Djadochta Formation

Djadochta Formation Stratigraphic range: Late Cretaceous (late Santonian?–early Campanian)
Type	Geological formation
Lithology
Primary	Sandstone
Location
Region	Asia
Country	Mongolia

The Djadochta Formation (sometimes transcribed Djadokhta) is situated in central Asia (Gobi Desert) and dates from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 84-75 mya (million years ago). The type locality are the famous "Flaming Cliffs", locally known as Bayanzag ("rich in Haloxylon") or Ulaan-Ereg ("red cliffs").

It preserves an arid habitat of sand dunes, with little freshwater apart from oases and arroyos. In fact, the present-day climate at most Djadochta Formation sites differs little from what it was some 80 mya, except by being somewhat warmer and perhaps a bit less arid then. This is testimony to the fact that the location has long been so far from any major source of evaporation that little rainfall reached it, even before the Himalayas were uplifted which bar clouds from reaching today's Gobi desert.

Most notable fossil discoveries have been the first confirmed dinosaur eggs (a clutch, probably of Oviraptor) and several dinosaur finds, Protoceratops, Pinacosaurus and Velociraptor being the most prominent.

The Flaming Cliffs, type locality of the Djadochta Formation

Flora and fauna

The fauna of the Djadochta Formation is very similar in composition to the nearby Bayan Mandahu Formation. The two share many of the same genera, but differ in the exact species. For example, the most common mammal in the Djadochta is Kryptobaatar dashzevegi, while in the Bayan Mandahu, it is the closely related Kryptobaatar mandahuensis. Similarly, the dinosaur fauna of the Djadochta includes Protoceratops andrewsi and Velociraptor mongoliensis, which the Bayan Mandahu yields Protoceratops hellenikorhinus and Velociraptor osmolskae.^[1] It is likely that the nearby Bayn Mandahu represents a slightly younger, perhaps by 1 million years, assemblage of slightly more derived animals, possibly the direct descendants of their Djadochta counterparts.^[2]

Amphibians

A frog of uncertain classification is known from the formation.

Crocodylomorphs

Crocodylomorphs of the Djadochta Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Gobiosuchus	G. kielanae				A gobisuchid.
Shamosuchus	S. djadochtaensis				A mesoeucrocodylian.
Zaraasuchus	Z. shepardi				A gobisuchid.
Zosuchus	Z. davidsoni				A basal crocodyliform.

Lizards

Lizards of the Djadochta Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Aiolosaurus	A. oriens					Estesia
Anchaurosaurus	A. gilmorei				A primitive iguanid.
Estesia	E. mongoliensis				An anguimorph.
Gobiderma	G. pulchra				An anguimorph.
Mimeosaurus	M. crassus				An agamid.
Pleurodontagama	P. aenigmatodes				An agamid.
Priscagama	P. gobiensis				An agamid.
Xihaina	X. aquilonia				A primitive iguanid.

Mammals

Mammals of the Djadochta Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Bulganbaatar	B. nemegtbaataroides				A marsupial.	Zalambdalestes
Deltatheridium	D. pretrituberculare				A marsupial.
Deltatheroides	D. cretacicus				A marsupial.
Hyotheridium	H. dobsoni				A therian mammal of uncertain classification.
Kamptobaatar	K. kuczynskii				A multituberculate.
Kennalestes	K. gobiensis				A placental. Also present in the Bayan Mandahu Formation.
Kryptobaatar	K. dashzevegi	Ukhaa Tolgod[3] Zos Wash[3]			A multituberculate, the most common mammal in this formation.[1]
Zalambdalestes	Z. lechei	Ukhaa Tolgod[3] Zos Wash[3]			A placental.

Ornithischians

A hadrosaur of uncertain classification is known from the formation.

Ornithischian dinosaurs of the Djadochta Formation
Genus	Species	Location	Abundance	Notes	Images
Pinacosaurus	P. grangeri	Bayan Dzak[2] Ukhaa Tolgod[2]		An ankylosaur.	Pinacosaurus Protoceratops
	P. mephistocephalus	Bayan Mandahu
	Indeterminate	Tugriken Shireh[2]		An ankylosaur.
Protoceratops	P. andrewsi	Bayan Dzak[2] Tugriken Shireh[2] Ukhaa Tolgod[3] Zos Wash[3]		A protoceratopsid.
	P. hellenikorhinus	Bayan Mandahu
	Indeterminate	Ukhaa Tolgod[2]		A protoceratopsid.

Saurischians

A sauropod of uncertain classification is known from the formation.

Color key Taxon Reclassified taxon Taxon falsely reported as present Discredited taxon Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative data are in small text; crossed out data are discredited.

