Iren Dabasu Formation

From Wikipedia, the free encyclopedia
Iren Dabasu Formation
Stratigraphic range: Cenomanian
~96 Ma
↓
TypeGeological formation
Unit of
Overlies
AreaErenhot (Erlian) city
ThicknessUp to 500 m (1,600 ft)
Lithology
PrimarySandstone, claystone, siltstone
OtherGlutenite
Location
Coordinates43°48′N 112°24′E / 43.8°N 112.4°E / 43.8; 112.4Coordinates: 43°48′N 112°24′E / 43.8°N 112.4°E / 43.8; 112.4
Approximate paleocoordinates43°06′N 101°00′E / 43.1°N 101.0°E / 43.1; 101.0
RegionInner Mongolia
Country China
Extent
Type section
Named forIren Dabasu
Named byOsborn
Year defined1922
Iren Dabasu Formation is located in China
Iren Dabasu Formation
Iren Dabasu Formation (China)

The Iren Dabasu Formation (also known as Erlian Formation) is a Late Cretaceous (Cenomanian) geologic formation in the Iren Nor region of Inner Mongolia. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation. The formation was first described and defined by Henry Fairfield Osborn in 1922 and it is located in the Iren Nor region of China.[1]

Geology[]

It comprises continental clastic sediments consisting of light grey fine sandstones, coarse sandstones and glutenites as well as mottled claystones and siltstones. The fine-grained floodplain sediments and the coarse-grained sediments of the point bar formed a series of repeated frequently binary sedimentary rhythms. The “binary structure” of the sedimentary rhythms strongly indicates meandering stream deposits rather than braided river deposits as previously thought.[2][3] As indicated by the fluvial and lacustrine sedimentation, the Iren Dabasu Formation was a large floodplain terrain with braided rivers and meanders that supported extensive vegetation, evidenced on the prominent palaeosol development and the numerous remains from herbivorous dinosaurs.[3][2] Egg nests, caliche and paleosols seem to indicate periodic subaerial intervals, in addition, the presence of plesiosaur and hybodont shark remains (which are also known in the Bayan Shireh Formation) are indicatives of a river system with connections to the ocean.[4]

Correlations[]

Based on the ostracod and charophyte assemblages of the Iren Dabasu Formation, Itterbeeck et al. 2005 suggested a potential correlation with those of the Nemegt Formation, making its age Late Campanian to Early Maastrichtian.[3] However, vertebrates point to an older date than the Campanian-Maastrichtian ages, the supposed deposition of ostracods is likely due to climatic conditions rather than age.[5] The turtle Khunnuchelys is known from both Iren Dabasu and Bayan Shireh equivalent units such as the Bostobe and Bissekty.[2] In addition, a giant caenagnathid similar to Gigantoraptor is now known from the Bayan Shireh Formation at the locality of Tsagan Teg.[5] Like the coeval Bayan Shireh Formation (and possibly Javkhlant Formation) in the Gobi Desert, the dinosaur fauna of the Iren Dabasu Formation includes tyrannosauroids, ornithomimids, therizinosaurs and oviraptorosaurs.[6]

However, strong evidence coming from biostratigraphic occurrences seems to support a correlation with the Bayan Shireh Formation, at least, with the upper boundary. For instance, both formations bear similar dinosaur taxa, such as therizinosaurs (Erlikosaurus, Segnosaurus, Erliansaurus or Neimongosaurus) and ornithomimosaurs (Garudimimus or Archaeornithomimus), these similarities are even more intensified by the discovery of Gigantoraptor and the giant unnamed caenagnathid from Bayan Shireh. In addition, the potential discovery of Alectrosaurus in both formations seems to be another indicative of a correlation.[7][2][5] Consequently, Averianov and Sues estimated the formation to be Santonian in age, roughly about 86 million and 83 million years ago.[2] Guo et al. 2018 also supported a Cenomanian age based on U–Pb, paleomagnetic and biostratigraphic analyses, around 95.8 ± 6.2 million years ago.[8]

Fossil content[]

The Iren Dabasu Formation is rich on dinosaur fauna, with multiple species described, in the other hand, mammals seem to be extremely absent. Compared, the fossil taxa between Iren Dabasu and Bayan Shireh are very similar, most notably therizinosaurs, tyrannosauroids, oviraptorosaurs and turtles.[9][2] Although Gigantoraptor is the only described oviraptorosaur from the formation, Funston et al. 2019 described a new avimimid bonebed containing numerous individuals at different growth stages. Nevertheless, the fossils lacked enough diagnosis to be confined to a separate genus and species.[4] Deinonychosaurs are not very common across the formation, however an indeterminate troodontid about the size of Saurornithoides is known from three isolated specimens.[10]

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.

