Earth:Bissekty Formation

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Bissekty Formation
Stratigraphic range: Mid-Late Turonian
~92–90 Ma
↓
TypeGeological formation
UnderliesAitym Formation
OverliesDzheirantui Formation
Thicknessup to 80 m (260 ft)
Lithology
PrimarySandstone
OtherConglomerate, mudstone, siltstone
Location
Coordinates [ ⚑ ] : 42°06′N 62°42′E / 42.1°N 62.7°E / 42.1; 62.7
Paleocoordinates [ ⚑ ] 36°48′N 57°00′E / 36.8°N 57.0°E / 36.8; 57.0
RegionNavoiy & Xorazm Regions
CountryUzbekistan
ExtentKyzylkum Desert
Bissekty Formation is located in Uzbekistan
Bissekty Formation
Bissekty Formation
Bissekty Formation (Uzbekistan)

The Bissekty Formation (sometimes referred to as Bissekt) is a geologic formation and Lagerstätte which crops out in the Kyzyl Kum desert of Uzbekistan, and dates to the Late Cretaceous Period. Laid down in the mid to late Turonian, it is dated to about 92 to 90 Ma (million years ago).[1]

Description

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]

Fossil content

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.

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

Cartilaginous fish

Cartilaginous fishes of the Bissekty Formation
Genus Species Location Stratigraphic position Abundance Notes Images
Cretodus C. crassidens A marine Pseudoscapanorhynchid Lamniform shark
Cretodus_crassidens
Heterodontus Indeterminate A marine bullhead shark
Hornhai_(Heterodontus_francisci)
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 thumb
Myledaphus M. tritus A rhinobatoid tolerant of brackish water
Myledaphus_skeleton
Polyacrodus Indeterminate A polyacrodontid tolerant of brackish water
Scapanorhynchus S. rhaphiodon A goblin shark tolerant of brackish water

Crocodylomorphs

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

Lizards

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

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

Mammals and other therapsids

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

Plesiosaurs

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

Pterosaurs

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

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

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 frameless
"Amia" "A." limosa A bowfin tolerant of brackish water. Potentially a nomen dubium[4], but some studies consider it valid.[3] frameless
?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 frameless
Belonostomus B. aciculiferus An aspidorhynchid frameless
Characiformes indet. A characiform of uncertain affinities.
Clupeiformes indet. A clupeiform of uncertain affinities.
cf. Coriops An osteoglossomorph. frameless
Diplomystus D. sp. An ellimmichthyiform. frameless
Gonorynchiformes indet. A gonorynchiform of uncertain affinities.
Notogoneus N. sp. A beaked sandfish. frameless
cf. Paratarpon An elopiform. frameless
Polyodontidae indet. A paddlefish of uncertain affinities.

Dinosaurs

Sauropods
Sauropod dinosaurs 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
Ornithischians

Template:Paleobiota-key-compact

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]
Theropods

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

Carcharodontosauridae
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 probable carcharodontosaurid theropod
Enantiornithines
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]
Other theropods
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

Turtles

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

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

Invertebrates

An indeterminate species of marine coral.

Arthropods

Arthropods of the Bissekty Formation
Genus Species Location Stratigraphic position Abundance Notes
Linuparus L. dzheirantuiensis Marine A spiny lobster

Molluscs

An indeterminate species of marine placenticeratid ammonite. An indeterminate species of marine teredinid shipworm. An indeterminate marine trigoniid bivalve. An indeterminate marine veneroid bivalve.

Molluscs of the Bissekty Formation
Genus Species Location Stratigraphic position Abundance Notes
Crassatelites Indeterminate A marine crassatellid bivalve
Mytiloides M. labiatus A marine inoceramid bivalve
Plagiostoma Indeterminate A marine limoid bivalve
Quadratotrigonia Indeterminate A marine trigoniid bivalve
Xylophaga Indeterminate An indeterminate species of marine shipworm

