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	36.2°N 136.7°E / 36.2; 136.7
Approximate paleocoordinates	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 Kappachelys^[3]

Fossil content

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

• Osteichthyes indet. - 'fish scales'

Reptiles

• Turtles
  • Kappachelys okurai^[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 indeterminate dinosaur fossils
  • List of stratigraphic units with ornithischian tracks
    • Ornithopod tracks

References

1. Akaiwa Formation in the Paleobiology Database
2. Weishampel et al., 2004, pp.517-607
3. Hirayama et al., 2013
4. Matsukawa & Obata, 1994
5. Matsumoto et al., 2014
6. Azuma & Tomida, 1995

Bibliography

• Matsumoto, R.; Manabe, M.; Evans, S. E. (2014), "The first record of a long-snouted chrositodere (Reptilia, Diapsida) from the Early Cretaceous of Isihikawa Prefecture, Japan", Historical Biology, 27: 583–594, doi:10.1080/08912963.2014.898296
• Hirayama, R.; Isaji, S.; Hibino, T. (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, Morphology and Evolution of Turtles, pp. 179–185
• Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (2004), The Dinosauria, 2nd edition, Berkeley: University of California Press, pp. 1–880, ISBN 0-520-24209-2, retrieved 2019-02-21
• Azuma, Y.; Tomida, Y. (1995), Early Cretaceous dinosaur fauna of the Tetori Group in Japan. In A. Sun, Y. Wang (eds.), Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers, pp. 125–131
• Matsukawa, M.; Obata, I. (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 (1): 101–125, Bibcode:1994CrRes..15..101M, doi:10.1006/cres.1994.1005