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Ilek Formation

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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]

Ilek Formation
Stratigraphic range: Lower Cretaceous,
Barremian–Aptian
Shestakovo 3 locality
TypeGeological formation
Unit ofKiya River Basin
UnderliesKiya Formation
OverliesTyazhin Formation
ThicknessUp to 746 metres (2,450 ft)
Lithology
PrimaryClay, siltstone
OtherMarl, sandstone
Location
Coordinates55°54′N 88°00′E / 55.9°N 88.0°E / 55.9; 88.0
Approximate paleocoordinates54°12′N 84°36′E / 54.2°N 84.6°E / 54.2; 84.6
RegionWestern Siberia
Country Russia
Extent Kemerovo Oblast
Type section
Named byL. A. Ragozin
Year defined1935
Ilek Formation is located in Russia
Ilek Formation
Ilek Formation (Russia)
Ilek Formation is located in Kemerovo Oblast
Ilek Formation
Ilek Formation (Kemerovo Oblast)

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

 
View of Shestakovo 1 outcrops (upper left corner) from the Kiya River

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

Amphibians

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

Mammaliamorphs

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

Choristoderes

Choristoderes reported from the Ilek Formation
Taxon Locality Material Notes Images
cf. Khurendukhosaurus[18]
  • 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 indet.[18]
  • Smolenskii Yar
 Cervical centrum May represent a taxon distinct from both Khurendukhosaurus and the Shestakovo choristodere

Lizards

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

Turtles

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

Crocodylomorphs

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

Pterosaurs

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

Dinosaurs

Theropods reported from the Ilek Formation
Taxon Locality Material Notes Images
Evgenavis nobilis[23] A set of limb elements A confuciusornithiform
 
Kiyacursor longipes[24]
  • Shestakovo 1
 Partial skeleton including cervical and caudal vertebrae, cervical and dorsal ribs, a left scapulocoracoid, humeri, and much of both hind limbs[24] A noasaurid theropod
 
Paraves indet.[25] Teeth May belong to either Microraptorinae or Troodontidae
Mystiornis cyrili[26]
  • Shestakovo 1
 Isolated metatarsus An avisaurid enantiornithean
 
Paraves indet.[25] Teeth May belong to either Microraptorinae or Troodontidae
Theropoda indet.[27]
  • Shestakovo 1
 Partial cervical vertebra A long-necked theropod, possibly similar to basal therizinosauroids like Falcarius
Tyrannosauroidea indet.[25] Teeth
cf. Urbacodon sp.[25] Teeth A troodontid with unserrated teeth
Sauropodomorphs reported from the Ilek Formation
Taxon Locality Material Notes Images
Lithostrotia indet.[28] Caudal vertebrae Potentially three distinct taxa of titanosaur
Sibirotitan astrosacralis[5]
  • Shestakovo 1
  • Shestakovo 3[29]
 Vertebrae, sacrum, and pedal elements A somphospondylan sauropod
 
Ornithischians reported from the Ilek Formation
Taxon Locality Material Notes Images
Ornithischia indet.[4]
  • Shestakovo 1
  • Bol'shoi Kemchug 3
 Isolated teeth Originally identified as two distinct "hypsilophodontid" taxa[30]
Psittacosaurus sibiricus[31]
  • Shestakovo
 Several skeletons A ceratopsian
 
Stegosauria indet.[13]
  • Bol'shoi Kemchug 3
 Isolated teeth[30]

