Kuwajima Formation

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
Stratigraphic range: Barremian PreꞒ Ꞓ O S D C P T J K Pg N ↓
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			Monjurosuchus
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"		Kaganaias
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
Unio	U. ogamigoensis				Unionid
Sphaerium	S. sp.				Sphaeriid
Viviparus	V. onogoensis				Viviparid
Micromelania	M.? katoensis				Sphaeriid
Physidae	Indeterminate, two species
Pupilloidea	Indeterminate

See also

• Earth sciences portal
• Paleontology portal
• Dinosaurs portal

• List of dinosaur-bearing rock formations