References

  1. ↑ Averianov, Alexander; Sues, Hans-Dieter (April 2012). "Skeletal remains of Tyrannosauroidea (Dinosauria: Theropoda) from the Bissekty Formation (Upper Cretaceous: Turonian) of Uzbekistan". Cretaceous Research 34: 284–297. doi:10.1016/j.cretres.2011.11.009. ISSN 0195-6671. Bibcode: 2012CrRes..34..284A. 
  2. ↑ 2.0 2.1 2.2 2.3 Redman & Leighton, 2009
  3. ↑ 3.0 3.1 Brinkman, Donald B.; Kundrát, Martin; Ward, David J.; Murray, Alison M.; Aimbetov, Izzet K.; Van Loon, Lisa L.; Banerjee, Neil R. (2026-02-01). "Fish Faunas from the Bissekty Formation (Turonian), Uzbekistan: Insights into biogeographic connectivity and climate-driven Faunal Turnover". Cretaceous Research 179: 106252. doi:10.1016/j.cretres.2025.106252. ISSN 0195-6671. https://www.sciencedirect.com/science/article/pii/S0195667125001752. 
  4. ↑ Grande, G; Bemis, E (2014). A comprehensive phylogenetic study of amiid fishes (Amiidae) based on comparative skeletal anatomy. An empirical search for interconnected patterns of natural history. (project). doi:10.7934/p482. 
  5. ↑ Gardner, James D.; Brinkman, Donald B.; Murray, Alison M. (2025-06-01). "Reidentification of the holotype of ‘Ceratodus’ hieroglyphus Cope from the Upper Cretaceous (Campanian) of Montana, USA, as the scale of a holostean fish" (in en). Palaeobiodiversity and Palaeoenvironments 105 (2): 545–572. doi:10.1007/s12549-025-00663-4. ISSN 1867-1608. https://doi.org/10.1007/s12549-025-00663-4. 
  6. ↑ Lerzo, Lucas Nicolás; Carballido, José Luis; Gallina, Pablo Ariel (30 April 2021). "¿Saurópodos Rebbaquisáuridos en Asia? Una Re-Evaluación de la Posición Filogenética de Dharatitanis Kingi del Cretácico Tardío de Uzbekistán" (in en). Publicación Electrónica de la Asociación Paleontológica Argentina 21 (1): 18–27. doi:10.5710/PEAPA.24.03.2021.389. ISSN 2469-0228. https://www.peapaleontologica.org.ar/index.php/peapa/article/view/Pdf. 
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 7.14 "Dinosaur distribution (Bissekty Formation)." Weishampel, et al. (2004). Pg. 594.
  8. ↑ 8.0 8.1 8.2 Averianov, 2002
  9. ↑ "Table 20.1," in Weishampel, et al. (2004). Page 442.
  10. ↑ "Table 17.1," in Weishampel, et al. (2004). Page 367.
  11. ↑ Sues & Averianov, 2009
  12. ↑ Archibald, James David; Sues, Hans-Dieter; Averianov, Alexander; King, Chris; Ward, David John; Tsaruk, Oleg; Danilov, Igor; Rezvyi, Anton et al. (1998). "Precis of the Cretaceous paleontology, biostratigtaphy and sedimentology at Dzharakuduk (Turonian?-Santonian), Kyzylkum Desert, Uzbekistan". Bulletin of the New Mexico Museum of Natural History and Science 14: 21–27. 
  13. ↑ Averianov, Alexander O.; Sues, Hans-Dieter (2024-11-06). "New evidence for the presence of carcharodontosaurid theropod dinosaurs in the Late Cretaceous of Uzbekistan" (in en). Historical Biology: 1–7. doi:10.1080/08912963.2024.2423675. ISSN 0891-2963. https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2423675. 
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 Panteleev (1998). ""New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum." Russkii Ornitologicheskii Zhurnal". Ekspress-vy.PVSK 35: 3–15. 
  15. ↑ 15.0 15.1 15.2 "Table 11.1," in Weishampel, et al. (2004). Page 213.
  16. ↑ 16.0 16.1 "Table 11.1," in Weishampel, et al. (2004). Page 216.
  17. ↑ Kurochkin. (1996). "A new Enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves)." Russian Academy of Sciences, special issue: 50pp.
  18. ↑ "Table 11.1," in Weishampel, et al. (2004). Page 212.
  19. ↑ 19.0 19.1 19.2 "Table 11.1," in Weishampel, et al. (2004). Page 214.
  20. ↑ "Table 8.1," in Weishampel, et al. (2004). Page 166.
  21. ↑ Averianov, A. O.; Sues, H.-D. (2025). "A new ornithomimid theropod from the Upper Cretaceous Bissekty Formation of Uzbekistan". Journal of Vertebrate Paleontology: e2433759. doi:10.1080/02724634.2024.2433759. 
  22. ↑ "Table 10.1," in Weishampel, et al. (2004). Page 199.
  23. ↑ "Table 9.1," in Weishampel, et al. (2004). Page 185.
  24. ↑ Nesov, A. (1995). "Dinosaurs of Northern Eurasia: new data about assemblages, ecology and paleobiogeography." Scientific Research Institute of the Earth's Crust. St. Petersburg State University, St. Petersburg, Russia: 156 pp. + 14 pl. [in Russian with short English, German, and French abstracts].
  25. ↑ Sues, H.-D.; Averianov, A. (2016). "Therizinosauroidea (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan". Cretaceous Research 59: 155–178. doi:10.1016/j.cretres.2015.11.003. Bibcode: 2016CrRes..59..155S. 
  26. ↑ Stephen L. Brusatte; Alexander Averianov; Hans-Dieter Sues; Amy Muir; Ian B. Butler (2016). "New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs". Proceedings of the National Academy of Sciences of the United States of America 113 (13): 3447–3452. doi:10.1073/pnas.1600140113. PMID 26976562. Bibcode: 2016PNAS..113.3447B. 
  27. ↑ Averianov, A.O.; Sues, H.-D. (2007). "A new troodontid (Dinosauria: Theropoda) from the Cenomanian of Uzbekistan, with a review of troodontid records from the territories of the former Soviet Union". Journal of Vertebrate Paleontology 27 (1): 87–98. doi:10.1671/0272-4634(2007)27[87:ANTDTF2.0.CO;2]. 

Bibliography

Further reading



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