Djadochta Formation | |
---|---|
Stratigraphic range: Campanian, ~ | |
Type | Geological formation |
Unit of | Shamo Group |
Sub-units | Bayn Dzak Member, Tugrugyin Member |
Underlies | Barun Goyot Formation |
Overlies | Alagteeg Formation |
Area | Nemegt Basin, Ulan Nur Basin |
Thickness | over 90 m (300 ft) |
Lithology | |
Primary | Sandstone |
Other | Mudstone |
Type section | |
Named for | Shabarakh Usu (Bayn Dzak) |
Named by | Berkey & Morris |
Location | Flaming Cliffs |
Year defined | 1927 |
Coordinates | 44°08′19″N103°43′40″E / 44.13861°N 103.72778°E |
Approximate paleocoordinates | 30°42′N9°12′E / 30.7°N 9.2°E |
Region | Ömnögov |
Country | Mongolia |
Thickness at type section | about 90 m (300 ft) |
The Djadochta Formation (sometimes transcribed and also known as Djadokhta, Djadokata, or Dzhadokhtskaya) is a highly fossiliferous geological formation situated in Central Asia, Gobi Desert, dating from the Late Cretaceous period, about 75 million to 71 million years ago. The type locality is the Bayn Dzak locality, famously known as the Flaming Cliffs. Reptile (including dinosaur) and mammal remains are among the fossils recovered from the formation.
The Djadochta Formation was first documented and explored—though only a single locality—during paleontological expeditions of the American Museum of Natural History in 1922–1925, which were part of the Central Asiatic Expeditions. The expeditions were led by Roy Chapman Andrews, in company of Walter Willis Granger as chief paleontologist and field team. The team did extensive exploration at the Bayn Dzak (formerly Shabarakh Usu) region, which they nicknamed Flaming Cliffs given that at sunset the sediments of this locality had a characteristic reddish color. Notable finds included the first known fossils of Oviraptor , Protoceratops , Saurornithoides , and Velociraptor , the first confirmed dinosaur eggs (a partial nest of Oviraptor), as well as fossil mammals. Some of these were briefly described by Henry Fairfield Osborn during the ongoing years of the expeditions. In 1927 the formation was formally described and established by Berkey and Morris, with Bayn Dzak as the type locality. [1] [2]
In 1963, the Mongolian paleontologist Demberelyin Dashzeveg reported the discovery of a new fossiliferous locality of the Djadochta Formation: Tugriken Shireh. [3] During the 1960s to 1970s, Polish-Mongolian and Russian-Mongolian paleontological expeditions collected new, partial to complete specimens of Protoceratops and Velociraptor at this locality, making these dinosaur species a common occurrence in Tugriken Shireh. [4] Some of the most notable excavations made at Tugriken Shireh include the Fighting Dinosaurs (Protoceratops and Velociraptor locked in combat), [5] [6] and abundant articulated, in situ (in the original pose), and sometimes complete skeletons of Protoceratops. [7] [8]
During the 1980s, a joint Soviet-Mongolian paleontological expedition discovered several Mesozoic fossil-rich localities in the Gobi Desert of Mongolia. Among these sites, Udyn Sayr was discovered and examined by the expedition, regarding its age as Late Cretaceous. This new locality was predominantly rich in avimimid fossils, with a lesser abundance of mammal and other dinosaur fossils. [4]
In 1993 teams of a collaborative Mongolian-North American expedition (supported by the Mongolian Academy of Sciences and American Museum of Natural History) discovered a new fossil locality of the Djadochta Formation called Ukhaa Tolgod (meaning "Brown Hills"). Like previous localities, Ukhaa Tolgod has yielded a prominent abundance of well-preserved fossils, including high concentrations of mammal, dinosaur, lizard, and egg remains. A vast majority of specimens from this locality are usually found in near-complete articulation. Overall, when compared to other Mesozoic fossil sites, the diversity of fossils in Ukhaa Tolgod is unusually high. [9] [10]
