The Kuwajima Formation is an Early Cretaceous geologic formation in Japan. Its precise age is uncertain due to a lack of identifying fossils, and it was previously considered likely Valanginian to Hauterivian in age.[1] However, it is now considered to probably be Barremian in age.[2] Dinosaurs and other vertebrates has been recovered from the Kaseki-kabe "Fossil-bluff" locality in the uppermost part of the formation.[3]
Kuwajima Formation | |
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Stratigraphic range: | |
Unit of | Tetori Group |
Sub-units | Lower Member, Upper Member |
Underlies | Akaiwa Formation |
Overlies | Gomijima Formation |
Lithology | |
Primary | Sandstone, Mudstone |
Location | |
Country | Japan |
The multituberculate mammals Hakusanobaatar matsuoi and Tedoribaatar reini are known from the Kuwajima Formation.[4] A member of Tritylodontidae, Montirictus kuwajimaensis, has also been recovered from the unit.[5]
Fish reported from the Kuwajima Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Sinamia | S. kukurihime | Mostly complete skeleton | An amiiform fish related to bowfins | |||
Tetoriichthys | T. kuwajimaensis | The oldest record of Osteoglossiform |
Amphibians reported from the Kuwajima Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Shirerpeton[6] | S. isajii | Kaseki-kabe | Facies III | Partial disarticulated skull | Albanerpetontid | |
Anura | Indeterminate | Isolated longbone, as well as a partial skeleton "composed of a few skull elements and several postcranial bones, including the femur, ilium, and vertebrae"[7] | Partial skeleton belongs to a basal frog that lies outside of Neobatrachia.[7] |
Choristoderes reported from the Kuwajima Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Monjurosuchus | Indeterminate | Kaseki-kabe | Facies III | |||
Neochoristodera[8] | Indeterminate | Facies I | The first report of a neochoristodere from Japan | |||
Choristodera | Indeterminate | Kaseki-kabe | Facies III |
Squamates reported from the Kuwajima Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Asagaolacerta | A. tricuspidens | Kaseki-kabe | Facies III | "An association of skull, jaws and postcranial bones of a small lizard with facetted tricuspid teeth, possibly a right maxilla" | ||
Hakuseps | H. imberis | Kaseki-kabe | Facies III | An almost complete left dentary | ||
Kaganaias | K. hakusanensis | Kaseki-kabe | Facies III | "Part and counterpart of articulated partial skeleton comprising parts of the dors. vert. series and parts of the tail, pelvis, and hind limbs" | ||
Kuroyuriella | K. mikikoi | Kaseki-kabe | Facies III | "A disarticulated skull on four originally conjoined blocks, an association on two small blocks" | ||
Kuwajimalla[9] | K. kagaensis | Kaseki-kabe | Facies III | |||
Sakurasaurus | Indeterminate | Kaseki-kabe | Facies III | "Small block with disarticulated association of skull bones, vertebrae, ribs, pelvis and hindlimb bones" | ||
Paramacellodidae | Indeterminate | Kaseki-kabe | Facies III | |||
Squamata | Indeterminate | Kaseki-kabe | Facies III | Five distinct taxa |
Dinosaurs reported from the Kuwajima Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Albalophosaurus[3] | A. yamaguchiorum | Kaseki-kabe | Facies III | Partial skull and lower jaws | ||
Dromaeosauridae | Indeterminate | Kaseki-kabe | Facies III | |||
Enantiornithes | Indeterminate | Kaseki-kabe | Facies III | |||
Ornithischia[10] | Indeterminate | Right dentary, left maxilla, isolated teeth | Distinct from Albalophosaurus | |||
Sauropoda ("Oharasisaurus") | Indeterminate | Kaseki-kabe | Facies III | Tooth[11] | ||
Styracosterna[10] | Indeterminate | Maxillary and dental teeth |
Mammaliamorphs reported from the Kuwajima Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Hakusanobaatar[4] | H. matsuoi | Kaseki-kabe | Facies III | Dentary fragments and teeth | Eobaatarid | |
Hakusanodon[12] | H. archaeus | Kaseki-kabe | Facies III | Eutriconodont | ||
Montirictus[5] | M. kuwajimaensis | Kaseki-kabe | Facies III | Tritylodontid | ||
Tedoribaatar[4] | T. reini | Kaseki-kabe | Facies III | "Fragment of right lower jaw with p4" | Eobaatarid | |
Multituberculata | Indeterminate | Kaseki-kabe | Facies III |
Invertebrates reported from the Kuwajima Formation | ||||||
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Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Nipponoridium | B. matsuoi | Kaseki-Kabe | Mimarachnid hemipteran | |||
Nipponohagla | N. kaga | Prophalangopsid | ||||
Kagapsychops | K. araneus | Psychopsid |