Bissekty Formation

The lithology of the sediment largely consists of cross bedded sandstones with interbeds of massive sandstone, well cemented intraformational conglomerate, siltstones and mudstones. Most of the fossils are found as clasts within the conglomerates.^[2]

The Bissekty Formation is characterised by a mix of marine, brackish, freshwater, and terrestrial animal fossils. This stands in contrast the strictly marine fossils found in the underlying Dzheirantui Formation, and indicates that the Bissekty was formed during the regression of a saltwater sea. The coastline expanded inland again in the upper portion of the Bissekty, represented by a proportional increase of fully aquatic species, which were almost completely absent from the middle period of the formation. Semi-aquatic species remained abundant during this middle period, and the geology of the formations indicates that a braided river system took the place of the coastline. Eventually the area was again completely underwater, during the time period represented by the later Aitym Formation, which preserves coastal marine sediments.^[2]

Vertebrates

The Bissekty Formation is notable for preserving the most abundant Turonian land animal fossils in Eurasia, and the most diverse fauna of Late Cretaceous eutherians (placental mammals and relatives) in the world.^[2]

Listings and accompanying information are based on a survey of the Bissekty Formation published by Cory Redman and Lindsey Leighton in 2009 unless otherwise noted.^[2] Aquatic and semi-aquatic species are restricted to freshwater unless otherwise noted.

Amphibians

An indeterminate species of salamander-like albanerpetontid amphibian. An indeterminate gobiatid species.

More information Amphibians of the Bissekty Formation, Genus ...

Amphibians of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Aralobatrachus	A. robustus				A frog
Eoscapherpeton	E. asiaticum				A scapherpetontid salamander
Gobiates	G. sosedkoi				A gobiatid frog
	Gobiates spp.				Additional indeterminate species of Gobiates
Itemirella	I. cretacea				A possible discoglossid frog
Kizylkuma	K. antiqua				A possible discoglossid marine frog
Mynbulakia	M. surgai				A batrachosauroidid salamander
Nesovtriton	N. mynbulakensis				A cryptobranchoid salamander

Close

Cartilaginous fish

More information Cartilaginous fishes of the Bissekty Formation, Genus ...

Cartilaginous fishes of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Cretodus	C. crassidens				A marine Pseudoscapanorhynchid Lamniform shark
Heterodontus	Indeterminate				A marine bullhead shark
Hispidaspis	Indeterminate				A sand shark tolerant of brackish water
Hybodus	Indeterminate				A hybodontid tolerant of brackish water
Ischyrhiza	I. serra				A sclerorhynchid tolerant of brackish water
Myledaphus	M. tritus				A rhinobatoid tolerant of brackish water
Polyacrodus	Indeterminate				A polyacrodontid tolerant of brackish water
Scapanorhynchus	S. rhaphiodon				A goblin shark tolerant of brackish water

Close

Crocodylomorphs

More information Crocodylomorphs of the Bissekty Formation, Genus ...

Crocodylomorphs of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Kansajsuchus	K. borealis				A possible goniopholidid mesoeucrocodylian
Tadzhikosuchus	T. macrodentis				A possible alligatoroid eusuchian
Zholsuchus	Z. procevus				A possible mesoeucrocodylian
Zhyrasuchus	Z. angustifrons				A possible eusuchian

Close

Lizards

An indeterminate gekkonid. An indeterminate priscagamid. An indeterminate scincid.

More information Lizards of the Bissekty Formation, Genus ...

Lizards of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Buckantaus	B. crassidens				A macrocephalosaurid
Ekshmer	E. bissektensis				A priscagamid

Close

Mammals and other therapsids

More information Mammaliaformes of the Bissekty Formation, Genus ...

Mammaliaformes of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Aspanlestes	A. aptap				A zhelestid
Bulaklestes	B. kezbe				An asioryctitherian
Daulestes	D. inobservabilis				An asioryctitherian
	D. kulbeckensis				An asioryctitherian
Eoungulatum	E. kudukensis				A zhelestid
Kulbeckia	K. kulbecke				A zalambdalestid
Paranyctoides	P. quadrans				An eutherian
Parazhelestes	P. mynbulakensis				A zhelestid
	P. robustus				A zhelestid
Shalbaatar	S. bakht				A symmetrodont
Sulestes	S. karakshi				A deltatheroid
Uchkudukodon	U. nessovi				An asioryctitherian
Uzbekbaatar	U. kizylkumensis				A cimolodont
Zhelestes	Z. temirkazyk				A zhelestid

Close

Plesiosaurs

More information Plesiosaurs of the Bissekty Formation, Genus ...

Plesiosaurs of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Plesiosauria	Indeterminate				Marine, possibly tolerant of brackish water

Close

Pterosaurs

More information Pterosaurs of the Bissekty Formation, Genus ...

Pterosaurs of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Azhdarcho	A. lancicollis	Dzhara-Kuduk	Taykarshinskaya unit		An azhdarchid

Close

Ray-finned fish

Based on Brinkman et al (2025):^[3]

More information Ray-finned fish of the Bissekty Formation, Genus ...

Ray-finned fish of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Acanthomorpha indet.					An acanthomorph of uncertain affinities.
Aidachar	A. paludalis				An ichthyodectiform tolerant of brackish water
"Amia"	"A." limosa				A bowfin tolerant of brackish water. Potentially a nomen dubium[4], but some studies consider it valid.[3]
?Anguilliformes indet.					A potential eel of uncertain affinities.
Arotus	A. hieroglyphus				A holostean, potentially a semionotiform, known from isolated scales.[5]
Atractosteus	A. turanensis				A gar tolerant of brackish water
Belonostomus	B. aciculiferus				An aspidorhynchid
Characiformes indet.					A characiform of uncertain affinities.
Clupeiformes indet.					A clupeiform of uncertain affinities.
cf. Coriops					An osteoglossomorph.
Diplomystus	D. sp.				An ellimmichthyiform.
Gonorynchiformes indet.					A gonorynchiform of uncertain affinities.
Notogoneus	N. sp.				A beaked sandfish.
cf. Paratarpon					An elopiform.
Polyodontidae indet.					A paddlefish of uncertain affinities.