The modern-day Djadochta Formation is set in an arid habitat of sand dunes with little freshwater apart from oases and arroyos, in the Gobi Desert. The dominant lithology of the Djadochta Formation is represented by non-marine, cemented reddish-orange and pale orange to light gray, medium to fine-grained sands and sandstones, which include minor deposits of calcareous concretions and orange-brown silty clay. Less abundant sedimentation comprises conglomerates, siltstones, fluvial (water-deposited) sandstones, and mudstones. The entire thickness of the formation in the Ulan Nur Basin is at least 80 m (260 ft). Several aeolian processes (wind works) indicate the presence of large straight-crested dune-like structures, and smaller barchan (crescent-shaped) and parabolic (poorly U-shaped) dunes across the formation. [11] [12] [10] Reddish sandstones are observed in numerous localities. [12] [10]
The Djadochta Formation occurs in the Late Cretaceous period of the Campanian stage. Magnetostratigraphic datings from the Bayn Dzak and Tugriken Shireh localities suggest that the Djadochta Formation was deposited during a time of rapidly changing polarity at about 75 million to 71 million years ago. [12]
The Djadochta Formation is separated into a lower Bayn Dzak Member and an upper Turgrugyin Member, which represent very similar depositional environments. [12] Further strata from the Bayn Dzak Member includes that of the Ukhaa Tolgod locality, and its overall age is regarded also within the Campanian. [10]
Based on the superposition of the members, the Tugrugyin Member overlies the Bayn Dzak Member making it somewhat younger, which indicates that the Bayn Dzak paleofauna lived somewhat earlier than that from Tugriken Shireh. However, it is not yet understood the precise temporal difference: [12] Localities within the Djadochta Formation are considered to represent a sequence of progressively younger sediments and thereby paleofaunas. Ukhaa Tolgod may be younger than both Bayn Dzak and Tugriken Shireh. [18] Based on their fossil record and strata, Udyn Sayr and Zamyn Khondt have been correlated with other Djadokhta localities, though fossils of Udyn Sayr may indicate that this locality is younger than Bayn Dzak and Tugriken Shireh. [19]
Examinations on the strata of the Alag Teg (also spelled Alag Teeg or Alag Teer) locality, once considered part of this formation, indicates that it belongs to a different geological formation: the Alagteeg Formation, which is slightly older than the overlying Djadochta Formation. Based on sediments and stratigraphic relationships, the lower part of the Bayn Dzak locality is correlated with the Alag Teg locality, making both sections part of the Alagteeg Formation. The upper or main part of the former locality is considered part of the Djadochta Formation itself, as it shares similar lithology and stratigraphic relationships with Tugriken Shireh. [14]
Formation | Time period | Member | Lithology | Thickness | Image |
---|---|---|---|---|---|
Barun Goyot | Early Maastrichtian | Poorly cemented, fine and medium-grained red to reddish-brown sandstones. | ~110 m (360 ft) | ||
Djadochta | Campanian | ||||
Turgrugyin | Pale orange to light gray (sometimes yellowish-white) sands and sandstones. | 30 m (98 ft) | |||
Bayn Dzak | Reddish-orange, crossbedded, and structureless sandstones, with minor deposits of brown siltstones and mudstones. | 90 m (300 ft) | |||
Alagteeg | Early Campanian Santonian | "lower Bayn Dzak" | Alternating reddish brown mudstone and horizontally laminated sandstone, with ripple cross laminations and rhizoliths. | ~15 m (49 ft) | |
Based on strata and rock facies (such as sandstones and caliche) of the formation and coeval units (Bayan Mandahu) it is currently agreed that sediments of the Djadochta Formation were deposited by wind activity in arid paleoenvironments comprising sand dunes with a warm semi-arid climate. [20] [12] [14] Fluvial sedimentation at the Ukhaa Tolgod locality indicates the presence of short-lived water bodies during the times of the formation, which also contributed to its deposition. [10]
A vast majority of articulated specimens from the Djadochta Formation are found in unstructured sandstones, indicating burial in situ by high-energy sand-bearing events. Some buried Protoceratops individuals are preserved in distinctive postures involving the body and head arched upwards, suggesting that the animals died in the process of trying to free themselves from the body of sand, where they eventually fossilized. As they were unable to escape burial, the sandy mass prevented carcasses from being scavenged by vertebrates. Most of these "buried" specimens are found with bite traces and large borings (tunnel-like holes made by small invertebrates) on bone joints areas and other surfaces, indicating that after death they were largely scavenged by invertebrates, such as skin beetles. [21] [22] [23]
