Khok Kruat Formation

The Khok Kruat Formation (Thai: หมวดหินโคกกรวด) is a rock formation found in northeastern Thailand. It is the uppermost formation of the Khorat Group.^[1] It is dated to the Aptian stage of the Early Cretaceous period, and is notable for its fossils of dinosaurs. It is equivalent to the Gres superieurs Formation of Laos.^[2] The group is a fluvial formation consisting primarily of red siltstones and sandstones.^[1]

Khok Kruat Formation
Stratigraphic range: Aptian ~120–113 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Khorat Group
Underlies	Maha Sarakham Formation
Overlies	Phu Phan Formation
Lithology
Primary	Sandstone, siltstone
Other	Conglomerate, shale
Location
Coordinates	15.9°N 102.0°E / 15.9; 102.0
Approximate paleocoordinates	16.3°N 105.3°E / 16.3; 105.3
Region	Indochina
Country	Thailand
Extent	Khorat Plateau
Type section
Named by	Ward & Bunnag
Year defined	1964
Khok Kruat Formation (Thailand)

Vertebrate paleofauna

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

The Khok Kruat Formation has yielded remains of sharks, fishes, turtles, crocodilians and pterosaurs. Phuwiangosaurus-like teeth, Siamosaurus teeth, and fragmentary postcranial remains of spinosaurids have also been recovered from it.^[3] Fukuiraptor-like teeth have also been recovered from the formation.^[4]

Reptiles

Dinosaurs

Dinosaurs reported from the Khok Kruat Formation
Genus	Species	Location	Material	Notes	Images
cf. Asianopodus	cf. A. isp.	"Huai Dam Chum site, Ban Lao Nat, Tha Uthen District, Nakhon Phanom Province".[5]	"At least 79 trackways composed of 341 consecutive tracks in total".[5]	Theropod tracks.
Ichnogen. et. sp. indet.		"Huai Dam Chum site, Ban Lao Nat, Tha Uthen District, Nakhon Phanom Province".[5]	"Two trackways: T23 composed of 6 consecutive tracks and T35 composed of 3 discontinuous tracks".[5]	Flattened possible theropod tracks.
Ornithomimosauria[6]	Indeterminate	Ban Krok Duean Ha	"NRRU-F01020052, distal part of the right metatarsal III"	An ornithomimosaurian
Psittacosaurus	P. sattayaraki[7]	Ban Dong Bang Noi, Chaiyaphum Province	"Well preserved left dentary and an incomplete maxilla."[3]	A ceratopsian
Ratchasimasaurus	R. suranareae	Nakhon Ratchasima province.[8]		An iguanodontian ornithopod
Siamodon	S. nimngami[9]	Ban Saphan Hin	PRC-4, a well-preserved left maxilla, PRC-5, an isolated maxillary tooth and PRC-6, a braincase.[9]	An iguanodontian ornithopod
Sirindhorna	S. khoratensis	Muaeng Nakhon Ratchasima District, Nakhon Ratchasima Province.[10]		An iguanodontian ornithopod
Siamosaurus	S. sp.[11]		Teeth	A spinosaurid
Siamraptor	S. suwati	Muaeng Nakhon Ratchasima District, Nakhon Ratchasima Province.[12]	"A composite cranial and postcranial skeleton comprising premaxilla, maxilla, jugal, surangular, prearticular, articular, vertebrae, manual ungual, ischium, tibia, and pedal phalanx".[12]	A carcharodontosaur

Pseudosuchians

Pseudosuchians reported from the Khok Kruat Formation
Genus	Species	Location	Material	Notes	Images
Atoposauridae indet.	Indeterminate	Lam Pao Reservoir, Ban Noi, Sahatsakhan district, Kalasin province.[13]	An isolated lanceolate tooth (PRCMR 282).[13]	May be attributable to Theriosuchus.[13]
Khoratosuchus	K. jintasakuli	Ban Saphan Hin, Nakhon Ratchasima province.[14]	A partial skull (NNRU-A 1803).[14]	An advanced neosuchian.

Turtles

Turtles reported from the Khok Kruat Formation
Genus	Species	Location	Material	Notes	Images
Kizylkumemys	K. khoratensis	Ban Saphan Hin and Ban Khok Kruat localities, Nakhon Ratchasima province.[15]	Shell material.[15]	A carettochelyid.
Shachemys	S. sp.	Ban Saphan Hin, Nakhon Ratchasima province.[15]	Shell material.[15]	An adocid, remains too fragmentary for specific assignment.

Fish

Bony fish

Bony fish reported from the Khok Kruat Formation
Genus	Species	Location	Material	Notes	Images
Khoratamia	K. phattharajani	Ban Krok Duean Ha, Nakhon Ratchasima province.[16]	Holotype (NRRU-F01020023), paratype (NRRU-F01020024) and a patch of scales (NRRU-F01020025).[16]	An amiid.
Lanxangichthys	L. sp.	Khok Pha Suam, Ubon Ratchathani province.[17]		A lepisosteiform.

Cartilaginous fish

Cartilaginous fish reported from the Khok Kruat Formation
Genus	Species	Location	Material	Notes	Images
Acrorhizodus	A. khoratensis	Khok Pha Suam locality, Ubon Ratchathani province.[18]	5 teeth, most of them incomplete.[18]	A hybodontiform.
Heteroptychodus	H. aff. steinmanni	Khok Pha Suam locality, Ubon Ratchathani province.[18]	20 teeth, most incomplete.[18]	A ptychodontid.
Hybodus?	H.? sp.	Khok Pha Suam locality, Ubon Ratchathani province.[18]	22 incomplete teeth.[18]	Possibly represents a new genus, but the available material is too fragmentary to warrant erecting a new taxon.[18]
Thaiodus	T. ruchae	Khok Pha Suam locality, Ubon Ratchathani province.[18]	One incomplete tooth.[18]	A hybodontid.

See also

• List of dinosaur-bearing rock formations