). "Family Dermochelyidae (Superfamily Chelonioidea) from the Upper Cretaceous of North Japan". Transactions and proceedings of the Palaeontological Society of Japan. New series184: 597-622. online, retrieved 28 July 2008
  4. Sakurai, Kazuhiko; Sato, Tamaki; Chinzorig, Tsogtbaatar; Tanaka, Kohei; Fiorillo, Anthony R.; Chiba, Kentaro; Takasaki, Ryuji; Nishimura, Tomohiro; Kobayashi, Yoshitsugu (September 5, 2019). "A New Hadrosaurine (Dinosauria: Hadrosauridae) from the Marine Deposits of the Late Cretaceous Hakobuchi Formation, Yezo Group, Japan". Scientific Reports. 9 (1): 1–14. doi: 10.1038/s41598-019-48607-1 . PMC   6728324 . PMID   31488887.
  5. Yoshitsugu Kobayashi; Tomohiro Nishimura; Ryuji Takasaki; Kentaro Chiba; Anthony R. Fiorillo; Kohei Tanaka; Tsogtbaatar Chinzorig; Tamaki Sato; Kazuhiko Sakurai (2019). "A new hadrosaurine (Dinosauria: Hadrosauridae) from the marine deposits of the Late Cretaceous Hakobuchi Formation, Yezo Group, Japan". Scientific Reports. 9 (1): Article number 12389. Bibcode:2019NatSR...912389K. doi:10.1038/s41598-019-48607-1. PMC   6728324 . PMID   31488887.
  6. Ota, A.; Nishimura, T.; Kobayashi, Y.; Moriki, K. (2025). "Callorhinchus orientalis sp. nov., a new callorhinchid from the Upper Cretaceous Hakobuchi Formation, Yezo Group, Hokkaido, Japan". Paleontological Research. 29 (1): 54–63. doi: 10.2517/prpsj.240013 .