It has been suggested that the repeated occurrence of these feeding traces at limb joints may reflect that the responsible scavengers focused on collagen at the joint cartilage of dried dinosaur carcasses as a source of nitrogen, which was very low in the arid Djadochta Formation environments. [24]
Examinations at the fossil preservation and sediments of Ukhaa Tolgod indicates that preserved animals were buried alive by catastrophic dune collapses. It is thought to have occurred when sand dunes became oversaturated with water resulting in their sudden downfall; heavy rainfall events likely acted as the triggering mechanism for this collapse. [9] [25] [10] Examples from the Ukhaa Tolgod preservation include Citipati (brooding adults entombed atop nests and eggs); [26] [27] Khaan (a pair in close proximity likely killed by a single collapse event); [28] and Saichangurvel (individual buried alive by a muddy dune). [29]
Among fossils, Protoceratops is extremely common in Djadochta localities. Bayn Dzak is reported as one of the localities with the highest concentration of Protoceratops fossils and has been noted as the "Protoceratops fauna". [30] Adjacent to Bayn Dzak, at Tugriken Shireh, Protoceratops is also abundant. [15] Other common dinosaur components of the paleofauna include Pinacosaurus and Velociraptor . [11] Small vertebrates like lizards and mammals are rather abundant and diverse, with Adamisaurus and Kryptobaatar being the most abundant representatives. [29] [31] [30] The paleofauna of the Djadochta Formation is very similar in composition to the nearby and coeval-regarded Bayan Mandahu Formation of Inner Mongolia. The two formations share many of the same genera, but differ in species. For instance, the most common mammal in Djadochta is Kryptobaatar dashzevegi, while in Bayan Mandahu it is the closely related K. mandahuensis. Similarly, the dinosaur fauna of Djadochta includes Protoceratops andrewsi and Velociraptor mongoliensis, which Bayan Mandahu yields P. hellenikorhinus and V. osmolskae. [20] [32]
Although fossil plants are extremely rare in the Djadochta Formation, the great abundancy of herbivorous Protoceratops at the arid-deposited Tugriken Shireh locality indicates that it had a moderate coverage of bushes or other low-growing plants. [15]
The relatively low paleobiodiversity and climate settings of the Djadochta suggest that these conditions contributed to stressed paleoenvironments. Most of the fossil occurrences in the formation are occupied by Protoceratops, and small to medium-sized ankylosaurs, oviraptorids, and dromaeosaurids make much of the overall paleofauna. Large-bodied animals are absent or extremely rare in the formation. Comparisons with the Nemegt Formation further reflects stressed paleoenvironments. In contrast to Djadochta, Nemegt has yielded an extensive diversity of large dinosaur taxa, such as Deinocheirus , Nemegtosaurus , Saurolophus , Tarbosaurus , or Therizinosaurus . Most of these taxa are herbivorous, which combined with the mesic (well-watered) settings of the Nemegt Formation allowed the development of giant herbivores, in contrast to the stressed Djadochta Formation. Another indicative of stressed paleoenvironments is the almost non-existent amount of fully aquatic animals. Turtles are rarely recovered, and most are terrestrial such as Zangerlia . [30]
Tyrannosaurids found in the formation may belong to an indeterminate species of Tarbosaurus , possibly extending the time range of the genus. [33] It is suggested that most of the fragmented hadrosaur, tyrannosaur and sauropod remains across the formation likely belong to non-endemic, passing by species. [30]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Radicites | R. gobiensis | Bayn Dzak | "Twenty plant roots." [34] | A tracheophyte, likely conifer. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Gobiates | Indeterminate | Udyn Sayr | "Partial skeleton with partial urostyle." [35] | A frog. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Artzosuchus | A. brachicephalus | Udyn Sayr | "Partial skull." [36] | A crocodylomorph. | |
