Ohyamashimo Formation
Geologic formation in Japan
Ohyamashimo Formation | |
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Stratigraphic range: Albian ~112.1–106.4 Ma PreꞒ Ꞓ O S D C P T J K Pg N | |
Type | Geological formation |
Unit of | Sasayama Group |
Underlies | Sawada Formation |
Overlies | Basement (Unconformity) |
Thickness | 1300 metres |
Lithology | |
Primary | Conglomerate, Sandstone, Mudstone |
Other | Tuff |
Location | |
Coordinates | Ohyamashimo Formation (Japan) |
The Ohyamashimo Formation(大山下層) is an Early Cretaceous (Albian) geologic formation in Japan. It has been dated to the early-mid Albian, between 112.1 ± 0.4 Ma and 106.4 ± 0.4 Ma. Dinosaur remains have been discovered from this formation, including the sauropod Tambatitanis, the theropod Hypnovenator and the ceratopsian Sasayamagnomus. Other representative fossils from the formation include the monstersaurian lizard Morohasaurus and eutherian mammal Sasayamamylos. The depositional environment represents a fluvial system with a subhumid to semi-arid climate.
Fossil Records
Arthropods
Arthropods reported from the Ohyamashimo Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Mongolocypris | M. sp. | An ostracod. | ||||
Conchostraca | indeterminate |
Molluscs
Molluscs reported from the Ohyamashimo Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Viviparus | V. cf. keishoensis | A gastropod. | ||||
Sphaerium | S. coreanicum | A bivalve. |
Amphibians
Amphibians reported from the Ohyamashimo Formation[2] | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Hyogobatrachus | H. wadai | A nearly complete skeleton. | Forms a sister group with the Lalagobatrachia. | |||
Tambabatrachus | T. kawazu | An articulated skeleton lacking the anterior part of the skull, most of the pectoral girdle, manus, and feet. |
Mammals
Mammals reported from the Ohyamashimo Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Sasayamamylos[3] | S. kawaii | Three dentaries. | An asioryctitherian mammal. |
Lizards
Lizards reported from the Ohyamashimo Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Morohasaurus[4] | M. kamitakiensis | A nearly complete left dentary. | A monstersaurian lizard. | |||
Pachygenys[5] | P. adachii | A single, partially broken right mandible |
Dinosaurs
Dinosaurs reported from the Ohyamashimo Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Tambatitanis[6] | T. amicitiae | A single partial skeleton. | A titanosauriform sauropod. | |||
Tyrannosauroidea | Indeterminate | Dental remains. | ||||
Therizinosauria | Indeterminate | Dental remains. | ||||
Dromaeosauridae | Indeterminate | Dental remains. | ||||
Hypnovenator[7] | H. matsubaraetoheorum | A single partial skeleton. | A troodontid theropod. | |||
Ankylosauria | Indeterminate | Dental remains. | ||||
Iguanodontia | Indeterminate | Dental remains. | ||||
Sasayamagnomus[8] | S. saegusai | Skull elements and partial postcranial remains. | A neoceratopsian. |
Oofossils
Eggs reported from the Ohyamashimo Formation[9][10] | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Himeoolithus | H. murakamii | |||||
Subtiliolithus | S. hyogoensis | |||||
Prismatoolithus | P. sp. | |||||
Nipponoolithus | N. ramosus | |||||
Elongatoolithus | E. sp. | |||||
Spheroolithus | S. sp. |
References
- ^ Hayashi, Keiichi; Fujita, Saki; Koarai, Kazuto; Matsukawa, Masaki (2017-09-15). "Stratigraphy and paleoenvironment of the Cretaceous Sasayama Group in the Sasayama area, Hyogo Prefecture, western Japan". The Journal of the Geological Society of Japan. 123 (9): 747–764. doi:10.5575/geosoc.2017.0016. ISSN 0016-7630.
- ^ Ikeda, Tadahiro; Ota, Hidetoshi; Matsui, Masafumi (June 2016). "New fossil anurans from the Lower Cretaceous Sasayama Group of Hyogo Prefecture, Western Honshu, Japan". Cretaceous Research. 61: 108–123. doi:10.1016/j.cretres.2015.12.024.
- ^ Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki (22 May 2013). "A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan". Proceedings of the Royal Society B: Biological Sciences. 280 (1759): 20130142. doi:10.1098/rspb.2013.0142. PMC 3619506.
- ^ Ikeda, Tadahiro; Ota, Hidetoshi; Tanaka, Tomonori; Ikuno, Kenji; Kubota, Katsuhiro; Tanaka, Kohei; Saegusa, Haruo (February 2022). "A fossil Monstersauria (Squamata: Anguimorpha) from the Lower Cretaceous Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan". Cretaceous Research. 130: 105063. doi:10.1016/j.cretres.2021.105063.
- ^ Ikeda, Tadahiro; Ota, Hidetoshi; Saegusa, Haruo (2 January 2015). "A new fossil lizard from the Lower Cretaceous Sasayama Group of Hyogo Prefecture, western Honshu, Japan". Journal of Vertebrate Paleontology. 35 (1): e885032. doi:10.1080/02724634.2014.885032.
- ^ Saegusa, Haruo; Ikeda, Tadahiro (12 August 2014). "A new titanosauriform sauropod (Dinosauria: Saurischia) from the Lower Cretaceous of Hyogo, Japan". Zootaxa. 3848 (1). doi:10.11646/zootaxa.3848.1.1.
- ^ Kubota, Katsuhiro; Kobayashi, Yoshitsugu; Ikeda, Tadahiro (25 July 2024). "Early Cretaceous troodontine troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan reveals the early evolution of Troodontinae". Scientific Reports. 14 (1). doi:10.1038/s41598-024-66815-2. PMC 11272788.
- ^ Tanaka, Tomonori; Chiba, Kentaro; Ikeda, Tadahiro; Ryan, Michael J. (September 2024). "A new neoceratopsian (Ornithischia, Ceratopsia) from the Lower Cretaceous Ohyamashimo Formation (Albian), southwestern Japan". Papers in Palaeontology. 10 (5). doi:10.1002/spp2.1587.
- ^ Tanaka, Kohei; Zelenitsky, Darla K.; Saegusa, Haruo; Ikeda, Tadahiro; DeBuhr, Christopher L.; Therrien, François (January 2016). "Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods". Cretaceous Research. 57: 350–363. doi:10.1016/j.cretres.2015.06.002.
- ^ Tanaka, Kohei; Zelenitsky, Darla K.; Therrien, François; Ikeda, Tadahiro; Kubota, Katsuhiro; Saegusa, Haruo; Tanaka, Tomonori; Ikuno, Kenji (October 2020). "Exceptionally small theropod eggs from the Lower Cretaceous Ohyamashimo Formation of Tamba, Hyogo Prefecture, Japan". Cretaceous Research. 114: 104519. doi:10.1016/j.cretres.2020.104519.