Morawan (Upper tuffaceous Siltstone Member): Chattian, Japan

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Osteichthyes - Cetacea - Squalodontidae
Oishi and Hasegawa 1995 1 specimen
this specimen is from the Morawan Fm., member unknown
Osteichthyes - Cetacea - Aetiocetidae
1 specimen
1 specimen
Sawamura 2008 1 specimen
AMP 14
Marx and Fordyce 2015
Tsai and Ando 2015 1 specimen
AMP 9
Osteichthyes - Perissodactyla
Inuzuka 2000 1 specimen
see common names

Geography
Country:Japan State/province:Hokkaido
Coordinates: 43.3° North, 143.8° East (view map)
Paleocoordinates:44.9° North, 140.2° East (Wright 2013)
Basis of coordinate:estimated from map
Time
Period: Paleogene Epoch: Oligocene
Stage: Chattian 10 m.y. bin: Cenozoic 4
Key time interval: Chattian
Age range of interval: 27.3 - 23.04 m.y. ago
Age estimate: 26.1 to 23.3 Ma (other)
Stratigraphy
Geological group:Kawakami Formation:Morawan Member:Upper tuffaceous silstone
Stratigraphic resolution:member
Stratigraphy comments: Biostratigraphy indicates a mid-Rupelian age for the lowermost (Lower Hard Shale) member of the Morawan Formation [33, 34], as well as an earliest Chattian age for the bottom of the overlying Kiroro Formation [35, 36]. Together, these estimates constrain the age of A. polydentatus to the latest Rupelian or earliest Chattian. However, this is difficult to reconcile with markedly younger radiometric estimates, which suggest an age of 23.3 ± 0.7 Ma for the bottom of the Kiroro Formation, 28.6 ± 0.7 Ma for the Honbetsuzawa Formation underlying the Morawan Formation, and 26.1 ± 0.7 Ma for the upper part of the Middle Hard Shale Member of the Morawan Formation, which underlies the UTS [37, 38]. Until further data are available to resolve this issue, the age of A. polydentatus is therefore here assumed to be 26.1–23.3 Ma (early–late Chattian). (Marx & Fordyce, 2015)
Lithology and environment
Primary lithology: siltstone
Includes fossils?Y
Environment:basinal (siliceous)
Geology comments: basinal (siliceous), near shore
Taphonomy
Modes of preservation:body,original phosphate
Size of fossils:macrofossils
Preservation of anatomical detail:good
Collection methods and comments
Collection methods:surface (float),field collection
Reason for describing collection:taxonomic analysis
Metadata
Database number:45786
Authorizer:M. Uhen Enterer:M. Uhen
Modifier:B. Shipps Research group:vertebrate
Created:2004-12-01 11:48:46 Last modified:2025-02-22 15:12:02
Access level:the public Released:2004-12-01 11:48:46
Creative Commons license:CC0
Reference information

Primary reference:
12130. L. G. Barnes, M. Kimura, H. Furusawa and H. Sawamura. 1995. Classification and distribution of Oligocene Aetiocetidae (Mammalia; Cetacea; Mysticeti) from western North America and Japan. The Island Arc 3(4):392-431 [M. Uhen/M. Uhen/M. Uhen]

Secondary references:

16701 N. Inuzuka. 2000. Primitive late Oligocene desmostylians from Japan and Phylogeny of the Desmostylia. Bulletin of the Ashoro Museum of Paleontology 1:91-123 [M. Uhen/M. Uhen]
33201 H. Kurita. 2004. Paleogene Dinoflagellate Cyst Biostratigraphy of Northern Japan. Micropaleontology 50:1-50 [M. Uhen/S. Strother/M. Uhen]
55050 F. G. Marx and R. E. Fordyce. 2015. Baleen boom and bust: a synthesis of mysticete phylogeny, diversity and disparity. Royal Society Open Science 2:140434 [M. Uhen/M. Uhen]
12148 M. Oishi and Y. Hasegawa. 1995. A list of fossil cetaceans in Japan. The Island Arc 3:493-505 [M. Uhen/M. Uhen/M. Uhen]
38169 T. Saito, J. A. Barron, and MSakamoto. 1988. An Early Late Oligocene Age indicated by Diatoms for a Primitive Desmostylian Mammal Behemotops from Eastern Hokkaido, Japan. Proceedings of the Japan Academy Ser. B: Physical and Biological Sciences 64(9):269-273 [M. Uhen/M. Uhen]
95707 H. Sawamura. 2008. The origin of baleen whale－Comparative morphology of the toothed Mysticetes and the minke whale fetuses. Journal of Fossil Research 40(2):120-130 [M. Uhen/M. Uhen]
55066 C.-H. Tsai and T. Ando. 2015. Niche Partitioning in Oligocene Toothed Mysticetes (Mysticeti: Aetiocetidae). Journal of Mammalian Evolution [M. Uhen/M. Uhen]