Saurischian dinosaurs reported from the Djadochta Formation
Genus	Species	Location	Material	Notes	Images
Apsaravis[4]	A. ukhaana[4]	Ukhaa Tolgod[5]	"Partial postcranial skeleton."[6]	A basal ornithurine bird only known from this formation.	Byronosaurus hatchlings Citipati and nest Khaan Saurornithoides Velociraptor
Archaeornithoides[4]	A. deinosauriscus[4]	Bayn Dzak[7]	"Partial skull."[8]	A coelurosaur of uncertain relationships
Byronosaurus[4]	B. jaffei[4]	Ukhaa Tolgod[2]	"Skull and fragmentary postcranium, [and a] fragmentary skull."[9]	A troodontid
Citipati[4]	C. osmolskae[4]	Ukhaa Tolgod[2]	"Skeleton with skull, partial postcranium, embryo to adult."[10]	An oviraptorid found brooding its eggs
	Citipati sp.	Zamyn Khondt[2]		An oviraptorid with a distinctive, tall crest
Khaan	K. mckennai	Ukhaa Tolgod[2]	"[Three] skeletons with skulls."[10]	An oviraptorid
Kol	K. ghuva	Ukhaa Tolgod[11]		An alvarezsaurid
Mahakala	M. omnogovae	Tugriken Shireh[2]		A dromaeosaurid
Oviraptor[12]	O. philoceratops[12]	Bayan Dzak[2]	"[One] partial skeleton with skull"[13]	An oviraptorid.
?Parvicursor	Indeterminate	Tugriken Shireh[2]		An alvarezsaurid.
Quaesitosaurus	Q. orientalis		"Partial skull."[14]
Saurornithoides[12]	S. mongoliensis[12]	Bayan Dzak[2]	"Skull with fragmentary postcranial skeleton."[9]	A troodontid.
Shuvuuia[4]	S. deserti[4]	Ukhaa Tolgod[2] Zos Wash[3]	"Skull and postcranial skeleton."[15]	An alvarezsaurid
Tyrannosauridae indet.	Indeterminate[12]	Bayan Dzak[2] Bayan Mandahu[2][16]		A tyrannosaurid possible referable to Tarbosaurus.
Tsaagan	T. mangas	Ukhaa Tolgod[2]		A dromaeosaurid
Velociraptor[12]	V. mongoliensis[12]	Bayan Dzak[2] Tugriken Shireh[2]		A dromaeosaurid.
Unnamed dromaeosaurid	Unnamed	Zos Wash[3]
Unnamed troodontid	Unnamed, specimen IGM 100/1005	Zos Wash[3]

See also

• Barun Goyot Formation
• List of fossil sites (with link directory)
• Nemegt Formation
• List of dinosaur-bearing rock formations

Footnotes

1. ^ ^{a b} Godefroit, Pascal; Currie, Philip J.; Li Hong; Shang Chang Yong; and Dong Zhi-ming (2008). "A new species of Velociraptor (Dinosauria: Dromaeosauridae) from the Upper Cretaceous of northern China". Journal of Vertebrate Paleontology 28 (2): 432–438. doi:10.1671/0272-4634(2008)28[432:ANSOVD]2.0.CO;2. ISSN 0272-4634. 
2. ^ ^{a b c d e f g h i j k l m n o p q r s t u} Nicholas R. Longrich, Philip J. Currie, Dong Zhi-Ming (2010). "A new oviraptorid (Dinosauria: Theropoda) from the Upper Cretaceous of Bayan Mandahu, Inner Mongolia". Palaeontology 53 (5): 945–960. doi:10.1111/j.1475-4983.2010.00968.x. 
3. ^ ^{a b c d e f g h i} Norell, M.A.; Clark, J.M.; Turner, A.H.; Makovicky, P.J.; Barsbold, R.; Rowe, T. (2006). "A new dromaeosaurid theropod from Ukhaa Tolgod (Omnogov, Mongolia)". American Museum Novitates 3545: 1–51. doi:10.1206/0003-0082(2006)3545[1:ANDTFU]2.0.CO;2. ISSN 0003-0082. 
4. ^ ^{a b c d e f g h i j} "47.4 Ömnögov', Mongolia; 2. Djadochta Formation." Weishampel, et al. (2004). Pg. 596.
5. ^ Clarke, Julia A., Norell, Mark A. (2002). "The morphology and phylogenetic position of Apsaravis ukhaana from the Late Cretaceous of Mongolia". American Museum Novitates, No. 3387, American Museum of Natural History, New York, NY.
6. ^ "Table 11.1," in Weishampel, et al. (2004). Page 214.
7. ^ Spelled "Ömnögov'" in "47.4 Ömnögov', Mongolia; 2. Djadochta Formation." Weishampel, et al. (2004). Pg. 596.
8. ^ "Table 4.1," in Weishampel, et al. (2004). Page 76.
9. ^ ^{a b} "Table 9.1," in Weishampel, et al. (2004). Page 185.
10. ^ ^{a b} "Table 8.1," in Weishampel, et al. (2004). Page 167.
11. ^ Turner, A.H.; Nesbitt, S.J.; Norell, M.A. (2009). "A Large Alvarezsaurid from the Cretaceous of Mongolia". American Museum Novitates 3648: 1–14. 
12. ^ ^{a b c d e f g} "48.11 Nei Mongol Zizhiqu, People's Republic of China; 2. Djadochta Formation." Weishampel, et al. (2004). Pg. 598.
13. ^ "Table 8.1," in Weishampel, et al. (2004). Page 166.
14. ^ "Table 13.1," in Weishampel, et al. (2004). Page 263.
15. ^ "Table 11.1," in Weishampel, et al. (2004). Page 211.
16. ^ "Inner Mongolia" is referred to as "Nei Mongol Zizhiqu" in "48.11 Nei Mongol Zizhiqu, People's Republic of China; 2. Djadochta Formation." Weishampel, et al. (2004). Pg. 598.

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.