Gobiosuchus | G. kielanae | Bayn Dzak | "Multiple specimens with partial skulls and skeletons." [37] [38] | A gobisuchid. | |
G.? parvus | Udyn Sayr | "Partial skull and skeleton." [39] [40] | A gobisuchid. | ||
Shamosuchus | S. djadochtaensis | Bayn Dzak, Ukhaa Tolgod | "Two skulls and partial skeleton." [41] [42] | A paralligatorid. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Adamisaurus | A. magnidentatus | Bayn Dzak, Tugriken Shireh, Ukhaa Tolgod | "Skulls and skeletons from multiple specimens." [43] [29] | A teiid. Also present in the Barun Goyot Formation and Bayan Mandahu Formation. | |
Aiolosaurus | A. oriens | Ukhaa Tolgod | "Incomplete skull and partial skeleton." [29] | A varanoid. | |
Carusia | C. intermedia | Bayn Dzak, Ukhaa Tolgod | "Skulls from multiple specimens." [29] | A carusiid. Also present in the Barun Goyot Formation and Bayan Mandahu Formation. | |
Cherminotus | C. longifrons | Tugriken Shireh, Ukhaa Tolgod | "Skulls and partial skeleton." [29] | A varanoid. Also present in the Barun Goyot Formation. | |
Ctenomastax | C. parva | Zos | "Incomplete skull." [29] | An iguanid. Also present in the Barun Goyot Formation. | |
Dzhadochtosaurus | D. giganteus | Tugriken Shireh | "Partially complete skull." [44] | A macrocephalosaur. | |
Eoxanta | E. lacertifrons | Ukhaa Tolgod | "Incomplete skull." [29] | A scincomorph. Also present in the Barun Goyot Formation. | |
Estesia | E. mongoliensis | Bayn Dzak, Ukhaa Tolgod | "Partial skulls and teeth." [29] | A monstersaur. Also present in the Barun Goyot Formation. | |
Flaviagama | F. dzerzhinskii | Tugriken Shireh | "Skull and two vertebrae." [45] | A priscagamid. | |
Globaura | G. venusta | Bayn Dzak, Ukhaa Tolgod | "Partial skulls." [29] | A scincomorph. Also present in the Barun Goyot Formation. | |
Gobiderma | G. pulchrum | Udyn Sayr, Ukhaa Tolgod | "Skulls and skin impressions." [29] | A monstersaur. Also present in the Barun Goyot Formation. | |
Gobinatus | G. arenosus | Ukhaa Tolgod | "Partial skull." [29] | A teiid. Also present in the Barun Goyot Formation. | |
Hymenosaurus | H. clarki | Ukhaa Tolgod | "Partial skull." [29] | A scincomorph. | |
Isodontosaurus | I. gracilis | Bayn Dzak, Tugriken Shireh, Ukhaa Tolgod, Zos | "Numerous skulls and a partial skeleton." [29] | An iguanian. Also present in the Bayan Mandahu Formation. | |
Macrocephalosaurus | Indeterminate | Ukhaa Tolgod | "Partial skull and skeleton." [29] | A teiid. Also present in the Barun Goyot Formation. | |
Mimeosaurus | M. crassus | Bayn Dzak, Ukhaa Tolgod, Zos Wash | "Partially complete skulls." [29] | An acrodont. Also present in the Bayan Mandahu Formation. | |
Myrmecodaptria | M. microphagosa | Ukhaa Tolgod | "Single skull." [29] | A gekkotan. | |
Ovoo | O. gurval | Little Ukhaa Tolgod | "Partial skull." [46] | A varanid. | |
Parmeosaurus | P. scutatus | Ukhaa Tolgod | "Articulated skull and skeleton." [29] | A scincomorph. | |
Phrynosomimus | P. asper | Ukhaa Tolgod | "Two partial skulls." [29] | An acrodont. Also present in the Barun Goyot Formation. | |
Priscagama | P. gobiensis | Bayn Dzak, Ukhaa Tolgod | "Incomplete skulls." [29] | An priscagamid. Also present in the Barun Goyot Formation. | |
Saichangurvel | S. davidsoni | Ukhaa Tolgod | "Complete skull and skeleton in articulation." [47] | An iguanian. | |
Slavoia | S. darevskii | Ukhaa Tolgod | "Skulls and skeleton." [29] | A scincomorph. Also present in the Barun Goyot Formation. | |
Telmasaurus | T. grangeri | Bayn Dzak | "Partial skull and skeleton." [48] [29] | A varanid. | |
Temujinia | T. ellisoni | Tugriken Shireh, Ukhaa Tolgod | "Several partial skulls." [29] | An iguanid. | |
Tchingisaurus | T. multivagus | Ukhaa Tolgod | "Partial skull." [29] | A teiid. | |
Unnamed scincomorph | Indeterminate | Ukhaa Tolgod | "Partial skull." [29] | A scincomorph. | |
Varanoidea indet. | Indeterminate | Ukhaa Tolgod | "Partial maxilla and vertebra." [29] | A varanoid. | |
Zapsosaurus | Z. sceliphros | Tugriken Shireh | "Two partial skulls." [29] | An iguanid. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Asiatherium | A. reshetovi | Udyn Sayr | "Articulated skull and skeleton." [49] | A metatherian. | |
Bulganbaatar | B. nemegtbaataroides | Bayn Dzak, Ukhaa Tolgod | "Partial skull, and other remains." [50] [9] | A multituberculate. | |
