Bayan Shireh Formation

Bayan Shireh Formation Stratigraphic range: Late Cretaceous (Cenomanian-Santonian?)
Type	Geological formation
Sub-units	"Sheeregeen Gashoon" beds (upper Bayan Shireh)
Location
Region	Asia
Country	Mongolia

The Bayan Shireh Formation (also known as Bayanshiree Svita or the Baynshirenskaya Formation) is a geological formation in Burkhant, Mongolia, that dates to the late Cretaceous period. The exact age is uncertain, with two competing hypotheses; based on comparisons with other formations, the Bayan Shireh fauna seems to correspond best with the Turonian through early Campanian stages of the Late Cretaceous, about 93 to 80 million years ago.^[1] However, examination of the magnetostratigraphy of the formation seems to confirm that the entire Bayan Shireh lies within the Cretaceous Long Normal, which lasted only until the end of the Santonian stage, giving a possible Cenomanian through Santonian age, or between 98 and 83 million years ago.^[2] The fauna of this formation is similar to the nearby Iren Dabasu Formation.

Fauna

Theropod dinosaurs

Theropods reported from the Bayan Shireh Formation
Genus	Species	Location	Stratigraphic Position	Material	Notes	Images
Achillobator				"Partial skull and fragmentary postcrania."[3]	a giant dromaeosaur
Alectrosaurus					a tyrannosaur. Also present in the Iren Dabasu Formation
Enigmosaurus				"Incompletely preserved pelvis."[4]	a therizinosaur
Erlikosaurus				"Skull, pes, [and a] fragmentary postcranium."[4]	a therizinosaur
Garudimimus				"Skull with associated incomplete postcranium."[5]	an ornithomimosaur
Segnosaurus				"[Three] specimens, including mandible pelvis, hindlimb, scapulocoracoid, incomplete forelimb, [and] fragmentary vertebrae."[4]	a therizinosaur

Ornithischian dinosaurs

Ornithischians reported from the Bayan Shireh Formation
Genus	Species	Location	Stratigraphic Position	Material	Notes	Images
Amtosaurus	A. magnus			"Fragmentary skull."[6]
Graciliceratops			Sheeregeen Gashoon beds	"Partial skull, skeleton."[7]	A primitive ceratopsian, also present in the Minhe Formation
Maleevus			Sheeregeen Gashoon beds		an ankylosaur
Microceratus			Sheeregeen Gashoon beds		A primitive ceratopsian, also present in the Minhe Formation
Talarurus				"More than [five] specimens, including [two] partial skulls, nearly complete skeleton, osteoderms."[8]	an ankylosaur
Tsagantegia				"Skull."[8]	an ankylosaur

See also

• List of dinosaur-bearing rock formations

References

1. Jerzykiewicz, T. and Russell, D.A. (1991). "Late Mesozoic stratigraphy and vertebrates of the Gobi Basin." Cretaceous Research, 12(4): 345-377.
2. Hicks, J.F., Brinkman, D.L., Nichols, D.J., and Watabe, M. (1999). "Paleomagnetic and palynological analyses of Albian to Santonian strata at Bayn Shireh, Burkhant, and Khuren Dukh, eastern Gobi Desert, Mongolia." Cretaceous Research, 20(6): 829-850.
3. "Table 10.1," in Weishampel, et al. (2004). Page 198.
4. "Table 7.1," in Weishampel, et al. (2004). Page 152.
5. "Table 6.1," in Weishampel, et al. (2004). Page 138.
6. "Table 17.1," in Weishampel, et al. (2004). Page 367.
7. "Table 22.1," in Weishampel, et al. (2004). Page 480.
8. "Table 17.1," in Weishampel, et al. (2004). Page 364.