Dinosaurs[]

Theropods[]

Theropods reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

Alectrosaurus

A. olseni

"Virtually complete right hindlimb and left metatarsals."[11]

A tyrannosauroid. Potentially present in the Bayan Shireh Formation

Alectrosaurus.png

Archaeornithomimus

A. asiaticus

"Partial manus, metatarsus, vertebrae, limb elements."[11]

An ornithomimosaur originally identified as Ornithomimus.

Archaeornithomimus.png

Avimimidae spp.

Indeterminate

"Vertebrae and postcranial elements represented by at least six individuals."[4]

Avimimids at different growth stages.

Iren Dabasu avimimid skeleton.png

Caenagnathasia spp.

Indeterminate

"Beak from lower jaws."[12]

An oviraptorosaur.

Caenagnathasia.jpg

Erliansaurus

E. bellamanus

"Cervical vertebrae and postcranial elements."[13]

A therizinosauroid.

Erliansaurus bellamanus.jpg

Gigantoraptor

G. erlianensis

"Lower jaws and much of the postcranial elements with very elongated hindlimbs."[14]

A giant oviraptorosaur.

Gigantoraptor Restoration.png

Neimongosaurus

N. yangi

"Two specimens with most of the axial column, many limb and girdle elements, and a partial dentary."[15]

A therizinosauroid.

Neimongosaurus.jpg

Therizinosauridae spp.

Indeterminate

"Right humerus with a phalanx and ungual."[11][16]

A therizinosaurid similar to Segnosaurus.

AMNH 6368 Therizinosaur.png

Troodontidae spp.

Indeterminate

"Right and left metatarsals represented by three specimens."[10]

A troodontid.

Ornithopods[]

Ornithopods reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

Bactrosaurus

B. johnsoni

"Cranial and postcranial material represented by more than eight specimens."[11][17][18]

A hadrosauroid.

Bactrosaurus.JPG

Gilmoreosaurus

G. mongoliensis

"Partial cranial and postcranial elements represented by more than ten specimens".[11][19][18]

A hadrosauroid originally identified as Mandschurosaurus.

Dans l'ombre des dinosaures - Gilmareasaurus - 001.jpg

Spheroolithus

S. irenensis

"Egg fossils."[20]

Eggs shells attributed to Spheroolithus. Spheroolithidae cropped.jpg

Sauropods[]

Sauropods reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

Sonidosaurus

S. saihangaobiensis

"Numerous cervical, dorsal and caudal vertebrae and some postcranial elements."[21]

A titanosaur.

Sonidosaurus.jpg

Flora[]

Angiosperms[]

Angiosperms reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

Aquillapollenites sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

sp.

Indeterminate "Spores and pollen."[22]

Angiosperm pollen.

sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

Normapolles sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

Tricolpate-morph

Indeterminate "Pollen grain."[22]

Angiosperm palynomorph.

-morph

Indeterminate "Pollen grain."[22]

Angiosperm palynomorph.

sp.

Indeterminate "Pollen grain."[22]

Angiosperm pollen.

sp.

Indeterminate "Spores and pollen."[22]

Angiosperm pollen.

Gymnosperms[]

Gymnosperms reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

-morph

Indeterminate "Spores and pollen."[22]

Gymnosperm palynomorph.

sp.

Indeterminate "Pollen grain."[22]

Gymnosperm pollen.

-morph

Indeterminate "Pollen grain."[22]

Gymnosperm palynomorph.

sp.

Indeterminate "Spores and pollen."[22]

Gymnosperm pollen.

sp.