Catopsbaatar | C. catopsaloides | Ukhaa Tolgod | Not specified. [9] | A djadochtatheriid. Also present in the Barun Goyot Formation. | |
Chulsanbaatar | C. vulgaris | Ukhaa Tolgod | "Skull and partial skeleton." [9] | A multituberculate. Also present in the Barun Goyot Formation. | |
Deltatheridium | D. pretrituberculare | Bayn Dzak, Ukhaa Tolgod | "Partial skull and skeleton remains." [51] [52] | A tribosphenid. | |
Deltatheroides | D. cretacicus | Bayn Dzak | "Partial skull." [51] | A djadochtatheriid. | |
Djadochtatherium | D. matthewi | Bayn Dzak, Tugriken Shireh | "Partial skulls." [53] [54] | A djadochtatheriid. | |
Hyotheridium | H. dobsoni | Bayn Dzak | "Partial skull." [51] | A therian. | |
Indeterminate | Ukhaa Tolgod | Not specified. [9] | A therian. | ||
Kamptobaatar | K. kuczynskii | Bayn Dzak, Ukhaa Tolgod | "Partial skull, and other remains." [55] [9] | A multituberculate. | |
Kennalestes | K. gobiensis | Bayn Dzak, Ukhaa Tolgod | "Nearly complete skull, and other remains." [56] [9] | An eutherian. | |
Kryptobaatar | K. dashzevegi | Bayn Dzak, Tugriken Shireh, Ukhaa Tolgod | "Skulls and skeleton remains from several specimens." [55] [31] | A djadochtatheriid. Gobibaatar and Tugrigbaatar are considered synonyms of this taxon. [57] | |
Maelestes | M. gobiensis | Ukhaa Tolgod | "Partial skull with skeleton." [58] | A cimolestid. | |
Mangasbaatar | M. udanii | Udyn Sayr | "Skulls and partial skeleton from two specimens." [59] | A djadochtatheriid. | |
Nemegtbaatar | N. gobiensis | Ukhaa Tolgod | Not specified. [9] | A multituberculate. Also present in the Barun Goyot Formation. | |
Sloanbaatar | S. mirabilis | Bayn Dzak, Ukhaa Tolgod | "Complete skull, and other remains." [55] [9] | A multituberculate. | |
Tombaatar | T. sabuli | Ukhaa Tolgod | "Partial skull." [60] | A djadochtatheriid. | |
Ukhaatherium | U. nessovi | Ukhaa Tolgod | "Partial to nearly complete skeletons from several specimens." [61] [62] [63] | An eutherian. | |
Zalambdalestes | Z. lechei | Bayn Dzak, Tugriken Shireh | "Skulls and skeletons from several specimens." [51] [64] | An eutherian. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Azhdarchidae indet. | Indeterminate | Tugriken Shireh | "Indeterminate bone inside the gut cavity of a Velociraptor." [65] | An azhdarchid. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Nanhsiungchelyidae indet. | Indeterminate | Abdrant Nuru | "Three shell fragments." [66] | A nanhsiungchelyid. | |
Indeterminate | Bayn Dzak | "Partial shells." [66] | A nanhsiungchelyid. | ||
Indeterminate | Udyn Sayr | "Two shell fragments." [66] | A nanhsiungchelyid. | ||
Zangerlia | Z. dzamynchondi | Zamyn Khondt | "Partial shell." [67] | A nanhsiungchelyid. | |
Z. ukhaachelys | Ukhaa Tolgod | "Partial skull and skeleton." [68] | A nanhsiungchelyid. | ||
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Minotaurasaurus | M. ramachandrani | Ukhaa Tolgod | [Two] complete skulls, mandibles, and first cervical half-ring. [69] [70] | An ankylosaurid previously thought to be a junior synonym of Tarchia, but is now considered to be a valid and distinct taxon. | |
Pinacosaurus | P. grangeri | Bayn Dzak, Ukhaa Tolgod | [Three] skulls, mandibles, predentary, cervical vertebrae, dorsal vertebrae, caudal vertebrae, ribs, scapula, coracoids, humerus, radius, ulna, ilium, femora, tibia, fibula, pelvis, manus, tail club handles, cervical half-rings, osteoderms, and a nearly complete skeleton lacking a skull. [71] [72] [73] | An ankylosaurid also known from the Alagteeg Formation and Bayan Mandahu Formation. | |
Ankylosauridae indet. | Indeterminate | Zamyn Khondt | Partially complete postcranial skeleton with in situ osteoderms. [74] | Previously referred to Saichania, but is now referred to as Ankylosauridae indet., or cf. Pinacosaurus . [74] |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Bainoceratops | B. efremovi | Bayn Dzak | "Partial vertebrae." [75] | A protoceratopsid. May be synonymous with Protoceratops. [76] | |
Bagaceratops | Indeterminate | Udyn Sayr | "Skull with partial skeleton." [19] | A protoceratopsid. Indeterminate between Bagaceratops and Protoceratops. [19] | |
Protoceratops | P. andrewsi | Bayn Dzak, Tugriken Shireh, Udyn Sayr, Zamyn Khondt | "Multiple partial to complete specimens." [77] [7] [78] [8] [19] | A protoceratopsid. | |
