Coordinates: 55°54′N 88°00′E / 55.9°N 88.0°E / 55.9; 88.0

Ilek Formation

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Ilek Formation
Stratigraphic range: Lower Cretaceous,
Barremian–Aptian
File:Shestakovsky Yar.jpg
Shestakovo 1 locality
TypeGeological formation
Unit ofKiya River Basin
UnderliesKiya Formation
OverliesTyazhin Formation
ThicknessUp to 746 metres (2,450 ft)
Lithology
PrimaryClay, siltstone
OtherMarl, sandstone
Location
CoordinatesLua error in Module:Coordinates at line 489: attempt to index field 'wikibase' (a nil value).
Approximate paleocoordinatesLua error: callParserFunction: function "#coordinates" was not found.
RegionWestern Siberia
CountryRussia
ExtentKemerovo Oblast
Type section
Named byL. A. Ragozin
Year defined1935
Ilek Formation (Russia)
Ilek Formation (Kemerovo Oblast)

The Ilek Formation is a Lower Cretaceous geologic formation in Western Siberia. Many different fossils have been recovered from the formation. It overlies the Late Jurassic Tyazhin Formation and underlies the Albian Kiya Formation.[1]

The formation was described by L. A. Ragozin in 1935. It consists of sands with sandstone concretions, layers of silts, clays and marls.[2] Age of the formation, according to a crude 1962 estimate, is Valanginian(?) - Hauterivian - Barremian. Its thickness varies greatly, reaching 746 m in Teguldet borehole.[3] A more recent 2024 estimate based on invertebrate and vertebrate fossils placed the age of the formation at Barremian–Aptian.[4]

Age

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File:Shestakovo 3.jpg
Shestakovo 3 locality

The Ilek Formation conformably overlies the Upper Jurassic Tyazhin Formation.[1] Gastropods and bivalves of Valanginian age have been recovered from the lower part of the formation, and gastropods and bivalves of Hauterivian to Barremian age have been found in the upper part, as well as Barremian ostracods. The age of the Shestakovo 1 locality is poorly constrained.[5] Palynological samples from the Shestakovo 3 locality are characteristic of the Aptian. No angiosperm pollen has been found at this locality, indicating that it is older than the Albian.[6] The upper layers of the formation do contain angiosperm pollen, indicating that part of the formation may extend into the Albian. The overlying Kiya Formation is upper Albian based on plant biostratigraphy.[1]

Fauna

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Amphibians

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Amphibians reported from the Ilek Formation
Genus Species Locality Material Notes Images
Kiyatriton K. leshchinskiyi[7]
  • Shestakovo 1
 Atlas, trunk vertebrae, fragmentary dentaries, femora, humerus, and nearly complete ilium A crown-group salamander
Kuzbassia K. sola[8]
  • Shestakovo 1
 Two atlantal centra and a trunk vertebral centrum A karaurid

Mammaliamorphs

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Mammaliamorphs reported from the Ilek Formation
Genus Species Locality Material Notes Images
Acinacodus A. tagaricus[9] Right dentary fragment An amphidontid mammal
Baidabatyr B. clivosus[10]
  • Bol'shoi Kemchug 3
 Upper premolar A multituberculate
Gobiconodon G. borissiaki[11] 21 upper and lower jaws. A gobiconodont
G. hoburensis[12] A fragmentary lower jaw.
Kemchugia K. magna[13] A tooth An amphilestid mammal
Kiyatherium K. cardiodens[14] A maxilla A zhangheotheriid mammal
Sibirotherium S. rossicum[15]
  • Bol'shoi Kemchug 4
 M1 tooth;[15] mandibular fragments[16] A docodontan mammaliaform
Xenocretosuchus X. sibiricus[17] Dental elements A tritylodontid mammaliamorph
Yermakia Y. domitor[13]
  • Shestakovo 1
 A mandible A tinodontid mammal

Choristoderes

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Choristoderes reported from the Ilek Formation
Genus Species Locality Material Notes Images
cf. Khurendukhosaurus[18] K. cf. sp
  • Bol'shoi Kemchug 3
 Dorsal vertebra, sacral vertebra A non-neochoristodere choristodere
"Shestakovo choristodere"[18]
  • Shestakovo
  • Bol'shoi Kemchug 3
  • Bol'shaya Terekhtul' 2
 Fragmentary dentaries, several vertebrae, rib fragments A possible neochoristodere
Choristodera[18] Indeterminate
  • Smolenskii Yar
 Cervical centrum May represent a taxon distinct from both Khurendukhosaurus and the "Shestakovo choristodere"

Lizards

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Lizards reported from the Ilek Formation
Genus Species Locality Material Notes Images
Paramacellodidae Indeterminate[4]
  • Kemchug assemblage
  • Kiya assemblage
Platynota Indeterminate[4]
  • Kemchug assemblage
Xenosauridae Indeterminate[4]
  • Kemchug assemblage
  • Kiya assemblage
 A knob-scaled lizard

Turtles

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Turtles reported from the Ilek Formation
Genus Species Locality Material Notes Images
Kirgizemys A macrobaenid

Crocodylomorphs

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Crocodylomorphs reported from the Ilek Formation
Genus Species Locality Material Notes Images
Kyasuchus K. saevi[19]
  • Shestakovo 3
 A partial skull A shartegosuchid crocodyliform
Tagarosuchus T. kulemzini[20]
  • Shestakovo 3
 Nearly complete skull A crocodyliform