Close

Dinosaurs

Sauropods

More information Sauropods of the Bissekty Formation, Genus ...

Sauropods of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Material	Description	Images
Dzharatitanis	D. kingi			An anterior caudal vertebra.	Originally described as a rebbachisaurid, a later study has suggested it was lognkosaurian titanosaur[6]
Titanosauria	Indeterminate			CCMGE 628/12457, a braincase

Close

Ornithischians

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.

More information Ornithischians reported from the Bissekty Formation, Genus ...

Ornithischians reported from the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Material	Description	Images
Amtosaurus	A. archibaldi[7]				Reclassified as Bissektipelta[8]
Bactrosaurus	B. kyslkumensis			"Fragmentary dentary [=maxilla], vertebrae, tibia."[9]	Nomen dubium
Bissektipelta	B. archibaldi[8]			"Partial skull."[10]	An ankylosaur
Cionodon	C. kyslkumensis[7]				Reclassified as Bactrosaurus kyslkumensis[8]
Gilmoreosaurus	G. arkhangelskyi				Nomen dubium
Levnesovia	L. transoxiana			"Braincases"	A hadrosauroid
Turanoceratops[7]	T. tardabilis[7]				A ceratopsian[11]

Close

Theropods

An indeterminate tyrannosauroid species, known from isolated teeth.^[12]

Carcharodontosauridae

More information Carcharodontosaurs of the Bissekty Formation, Genus ...

Carcharodontosaurs of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Material	Description	Images
Carcharodontosauridae	Indeterminate			A partial posterior dorsal vertebra[13]
Ulughbegsaurus	U. uzbekistanensis			A left maxilla, the ramus end of a left maxilla, and the posterior end of a right maxilla.	A carcharodontosaurid theropod

Close

Enantiornithines

More information Enantiornithines of the Bissekty Formation, Genus ...

Enantiornithines of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Material	Description	Images
Abavornis	A. bonaparti			Known from a partial coracoid[14]	A possible enantiornithine.[14] A possible second species of Abavornis in the Bissekty Formation is known from a partial coracoid.[14]
Catenoleimus	C. anachoretus				A possible enantiornithine
Explorornis	E. nessovi				An enantiornithine. Possible third and fourth species of Explorornis in the Bissekty Formation are known from partial coracoids.[14]
	E. walkeri			"Coracoid"[15]
Ichthyornis	I. minusculus			"Dorsal vertebra"[16]	An enantiornithine originally but incorrectly identified as a species of Ichthyornis.[17]
Incolornis	I. martini			Known from a partial coracoid[14]	A possible enantiornithine[14]
	I. silvae			Known from a partial coracoid[14]	A possible enantiornithine[14]
Kizylkumavis[7]	K. cretacea[7]			"Distal humerus"[15]	An enantiornithine
Kuszholia	K. mengi			"[Two] synsacra"[18]	An enantiornithine
Lenesornis[7]	L. maltshevskyi[7]			"Synsacrum"[15]	A possible enantiornithine
cf. Nanantius					An enantiornithine, similar to Nanantius eos
Sazavis[7]	S. prisca[7]			"Distal tibiotarsus"[19]	An enantiornithine
Zhyraornis[7]	Z. kashkarovi[7]			"Synsacrum"[19]
	Z. logunovi[7]			"Synsacrum"[19]

Close

Other theropods

More information Non-enantiornithine theropod dinosaurs of the Bissekty Formation, Genus ...

Non-enantiornithine theropod dinosaurs of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Material	Description	Images
Caenagnathasia	C. martinsoni			"[Two] partial mandibles"[20]	An elmisaurine caenagnathid
Dzharacursor	D. bissektensis			Right femur of a juvenile (holotype) with partial cranial and postcranial material[21]	An ornithomimosaur originally assigned to Archaeornithomimus
Dzharaonyx	D. eski				An alvarezsaur
Euronychodon	E. asiaticus			Isolated teeth[22][23][24]	A possible troodontid
Itemirus	I. medullaris			A single small, damaged fossil braincase	A dromaeosaurine
Platanavis[7]	P. nana[7]			"Sacrum"[16]
Therizinosauroidea spp.[25]	Indeterminate			Partial crania also preserving some teeth and some postcranial elements including pedal bones (from multiple individuals)	At least two different therizinosauroids
Timurlengia[26]	T. euotica			Two braincases, dentary, and miscellaneous postcranial elements (from multiple individuals)	A non-tyrannosaurid tyrannosauroid
Urbacodon	Unnamed species			Isolated teeth[27]	A troodontid
Zhyraornis	Z. kashkarovi				A possible ornithurine
Dromaeosauridae indet.	Indeterminate			Pedal phalanx	A large indeterminate dromaeosaurid[28]

Close

Turtles

An indeterminate trionychid (soft-shell) turtle species that was tolerant of brackish water.

More information Turtles of the Bissekty Formation, Genus ...

Turtles of the Bissekty Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
"Adocus"	"Adocus" aksary				An adocid tolerant of brackish water
Anatolemys	Indeterminate				A "macrobaenid" tolerant of brackish water
Khunnuchelys	K. kizylkumensis				A trionychid tolerant of brackish water
Lindholmemys	L. elegans				A "lindholmemydid" tolerant of brackish water
Shachemys	S. ancestralis				An adocid tolerant of brackish water

Close