P. hellenikorhinus | Bor Tolgoi, Udyn Sayr | "Partial cranial remains." [79] | A protoceratopsid. | ||
Protoceratopsidae indet. | Indeterminate | Ukhaa Tolgod | "Numerous skulls and remains." [80] [81] | A protoceratopsid. | |
Udanoceratops | U. tschizhovi | Udyn Sayr | "Skull and fragmented skeleton elements." [82] | A giant leptoceratopsid. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Hadrosauroidea indet. | Indeterminate | Tugriken Shireh | "Fragmented remains from juveniles." [83] [84] | A hadrosauroid. | |
Plesiohadros | P. djadokhtaensis | Alag Teeg | "Skull and partial body elements." [84] | A hadrosauroid. Actually hails from the Alagteeg Formation. [85] | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Goyocephale | G. lattimorei | Boro Khovil | "Partial skull and skeleton." [86] | A pachycephalosaurid. Locality sediments may belong to this formation. [86] [87] | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Sauropoda indet. | Indeterminate | Not specified. [88] | Not specified. [88] | A sauropod. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Alvarezsauridae indet. | Indeterminate | Tugriken Shireh | "Partial skull, braincase, and skeleton elements of two specimens." [89] [90] | An alvarezsaurid also known as the Tugriken Shireh alvarezsaur. Uncertainly referred as Parvicursor sp. [90] | |
Kol | K. ghuva | Ukhaa Tolgod | "A well-preserved right foot." [91] | A large alvarezsaurid. Its classification has been criticized. [92] | |
Shuvuuia | S. deserti | Ukhaa Tolgod | "Multiple specimens with skull and skeletons." [93] [94] [95] [96] [97] | An alvarezsaurid. | |
Undescribed Alvarezsauridae | Indeterminate | Bayn Dzak | "Partial pelvic girdle and hindlimb." [98] | An alvarezsaurid. | |
Indeterminate | Gilvent Wash | Not given. [96] | An alvarezsaurid. | ||
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Apsaravis | A. ukhaana | Ukhaa Tolgod | "Partial postcranial skeleton." [99] | A basal ornithurine bird. | |
Elsornis | E. keni | Tugriken Shireh | "Partial articulated skeleton lacking the skull." [100] | An enantiornithe. | |
Gobipteryx | G. minuta | Ukhaa Tolgod | "Partial skull." [101] | An enantiornithine. Also present in the Barun Goyot Formation. | |
Protoceratopsidovum' | P. fluxuosum | Bayn Dzak | "Partial eggs." [102] | Eggs probably laid by a bird. [103] | |
P. minimum | Baga Tariach, Tugriken Shireh | "Clutch of four eggs and one pole of egg." [102] | Eggs probably laid by a bird. [103] | ||
P. sincerum | Bayn Dzak, Tugriken Shireh | "Multiple eggs and shells." [102] | Eggs probably laid by a bird. [103] | ||
Styloolithus | S. sabathi | Bayn Dzak | "Partial to complete eggs." [103] | Eggs probably laid by a bird. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Tsaagan | T. mangas | Ukhaa Tolgod | "Skull and partial skeleton." [104] | A dromaeosaurid | |
Velociraptor | V. mongoliensis | Bayn Dzak, Chimney Buttes, Gilvent Wash, Tugriken Shireh, Udyn Sayr, Ukhaa Tolgod | "Multiple partial to complete specimens." [105] [106] [107] [108] [109] [110] | A dromaeosaurid. | |
Undescribed Dromaeosauridae | Indeterminate | Abdrant Nuru | "Claw." [111] | A dromaeosaurid. | |
Indeterminate | Zos Wash | "Frontal region." [104] | A dromaeosaurid. Differs from Tsaagan . [104] | ||
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Halszkaraptor | H. escuilliei | Ukhaa Tolgod | "Partial skeleton with complete skull." [112] | A halszkaraptorine. | |
Mahakala | M. omnogovae | Tugriken Shireh | "Fragmented skull and skeleton." [113] | A halszkaraptorine. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Aepyornithomimus | A. tugrikinensis | Tugriken Shireh | "Nearly complete foot." [114] | An ornithomimid. | |
Ornithomimosauria indet. | Indeterminate | Ukhaa Tolgod | "Partial braincase, jaw tips, ribs, and vertebral fragments". [115] [116] | An ornithomimid. | |
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Avimimus | A. portentonsus | Udyn Sayr | "Partial skull and skeleton." [117] [118] | An avimimid. Its locality origin has been disputed and may hail from the Nemegt Formation. [119] | |
Citipati | C. osmolskae | Ukhaa Tolgod | "Multiple specimens with partial to nearly complete skeletons, an embryo, eggs and nesting individuals." [120] [121] [122] [27] | An oviraptorid. | |
