Kuwajima Formation
Early Cretaceous geologic formation in Japan
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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]
Unit ofTetori Group
Sub-unitsLower Member, Upper Member
UnderliesAkaiwa Formation
OverliesGomijima Formation
| Kuwajima Formation | |
|---|---|
| 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]
Vertebrate Paleobiota
After Matsuoka et al. (2002)[6]
Fish
| Fish reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| 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 | ||||
| Lepidotes | L. sp. | |||||
| Pachycormidae | Indeterminate | Jaw | ||||
Amphibians
| Amphibians reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Shirerpeton[7] | 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"[8] | Partial skeleton belongs to a basal frog that lies outside of Neobatrachia.[8] | |||
Choristoderes
| Choristoderes reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Monjurosuchus | Indeterminate | Kaseki-kabe | Facies III |
 | ||
| Neochoristodera[9] | Indeterminate | Facies I | The first report of a neochoristodere from Japan | |||
| Choristodera | Indeterminate | Kaseki-kabe | Facies III | |||
Squamates
| Squamates reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| 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[10] | 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
| 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[11] | Indeterminate | Right dentary, left maxilla, isolated teeth | Distinct from Albalophosaurus | |||
| Sauropoda ("Oharasisaurus") | Indeterminate | Kaseki-kabe | Facies III | Tooth[12] | ||
| Styracosterna[11] | Indeterminate | Maxillary and dental teeth | ||||
Other reptiles
| Choristoderes reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Trionychidae | Indeterminate | Kaseki-kabe | ||||
| Testudinoidea | Indeterminate | Kaseki-kabe | ||||
| Sinemydidae | Indeterminate | Kaseki-kabe | ||||
| Ornithocheiridae | Indeterminate | Kaseki-kabe | ||||
| Gnathosaurinae | Indeterminate | Kaseki-kabe | ||||
| Dsungaripteroidea? | Indeterminate | Kaseki-kabe | ||||
Mammaliamorphs
| Mammaliamorphs reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Hakusanobaatar[4] | H. matsuoi | Kaseki-kabe | Facies III | Dentary fragments and teeth | Eobaatarid | |
| Hakusanodon[13] | 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 | |||
Invertebrate Paleobiota
| Invertebrates reported from the Kuwajima Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Nipponoridium | B. matsuoi | Kaseki-Kabe | Mimarachnid hemipteran | |||
| Nipponohagla | N. kaga | Prophalangopsid | ||||
| Kagapsychops | K. araneus | Psychopsid | ||||
| Coleoptera | Indeterminate | |||||
| Margaritifera | M. ogamigoensis | Previously classified as Unio ogamigoensis.[14] | ||||
| Nakamuranaia | N. kagaensis | Trigonioidoid bivalve; previously considered to be ?Unio ogamigoensis[14]. | ||||
| Sphaerium | S. sp. | Sphaeriid | ||||
| Viviparus | V. onogoensis | Viviparid | ||||
| Micromelania | M.? katoensis | |||||
| Physidae | Indeterminate, two species | |||||
| Pupilloidea | Indeterminate | |||||
