Okurodani Formation

Okurodani Formation
Okurodani Formation
Stratigraphic range: Hauterivian–Aptian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Tetori Group
Underlies	Amagodani Formation
Overlies	Otaniyama Formation
Lithology
Primary	Mudstone, Siltstone, Sandstone
Other	Tuffite
Location
Region	Gifu Prefecture
Country	Japan

Last updated October 03, 2025

The Okurodani Formation is an Early Cretaceous geologic formation in central Honshu, Japan. Part of the Tetori Group, it primarily consists of freshwater continental sediments deposited in a floodplain environment, with occasional volcanic tuffite horizons. It has an uncertain age, probably dating between the Hauterivian and Aptian.^[1] An indeterminate iguanodontian dinosaur tooth has been recovered from the formation. Many other fossil vertebrates are known from the KO2 locality^[2]

Vertebrate Paleobiota

Amphibians

Amphibians reported from the Okurodani Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Anura	Indeterminate	KO2			Discoglossid grade
Caudata	Indeterminate	KO2

Squamates

Squamates reported from the Okurodani Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Sakurasaurus ^[3]	S. shokawensis	KO2
?Anguimorpha	Indeterminate	KO2
Scincomorpha	Indeterminate	KO2			new taxon
Squamata	Indeterminate	KO2			2 distinct taxa

Turtles

Turtles reported from the Okurodani Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
cf. Sinemys	Indeterminate	KO2
Sinochelys	Indeterminate	KO2			Sinochelyidae
Adocidae	Indeterminate	KO2
Trionychidae	Indeterminate	KO2

Choristoderes

Choristoderes reported from the Okurodani Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Monjurosuchus	Indeterminate	KO2		"Association of right squamosal, jugal, quadratojugal, and quadrate"		Monjurosuchus Shokawa ikoi
Shokawa	S. ikoi	KO2		Partial skeleton

Footnotes

↑ Amiot, Romain; Kusuhashi, Nao; Saegusa, Haruo; Shibata, Masateru; Ikegami, Naoki; Shimojima, Shizuo; Sonoda, Teppei; Fourel, François; Ikeda, Tadahiro; Lécuyer, Christophe; Philippe, Marc; Wang, Xu (2021-01-01). "Paleoclimate and ecology of Cretaceous continental ecosystems of Japan inferred from the stable oxygen and carbon isotope compositions of vertebrate bioapatite" (PDF). Journal of Asian Earth Sciences. 205 104602. Bibcode:2021JAESc.20504602A. doi: 10.1016/j.jseaes.2020.104602 . ISSN 1367-9120.
↑ "KO2 locality, Shokawa Village, Kobudani Valley (Cretaceous to of Japan)". Paleobiology Database.
↑ Evans, Susan E.; Manabe, Makoto (January 1999). "Early Cretaceous Lizards from the Okurodani Formation of Japan". Geobios. 32 (6): 889–899. Bibcode:1999Geobi..32..889E. doi:10.1016/s0016-6995(99)80871-7. ISSN 0016-6995.

References

Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.

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[1] Amiot, Romain; Kusuhashi, Nao; Saegusa, Haruo; Shibata, Masateru; Ikegami, Naoki; Shimojima, Shizuo; Sonoda, Teppei; Fourel, François; Ikeda, Tadahiro; Lécuyer, Christophe; Philippe, Marc; Wang, Xu (2021-01-01). "Paleoclimate and ecology of Cretaceous continental ecosystems of Japan inferred from the stable oxygen and carbon isotope compositions of vertebrate bioapatite" (PDF). Journal of Asian Earth Sciences. 205 104602. Bibcode:2021JAESc.20504602A. doi: 10.1016/j.jseaes.2020.104602 . ISSN 1367-9120.

[2] "KO2 locality, Shokawa Village, Kobudani Valley (Cretaceous to of Japan)". Paleobiology Database.

[3] Evans, Susan E.; Manabe, Makoto (January 1999). "Early Cretaceous Lizards from the Okurodani Formation of Japan". Geobios. 32 (6): 889–899. Bibcode:1999Geobi..32..889E. doi:10.1016/s0016-6995(99)80871-7. ISSN 0016-6995.

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