Indeterminate "Spores and pollen."[22]

Gymnosperm pollen.

Monosulcate-morph

Indeterminate "Pollen grain."[22]

Gymnosperm pollen.

sp.

Indeterminate "Pollen grain."[22]

Gymnosperm pollen.

Spores[]

Spores reported from the Iren Dabasu Formation
Genus Species Location Stratigraphic Position Material Notes Images

sp.

Indeterminate "Spores and pollen grain."[22]

Spore palynomorph.

sp.

Indeterminate "Spores."[22]

Spore palynomorph.

sp.

Indeterminate "Spores."[22]

Spore palynomorph.

sp.

Indeterminate "Spores."[22]

Spore palynomorph.

See also[]

References[]

  1. ^ Osborn, H. F. (1922). "Discovery of Cretaceous and older Tertiary strata in Mongolia" (PDF). Science. 56 (1446): 291–293. doi:10.1126/science.56.1446.291. PMID 17842026.
  2. ^ a b c d e f Averianov, A.; Sues, H. (2012). "Correlation of Late Cretaceous continental vertebrate assemblages in Middle and Central Asia" (PDF). Journal of Stratigraphy. 36 (2): 462–485. Archived from the original (PDF) on 2019-03-07.
  3. ^ a b c Van Itterbeeck, J.; Horne, D. J.; Bultynck, P.; Vandenberghe, N. (2005). "Stratigraphy and palaeoenvironment of the dinosaur-bearing Upper Cretaceous Iren Dabasu Formation, Inner Mongolia, People's Republic of China". Cretaceous Research. 26 (4): 699–725. doi:10.1016/j.cretres.2005.03.004.
  4. ^ a b c Funston, G. F.; Currie, P. J.; Ryan, M. J.; Dong, Z.-M. (2019). "Birdlike growth and mixed-age flocks in avimimids (Theropoda, Oviraptorosauria)". Scientific Reports. 9 (18816). doi:10.1038/s41598-019-55038-5. PMC 6906459. PMID 31827127.
  5. ^ a b c Tsuihiji, T.; Watabe, M.; Barsbold, R.; Tsogtbaatar, K. (2015). "A gigantic caenagnathid oviraptorosaurian (Dinosauria: Theropoda) from the Upper Cretaceous of the Gobi Desert, Mongolia". Cretaceous Research. 56: 60–65. doi:10.1016/j.cretres.2015.03.007.
  6. ^ Xing, H.; He, Y.; Li, L.; Xi, D. (2012). "A review on the study of the stratigraphy, sedimentology, and paleontology of the Iren Dabasu Formation, Inner Mongolia". In Wei, D. (ed.). Proceedings of the Thirteenth Annual Meeting of the Chinese Society of Vertebrate Paleontology (in Chinese). Beijing: China Ocean Press. pp. 1–44.
  7. ^ Perle, A. (1977). "O pervoy nakhodke Alektrozavra (Tyrannosauridae, Theropoda) iz pozdnego Mela Mongolii" [On the first discovery of Alectrosaurus (Tyrannosauridae, Theropoda) in the Late Cretaceous of Mongolia]. Shinzhlekh Ukhaany Akademi Geologiin Khureelen (in Russian). 3 (3): 104–113.
  8. ^ Guo, Z. X.; Shi, Y. P.; Yang, Y. T.; Jiang, S. Q.; Li, L. B.; Zhao, Z. G. (2018). "Inversion of the Erlian Basin (NE China) in the early Late Cretaceous: Implications for the collision of the Okhotomorsk Block with East Asia" (PDF). Journal of Asian Earth Sciences. 154: 49–66. doi:10.1016/j.jseaes.2017.12.007.
  9. ^ Currie, P. J.; Eberth, D. A. (1993). "Palaeontology, sedimentology and palaeoecology of the Iren Dabasu Formation (Upper Cretaceous), Inner Mongolia, People's Republic of China". Cretaceous Research. 14 (2): 127−144. doi:10.1006/cres.1993.1011.
