Akaiwa Formation

Akaiwa Formation Stratigraphic range: Hauterivian-Barremian ~132–125 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Tetori Group
Underlies	Kitadani Formation
Overlies	Kuwajima Formation
Lithology
Primary	Sandstone, conglomerate
Location
Coordinates	36°12′N 136°42′E / 36.2°N 136.7°E / 36.2; 136.7Coordinates: 36°12′N 136°42′E / 36.2°N 136.7°E / 36.2; 136.7
Approximate paleocoordinates	46°06′N 138°18′E / 46.1°N 138.3°E / 46.1; 138.3
Region	Honshu
Country	Japan
Akaiwa Formation (Japan)

The Akaiwa Formation (Japanese: 赤岩層, romanized: Akaiwa-sō) is an Early Cretaceous (Hauterivian-Barremian) geologic formation in central Honshu, Japan.^[1] Indeterminate ornithischian fossils are known from the formation. Fossil ornithopod tracks have been reported from the formation.^[2] As well as the turtle ^[3]

Fossil content[]

The following fossils have been reported from the formation:^[1]

• Osteichthyes indet. - 'fish scales'

Reptiles

• Turtles
  • ^[3]
• Crocodylomorpha indet. - isolated teeth of small crocodiles^[4]
• ?Euornithopoda indet.
• Neochoristodera indet. - a nearly complete right premaxilla^[5]
• Ornithopoda indet. - isolated teeth of small ornithopods
• ?Theropoda indet.

Ichnofossils

• Ornithischia indet. - tracks^[6]

See also[]

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with ornithischian tracks
    • Ornithopod tracks

References[]

Bibliography[]

• Matsumoto, R.; M. Manabe, and S. E. Evans. 2014. The first record of a long-snouted chrositodere (Reptilia, Diapsida) from the Early Cretaceous of Isihikawa Prefecture, Japan. Historical Biology 27. 583–594.
• Hirayama, R.; S. Isaji, and T. Hibino. 2013. Kappachelys okurai gen. et sp. nov., a new stem soft-shelled turtle from the Early Cretaceous of Japan. In D. B. Brinkman, P. A. Holroyd, J. D. Gardner (eds.), 179–185. Morphology and Evolution of Turtles.
• Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2
• Azuma, Y., and Y. Tomida. 1995. Early Cretaceous dinosaur fauna of the Tetori Group in Japan. In A. Sun, Y. Wang (eds.), 125–131. Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers.
• Matsukawa, M., and I. Obata. 1994. Dinosaurs and sedimentary environments in the Japanese Cretaceous: a contribution to dinosaur facies in Asia based on molluscan palaeontology and stratigraphy. Cretaceous Research 15. 101–125.