Pterosaurs

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Pterosaurs reported from the Ilek Formation
Genus Species Locality Material Notes Image
?Ctenochasmatidae Indeterminate[13]
  • Bol'shoi Kemchug 3
Lonchognathosaurus L. cf. sp.[21]
  • Novochernorechensk
 Wing metacarpal fragment A dsungaripterid
Ornithocheiridae Indeterminate[22]
  • Shestakovo 1
Pterodactyloidea Indeterminate[13]
  • Bol'shoi Kemchug 3

Dinosaurs

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Sauropodomorphs

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Sauropodomorphs reported from the Ilek Formation
Genus Species Locality Material Notes Images
Lithostrotia Indeterminate[23] Caudal vertebrae Potentially three distinct taxa of titanosaur
Sibirotitan S. astrosacralis[5]
  • Shestakovo 1
  • Shestakovo 3[24]
 Vertebrae, sacrum, and pedal elements A somphospondylan sauropod
File:Sibirotitan model.jpg

Ornithischians

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Ornithischians reported from the Ilek Formation
Genus Species Locality Material Notes Images
Ornithischia Indeterminate[4]
  • Shestakovo 1
  • Bol'shoi Kemchug 3
 Isolated teeth Originally identified as two distinct "hypsilophodontid" taxa[25]
Psittacosaurus P. sibiricus[26]
  • Shestakovo
 Several skeletons A ceratopsian
File:Psittacosaurus sibiricus.png
Stegosauria Indeterminate[13]
  • Bol'shoi Kemchug 3
 Isolated teeth[25]

Theropods

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Theropods reported from the Ilek Formation
Genus Species Locality Material Notes Images
Evgenavis E. nobilis[27] A set of limb elements A confuciusornithiform
File:Evgenavis tarsometatarsus.png
Kiyacursor K. longipes[28]
  • Shestakovo 1
 Partial skeleton including cervical and caudal vertebrae, cervical and dorsal ribs, a left scapulocoracoid, humeri, and much of both hind limbs[28] A noasaurid theropod
File:Kiyacursor PM (white bg).png
Paraves Indeterminate[29] Teeth May belong to either Microraptorinae or Troodontidae
Mystiornis M. cyrili[30]
  • Shestakovo 1
 Isolated metatarsus An avisaurid enantiornithean
File:Mystiornis.png
Paraves Indeterminate[29] Teeth May belong to either Microraptorinae or Troodontidae
Tyrannosauroidea Indeterminate[29] Teeth
Urbacodon U. cf. sp.[29] Teeth A troodontid with unserrated teeth

See also

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References

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  1. ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  9. ^ A. V. Lopatin; E. N. Maschenko & A. O. Averianov (2010). "A new genus of triconodont mammals from the Early Cretaceous of Western Siberia". Doklady Biological Sciences. 433 (1): 282–285. doi:10.1134/S0012496610040137.
  10. ^ Alexander Averianov; Alexey Lopatin; Pavel Skutschas; Stepan Ivantsov; Elizaveta Boitsova; Ivan Kuzmin (2017). "An enigmatic multituberculate mammal from the Early Cretaceous of Siberia, Russia". Journal of Vertebrate Paleontology. 37 (2): e1293070. doi:10.1080/02724634.2017.1293070.
  11. ^ Trofimov, B. A. (1978). "The first triconodonts (Mammalia, Triconodonta) from Mongolia". Doklady Akademii Nauk SSSR. 243 (1): 213–216.
  12. ^ Maschenko, E. N.; Lopatin, A. V. (1998). "First record of an Early Cretaceous triconodont mammal in Siberia". Bull. Inst. R. Sci. Nat. Belg. 68: 233–236.
  13. ^ a b c d e Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  14. ^ E. N. Maschenko and A. V. Lopatin. 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386:475-477
  15. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  16. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  18. ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  19. ^ Efimov, M. B. and Leshchinskiy, S. V. (2000). First finding of the fossil crocodile skull in Siberia [in Russian]. In: Komarov, A. V., ed., Materialy regional’noj konferencii geologov Sibiri, Dal’nego Vostoka i Severo−Vostoka Rossii. Tom II, 361–363. GalaPress, Tomsk.
  20. ^ Fiorelli, L.E.; Calvo, J.O. (2007). "The first "protosuchian" (Archosauria: Crocodyliformes) from the Cretaceous (Santonian) of Gondwana" (PDF).
  21. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  26. ^ Averianov, Alexander O.; Voronkevich, Alexei V.; Leshchinskiy, Sergei V.; Fayngertz, Alexei V. (2006). "A ceratopsian dinosaur Psittacosaurus sibiricus from the Early Cretaceous of West Siberia, Russia and its phylogenetic relationships". Journal of Systematic Palaeontology. 4 (4): 359–395. doi:10.1017/s1477201906001933.
  27. ^ O'Connor, JL; Averianov, AO; Zelenkov, NV (2014). "A confuciusornithiform (Aves, Pygostylia)-like tarsometatarsus from the Early Cretaceous of Siberia and a discussion of the evolution of avian hind". Journal of Vertebrate Paleontology. 34 (3): 647–656. doi:10.1080/02724634.2013.828734.
  28. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  29. ^ a b c d Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  30. ^ Evgeny N. Kurochkin; Nikita V. Zelenkov; Alexandr O. Averianov; Sergei V. Leshchinskiy (2011). "A new taxon of birds (Aves) from the Early Cretaceous of Western Siberia, Russia". Journal of Systematic Palaeontology. 9 (1): 109–117. doi:10.1080/14772019.2010.522202.
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