Djadochta Formation

Djadochta Formation Stratigraphic range: Campanian, 75–71 Ma PreЄ Є O S D C P T J K Pg N ↓
Type	Geological formation
Lithology
Primary	Sandstone
Location
Region	Asia
Country	Mongolia

The Djadochta Formation (sometimes transcribed Djadokhta) is a geological formation situated in central Asia (Gobi Desert), dating from the Late Cretaceous Period. Laid down in the early Campanian, possibly starting in the latest Santonian, it is dated somewhat uncertainly at about 75-71 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.

File:Resized pan-flaming-cropped2.jpg

The Flaming Cliffs, type locality of the Djadochta Formation.

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. 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.

Amphibians

A frog of uncertain classification is known from the formation.

Crocodylomorphs

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

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

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

Ornithischians

Genus	Species	Location	Abundance	Notes	Images
Pinacosaurus	P. grangeri	Bayan Dzak Ukhaa Tolgod Alag Teg Tugriken Shireh		An ankylosaur.	File:Pinacosaurus resting.JPG Pinacosaurus Protoceratops
	P. mephistocephalus	Bayan Mandahu
	Indeterminate	Tugriken Shireh		An ankylosaur.
Plesiohadros	P. djadokhtaensis	Alag Teg		A basal hadrosaurid.
Protoceratops	P. andrewsi	Bayan Dzak Tugriken Shireh Ukhaa Tolgod Zos Wash		A protoceratopsid.
	P. hellenikorhinus	Bayan Mandahu
	Indeterminate	Ukhaa Tolgod		A protoceratopsid.

Saurischians

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.

Saurischian dinosaurs reported from the Djadochta Formation
Genus	Species	Location	Material	Notes	Images
Apsaravis	A. ukhaana	Ukhaa Tolgod	"Partial postcranial skeleton."	A basal ornithurine bird only known from this formation.	File:Juvenile Deinonychosaur.jpg Byronosaurus hatchlings Citipati and nest File:Khaan.jpg Khaan File:Saurornithoides mongoliensis.jpg Saurornithoides Velociraptor
Archaeornithoides	A. deinosauriscus	Bayn Dzak	"Partial skull."	A coelurosaur of uncertain relationships
Byronosaurus	B. jaffei	Ukhaa Tolgod	"Skull and fragmentary postcranium, [and a] fragmentary skull."	A troodontid
Citipati	C. osmolskae	Ukhaa Tolgod	"Skeleton with skull, partial postcranium, embryo to adult."	An oviraptorid found brooding its eggs
	Citipati sp.	Zamyn Khondt		An oviraptorid with a distinctive, tall crest
Gobipteryx	G. minuta	Ukhaa Tolgod		An enantiornithine also known from the Barun Goyot Formation
Gobivenator	G. mongoliensis		"Almost complete skeleton."	A troodontid theropod.
Khaan	K. mckennai	Ukhaa Tolgod	"[Three] skeletons with skulls."	An oviraptorid.
Kol	K. ghuva	Ukhaa Tolgod	"A well-preserved right foot"	An alvarezsaurid.
Mahakala	M. omnogovae	Tugriken Shireh		A dromaeosaurid.
Oviraptor	O. philoceratops	Bayan Dzak	"[One] partial skeleton with skull"	An oviraptorid.
?Parvicursor	Indeterminate	Tugriken Shireh		An alvarezsaurid.
Saurornithoides	S. mongoliensis	Bayan Dzak	"Skull with fragmentary postcranial skeleton."	A troodontid.
Shuvuuia	S. deserti	Ukhaa Tolgod Zos Wash	"Skull and postcranial skeleton."	An alvarezsaurid
cf. Tarbosaurus	Indeterminate			A tyrannosaurid, may actually be Zhuchengtyrannus.
Tyrannosauridae indet.	Indeterminate	Bayan Dzak Bayan Mandahu		A tyrannosaurid possible referable to Alectrosaurus.
Tsaagan	T. mangas	Ukhaa Tolgod		A dromaeosaurid.
Velociraptor	V. mongoliensis	Bayan Dzak Tugriken Shireh Ukhaa Tolgod		A dromaeosaurid.
cf. Zhuchengtyrannus	Indeterminate			A tyrannosaurid, may actually be Tarbosaurus.
Unnamed dromaeosaurid	Unnamed	Zos wash
Unnamed troodontid	Unnamed, specimen IGM 100/1005	Ukhaa Tolgod
Ornithomimosauria indet.	Unnamed, specimen IGM 100/1245 and IGM 100/987	Uhkaa Tolgod	skull fragments

Eggs

Oogenus	Oospecies	Location	Material	Notes
Styloolithus	S. sabathi	Bayn Dzak		Probably avian
Protoceratopsidovum	P. sincerum P. minimum P. fluxuosum
Elongatoolithus	E. frustrabilis E. Subtitectorius
Spheroolithus	S. maiasauroides S. tenuicorticus
Macroolithus	M. mutabilis
Subtiliolithus	spp.

See also

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

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.