Elongatoolithus | E. frustrabilis | ||||
E. subtitectorius | |||||
Khaan | K. mckennai | Ukhaa Tolgod | "Several specimens with partial to complete skeletons and skulls." [121] [123] [28] | An oviraptorid. | |
Macroolithus | M. mutabilis | "Eggs." | Eggs probably laid by an oviraptorid | ||
Oviraptor | O. philoceratops | Bayn Dzak | "Partial skeleton with skull, associated with a nest and juvenile." [124] [122] [27] | An oviraptorid. | |
Oviraptoridae indet. | Indeterminate | Zamyn Khondt | "Nearly complete skeleton with skull." [125] | An oviraptorid also known as the Zamyn Khondt oviraptorid. Uncertainly referred to Citipati . [121] [122] | |
Indeterminate | Zamyn Khondt | "Nearly complete skull with atlas and axis." [126] | An oviraptorid. | ||
Indeterminate | Udyn Sayr | "Assemblage of individuals." [27] | An oviraptorid. | ||
Indeterminate | Not specified. | "Two skulls with characteristic high crest." [127] [128] [129] | An oviraptorid. | ||
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Almas | A. ukhaa | Ukhaa Tolgod | "Skull with partial skeleton." [130] | A troodontid. | |
Archaeornithoides | A. deinosauriscus | Bayn Dzak | "Partial skull." [131] | A troodontid? Uncertain relationships among coelurosaurs. [131] [132] | |
Byronosaurus | B. jaffei | Ukhaa Tolgod | "Skull and fragmentary skeleton." [133] | A troodontid. | |
Gobivenator | G. mongoliensis | Zamyn Khondt | "Almost complete skeleton." [134] | A troodontid. | |
Saurornithoides | S. mongoliensis | Bayn Dzak | "Skull with fragmentary skeleton." [135] | A troodontid. | |
Troodontidae indet. | Indeterminate | Ukhaa Tolgod | "Partial skeleton." [136] | A troodontid. | |
Indeterminate | Ukhaa Tolgod | "Juvenile skulls, skeleton, and one nest." [137] [132] | A troodontid. Referred to either Almas, [138] [130] or Byronosaurus. [132] | ||
Indeterminate | Ukhaa Tolgod | "Fragmented skull and skeleton remains." [139] | A troodontid. Provisionally referred to Saurornithoides, [139] but now excluded. [135] | ||
Indeterminate | Ukhaa Tolgod | "Partial skull and skeletons from two specimens." [94] | A troodontid. | ||
Genus | Species | Location | Material | Notes | Images |
---|---|---|---|---|---|
Tyrannosauridae indet. | Indeterminate | Bayn Dzak | Not specified. [32] | A tyrannosaurid. | |
Indeterminate | Khongil | "Supraorbital, vertebra, rib, femur and metatarsals." [140] | A tyrannosaurid. | ||
Indeterminate | Not specified. | "Partial right ilium." [141] | A tyrannosaurid. | ||
Indeterminate | Not specified. | "Teeth." [20] | A tyrannosaurid. | ||
Velociraptor is a genus of small dromaeosaurid dinosaurs that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis, named and described in 1924. Fossils of this species have been discovered in the Djadochta Formation, Mongolia. A second species, V. osmolskae, was named in 2008 for skull material from the Bayan Mandahu Formation, China.
Oviraptor is a genus of oviraptorid dinosaur that lived in Asia during the Late Cretaceous period. The first remains were collected from the Djadokhta Formation of Mongolia in 1923 during a paleontological expedition led by Roy Chapman Andrews, and in the following year the genus and type species Oviraptor philoceratops were named by Henry Fairfield Osborn. The genus name refers to the initial thought of egg-stealing habits, and the specific name was intended to reinforce this view indicating a preference over ceratopsian eggs. Despite the fact that numerous specimens have been referred to the genus, Oviraptor is only known from a single partial skeleton regarded as the holotype, as well as a nest of about fifteen eggs and several small fragments from a juvenile.
Protoceratops is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus Protoceratops includes two species: P. andrewsi and the larger P. hellenikorhinus. The former was described in 1923 with fossils from the Mongolian Djadokhta Formation, and the latter in 2001 with fossils from the Chinese Bayan Mandahu Formation. Protoceratops was initially believed to be an ancestor of ankylosaurians and larger ceratopsians, such as Triceratops and relatives, until the discoveries of other protoceratopsids. Populations of P. andrewsi may have evolved into Bagaceratops through anagenesis.