  10. ^ a b Currie, P. J.; Zhiming, D. (2001). "New information on Cretaceous troodontids (Dinosauria, Theropoda) from the People's Republic of China". Canadian Journal of Earth Sciences. 38 (12): 1753–1766. doi:10.1139/e01-065.
  11. ^ a b c d e Gilmore, C. W. (1933). "On the dinosaurian fauna of the Iren Dabasu Formation". Bulletin of the American Museum of Natural History. 67 (2): 23–78. hdl:2246/355.
  12. ^ Yao, X.; Wang, X. L.; Sullivan, C.; Wang, S.; Stidham, T.; Xu, X. (2015). "Caenagnathasia sp. (Theropoda: Oviraptorosauria) from the Iren Dabasu Formation (Upper Cretaceous: Campanian) of Erenhot, Nei Mongol, China" (PDF). Vertebrata PalAsiatica. 53 (4): 291–298.
  13. ^ Xu, X.; Zhang, Z. H.; Sereno, P. C.; Zhao, X. J.; Kuang, X. W.; Han, J.; Tan, L. (2002). "A new therizinosauroid (Dinosauria, Theropoda) from the Upper Cretaceous Iren Dabasu Formation of Nei Mongol" (PDF). Vertebrata PalAsiatica. 40: 228–240.
  14. ^ Xing, X.; Tan, Q.; Wang, J.; Zhao, X.; Tan, L. (2007). "A gigantic bird-like dinosaur from the Late Cretaceous of China". Nature. 447 (7146): 844–847. doi:10.1038/nature05849. PMID 17565365. Supplementary Information
  15. ^ Zhang, X. H.; Xu, X.; Zhao, Z. J.; Sereno, P. C.; Kuang, X. W.; Tan, L. (2001). "A long-necked therizinosauroid dinosaur from the Upper Cretaceous Iren Dabasu Formation of Nei Mongol, People's Republic of China" (PDF). Vertebrata PalAsiatica. 39 (4): 282–290.
  16. ^ Mader, B. J.; Bradley, R. L. (1989). "A redescription and revised diagnosis of the syntypes of the Mongolian tyrannosaur Alectrosaurus olseni". Journal of Vertebrate Paleontology. 9 (1): 41–55. doi:10.1080/02724634.1989.10011737.
  17. ^ Godefroit, P.; Dong, Z. M.; Bultynck, P.; Li., H.; Feng, L. (1998). "New Bactrosaurus (Dinosauria: Hadrosauroidea) material from Iren Dabasu (Inner Mongolia, P.R. China)". Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre. 68: 3–70.
  18. ^ a b Rothschild, B. M.; Tanke, D. H.; Helbling II, M.; Martin, L. D. (2003). "Epidemiologic study of tumors in dinosaurs". Naturwissenschaften. 90 (11): 495–500. doi:10.1007/s00114-003-0473-9. PMID 14610645.
  19. ^ Prieto-Márquez, A.; Norell, M. A. (2010). "Anatomy and relationships of Gilmoreosaurus mongoliensis (Dinosauria, Hadrosauroidea) from the late Cretaceous of Central Asia". American Museum Novitates (3694): 1–49. hdl:2246/6080.
  20. ^ Chao, T. K.; Chiang, T. K. (1974). "Microscopic studies on the dinosaurian egg-shells from Laiyang, Shanting province". Scientia Sinica. 17 (11): 73−90.
  21. ^ Xu, X.; Zhang, X.; Tan, Q.; Zhao, X.; Tan, L. (2010). "A new titanosaurian sauropod from Late Cretaceous of Nei Mongol, China". Acta Geologica Sinica. 80 (1): 20–26. doi:10.1111/j.1755-6724.2006.tb00790.x.
  22. ^ a b c d e f g h i j k l m n o p q r s t u Bonnetti, C.; Malartre, F.; Huault, V.; Cuney, M.; Bourlange, S.; Liu, X.; Peng, Y. (2014). "Sedimentology, stratigraphy and palynological occurrences of the late Cretaceous Erlian Formation, Erlian Basin, Inner Mongolia, People's Republic of China". Cretaceous Research. 48: 177–192. doi:10.1016/j.cretres.2013.09.013.
Retrieved from ""