See also

References

  1. ^ a b c Golovneva, L. B.; Shchepetov, S. V. (April 2010). "Phytostratigraphy of Albian-Cenomanian sediments in the Kiya River basin (the Chulym-Yenisei area of the west Siberian lowland)". Stratigraphy and Geological Correlation. 18 (2): 153–165. Bibcode:2010SGC....18..153G. doi:10.1134/s0869593810020048. ISSN 0869-5938. S2CID 140540821.
  2. ^ Криштофович А. Н., ed. (1955). "Илекская свита". Геологический словарь. Vol. 1 (А-Л). p. 271. ISBN 9785458366533.
  3. ^ Лебедев И. В., ed. (1962). Биостратиграфия мезозойских и третичных отложений Западной Сибири. pp. 168–169.
  4. ^ a b c d e Ivantsov, S. V.; Fayngerts, A. V.; Feofanova, O. A.; Vladimirova, O. N.; Slobodin, D. A. (2024). "Early Cretaceous continental sedimentatary environments, palaeogeography and biota of southeastern Western Siberia". Geological Society, London, Special Publications. 545. doi:10.1144/SP545-2023-62.
  5. ^ a b Averianov, Alexander; Ivantsov, Stepan; Skutschas, Pavel; Faingertz, Alexey; Leshchinskiy, Sergey (2018). "A new sauropod dinosaur from the Lower Cretaceous Ilek Formation, Western Siberia, Russia". Geobios. 51 (1): 1–14. Bibcode:2018Geobi..51....1A. doi:10.1016/j.geobios.2017.12.004. ISSN 0016-6995.
  6. ^ Bugdaeva, E V; Markevich, V S; Volynets, E B (2017). "Palaeoenvironmental and palaeoclimatic reconstruction of the Early Cretaceous psittacosaur localities, Asia". Proceedings and Field Guidebook for the Fifth International Symposium of International Geoscience Programme IGCP Project 608. Fifth International Symposium of International Geoscience Programme. Jeju Island, Korea. pp. 31–34.
  7. ^ Skutschas, P. P. (2014). "Kiyatriton leshchinskiyi Averianov et Voronkevich, 2001, a crown-group salamander from the Lower Cretaceous of Western Siberia, Russia". Cretaceous Research. 51: 88–94. doi:10.1016/j.cretres.2014.05.014. ISSN 0195-6671.
  8. ^ Skutschas, P.; Kolchanov, V.; Anpilogova, E.; Parakhin, I.; Averianov, A.; Jones, M. (2023). "The last of them? A new relic karaurid stem salamander from the Lower Cretaceous of Western Siberia, Russia". Biological Communications. 68 (4): 219–226. doi:10.21638/spbu03.2023.402.
  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 Averianov, A. O.; Skutschas, P. P.; Lopatin, A. V.; Leshchinskiy, S. V.; Rezvyi, A. S.; Fayngerts, A. V. (2005). "Early Cretaceous mammals from Bol'shoi Kemchug 3 locality in West Siberia, Russia". Russian Journal of Theriology. 4 (1): 1–12. doi:10.15298/rusjtheriol.04.1.01.
  14. ^ E. N. Maschenko and A. V. Lopatin. 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386:475-477
  15. ^ "Fossilworks: Stereognathus".
  16. ^ a b Lopatin, A. V.; Averianov, A. O.; Ivantsov, S. V.; Kuzmin, I. T.; Skutschas, P. P. (2023-07-19). "An Upper Molar of a Docodontan (Docodonta, Mammaliaformes) from the Lower Cretaceous of Western Siberia". Doklady Earth Sciences. doi:10.1134/S1028334X23601128. ISSN 1028-334X.
  17. ^ Maschenko, E. N.; Lopatin, A. V.; Voronkevich, A. V. (2002). "A new genus of the tegotheriid docodonts (Docodonta, Tegotheriidae) from the Early Cretaceous of West Siberia". Russian Journal of Theriology. 1 (2): 75–81. doi:10.15298/rusjtheriol.01.2.01.
  18. ^ a b c Skutschas, Pavel P.; Vitenko, Dmitriy D. (2017-05-04). "Early Cretaceous choristoderes (Diapsida, Choristodera) from Siberia, Russia". Cretaceous Research. 77: 79–92. Bibcode:2017CrRes..77...79S. doi:10.1016/j.cretres.2017.05.004. ISSN 0195-6671.
  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. ^ Averianov, Alexander O.; Ivantsov, Stepan V.; Leshchinskiy, Sergey V.; Skutschas, Pavel P. (2022-09-01). "First pterosaur bone from the Lower Cretaceous of Siberia, Russia". Cretaceous Research. 137: 105230. Bibcode:2022CrRes.13705230A. doi:10.1016/j.cretres.2022.105230. ISSN 0195-6671. S2CID 248136173.
  22. ^ Skutschas, P. (2006). "Mesozoic amphibians from Siberia, Russia". 9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota, Abstracts and Proceedings Volume: 123–126.
  23. ^ 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.
  24. ^ a b Averianov, A. O.; Skutschas, P. P.; Atuchin, A. A.; Slobodin, D. A.; Feofanova, O. A.; Vladimirova, O. N. (2024). "The last ceratosaur of Asia: a new noasaurid from the Early Cretaceous Great Siberian Refugium". Proceedings of the Royal Society B: Biological Sciences. 291 (2023). 20240537. doi:10.1098/rspb.2024.0537.
  25. ^ a b c d Averianov, A.O.; Ivantsov, S.V.; Skutschas, P.P. (2019-06-25). "Theropod teeth from the Lower Cretaceous Ilek Formation of Western Siberia, Russia". Proceedings of the Zoological Institute of the Russian Academy of Sciences (in Russian). 323 (2): 65–84. doi:10.31610/trudyzin/2019.323.2.65. ISSN 0206-0477.
  26. ^ 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.
  27. ^ Averianov, Alexander O.; Lopatin, Alexey V. (2023-07-10). "A long-necked theropod from the Lower Cretaceous of Western Siberia, Russia". Journal of Vertebrate Paleontology. doi:10.1080/02724634.2023.2216761. ISSN 0272-4634.
  28. ^ Alexander O. Averianov; Stepan V. Ivantsov; Pavel P. Skutschas (2020). "Caudal vertebrae of titanosaurian sauropod dinosaurs from the Lower Cretaceous Ilek Formation in Western Siberia, Russia". Cretaceous Research. 107: Article 104309. Bibcode:2020CrRes.10704309A. doi:10.1016/j.cretres.2019.104309. S2CID 210619334.
  29. ^ Averianov, A.; Podlesnov, A.; Slobodin, D.; Skutschas, P.; Feofanova, O.; Vladimirova, O. (2023). "First sauropod dinosaur remains from the Early Cretaceous Shestakovo 3 locality, Western Siberia, Russia". Biological Communications. 68 (4): 236–252. doi:10.21638/spbu03.2023.404.
  30. ^ a b Averianov, A. O.; Leshchinskiy, S. V.; Skutschas, P. P.; Fayngertz, A. V.; Rezvyi, A. S. (2004). "Dinosaurs from the Early Cretaceous Ilek Formation in West Siberia, Russia". Second European Association of Vertebrate Paleontologists Meeting. Abstracts of Papers. 6: 6.
  31. ^ 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.
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