Öösh Formation

The Öösh Formation, also known as the Tevsh Formation or Hühteeg Svita, is a geological formation of Lower Cretaceous strata in Mongolia. Dinosaur remains are among the fossils that have been recovered from the formation.[1] It overlies folded and metamorphosed basement strata of the Gobi region, and is capped by basalt. The succession is around 600 metres thick and consists of red claystones and sandstones, along with black thinly laminated shales. The claystones and sandstones were deposited as part of an alluvial fan system, while the shales were deposited in lakes present in the foot of the fan.[2] Many of the fossils come from the "Cannonball beds", which comprise the lowest 60 metres of the unit and consist of green siltstone.[2]

Öösh Formation Stratigraphic range: Berriasian-Barremian ~141–125 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Sub-units	Cannonball beds
Underlies	Basalt
Overlies	Basement
Thickness	600 m (2,000 ft)
Lithology
Primary	Sandstone, claystone, shale
Other	Siltstone
Location
Coordinates	44.2°N 102.7°E / 44.2; 102.7
Approximate paleocoordinates	45.0°N 103.3°E / 45.0; 103.3
Region	Ovorkhangai
Country	Mongolia
Öösh Formation (Mongolia)

Vertebrate paleofauna

Dinosaurs

Dinosaurs of the Öösh Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Asiatosaurus	A. mongoliensis			Teeth	Indeterminate sauropod
Prodeinodon	P. mongoliensis			Several teeth, fragmentary tibia, fragmentary fibula	Indeterminate theropod
Protiguanodon	P. mongoliensis				Reclassified as a species of Psittacosaurus, Psittacosaurus protiguanodonensis
Psittacosaurus	P. mongoliensis					Psittacosaurus fossil from the Hühteeg Svita with gastroliths in its stomach region, American Museum of Natural History
	P. protiguanodonensis				Junior synonym of P. mongoliensis
Shanag[3]	S. ashile[3]

Mammals

Mammals of the Öösh Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Gobiconodon[4]	G. hopsoni[4]		Cannonball Member of Öösh Formation, possibly equivalent of Tevsh Formation	Two upper and lower jaws (PSS-MAE 140 (Holotype) & PSS-MAE 139)

Pterosaurs

Pterosaurs of the Öösh Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Indeterminate Tapejaroid[2]				"Single vertebra"[2]

Squamates

Squamates of the Öösh Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Norellius[5]	N. nyctisaurops			"Nearly complete skull with mandibles and partial hyoid"	Gekkonomorph

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.

See also

• List of dinosaur-bearing rock formations

References

1. Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 563-570. ISBN 0-520-24209-2.
2. Andres, B. and Norell, M.A. 2005. The first record of a pterosaur from the Early Cretaceous strata of Öösh (Övörkhangai; Mongolia). American Museum Novitates 3472: 1–6.
3. Turner, A.S.; Hwang, S.H.; Norell, M.A. (2007). "A small derived theropod from Öösh, Early Cretaceous, Baykhangor Mongolia" (PDF). American Museum Novitates. 3557 (1): 1–27. doi:10.1206/0003-0082(2007)3557[1:ASDTFS]2.0.CO;2. hdl:2246/5845. Retrieved 2007-03-29.
4. Kielan-Jaworowska, Z., Dashzeveg, D. (1998). "Early Cretaceous amphilestid ("triconodont") mammals from Mongolia" (PDF). Acta Palaeontologica Polonica. 43 (3): 413–438.CS1 maint: multiple names: authors list (link)
5. Conrad, Jack L.; Daza, Juan D. (2015-08-28). "Naming and rediagnosing the Cretaceous gekkonomorph (Reptilia, Squamata) from Öösh (Övörkhangai, Mongolia)". Journal of Vertebrate Paleontology. 35 (5): e980891. doi:10.1080/02724634.2015.980891. ISSN 0272-4634.