Enigmosaurus is a genus of therizinosauroid that lived in Asia during the Late Cretaceous period. It was a medium-sized, ground-dwelling, bipedal herbivore that represents the third therizinosaur taxon from the Bayan Shireh Formation, although it is known from the lower part. The genus is monotypic, including only the type species E. mongoliensis, known from a well preserved pelvis and other tentative body remains.
Bagaceratops is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 72 to 71 million years ago. Bagaceratops remains have been reported from the Barun Goyot Formation and Bayan Mandahu Formation. One specimen may argue the possible presence of Bagaceratops in the Djadochta Formation.
The Bayan Shireh Formation is a geological formation in Mongolia, that dates to the Cretaceous period. It was first described and established by Vasiliev et al. 1959.
Bainoceratops is a genus of ceratopsian dinosaur from the late Campanian in the Late Cretaceous. The type species is B. efremovi. Its fossils were found in southern Mongolia in the Djadochta Formation.
Citipati is a genus of oviraptorid dinosaur that lived in Asia during the Late Cretaceous period, about 75 million to 71 million years ago. It is mainly known from the Ukhaa Tolgod locality at the Djadochta Formation, where the first remains were collected during the 1990s. The genus and type species Citipati osmolskae were named and described in 2001. A second species from the adjacent Zamyn Khondt locality may also exist. Citipati is one of the best-known oviraptorids thanks to a number of well-preserved specimens, including individuals found in brooding positions atop nests of eggs, though most of them were initially referred to the related Oviraptor. These nesting specimens have helped to solidify the link between non-avian dinosaurs and birds.
The Barun Goyot Formation is a geological formation dating to the Late Cretaceous Period. It is located within and is widely represented in the Gobi Desert Basin, in the Ömnögovi Province of Mongolia.
The Nemegt Formation is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds.
Tsaagan is a genus of dromaeosaurid dinosaur from the Djadokhta Formation of the Late Cretaceous of Mongolia.
Minotaurasaurus is a monospecific genus of ankylosaurid dinosaur that lived in Mongolia during the Late Cretaceous in what is now the Djadochta Formation. The type and only species, Minotaurasaurus ramachandrani, is known from two skulls, a cervical vertebra and a cervical half ring. It was named and described in 2009 by Clifford Miles and Clark Miles. The first fossils of Minotaurasaurus were illegally exported out of Mongolia.It has been suggested to be a synonym of Tarchia but more recent publications consider it as a distinct genus.
Kol is an extinct genus of coelurosaurian theropod dinosaur from the Late Cretaceous of Mongolia. The type and only species is Kol ghuva. The type specimen was excavated from the Ukhaa Tolgod locality of the Djadochta Formation, dating to about 75 million years ago. It is believed to have been about twice the size of the contemporaneous Shuvuuia. However, unlike Shuvuuia, which is known from many well preserved specimens, and although Ukhaa Tolgod has been thoroughly explored, Kol is known only from one complete foot, suggesting that it must have been relatively rare in that ecosystem.
Aiolosaurus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, Aiolosaurus oriens, was named in 2000 from Ukhaa Tolgod, a rich fossil site in the Campanian-age Djadochta Formation.
Priscagamidae is an extinct family of iguanian lizards known from the Late Cretaceous of Mongolia and China and the Eocene of India, spanning a range from 83.6 to 48.6 million years ago. Probably the earliest priscagamids on indeterminate genera were found in Aptian-Albian sediments in "Hobur", Mongolia. It includes the genera Heterodontagama, Mimeosaurus, Phrynosomimus, Priscagama, and possibly Pleurodontagama. The first fossils of priscagamids were found in the Djadochta and Khermeen Tsav formations of Mongolia. More recently they have been found in the Cambay Formation in India, leading to the naming of Heterodontagama in 2013. Priscagamidae was originally described as a subfamily of Agamidae called Priscagaminae in 1984, but it was reclassified as a distinct family in 1989. Most phylogenetic analyses still find a close relationship between Priscagamidae and Agamidae, although a 2015 study found it to be basal to all other iguanian clades, warranting its removal from Iguania and placement in a larger clade called Iguanomorpha.
Saichangurvel is an extinct genus of iguanian lizards from the Late Cretaceous of Mongolia. It is a member of a clade called Gobiguania, an exclusively Late Cretaceous group of iguanian lizards that was likely endemic to the Gobi Desert. The type species, Saichangurvel davidsoni, was named by paleontologists Jack Conrad and Mark Norell of the American Museum of Natural History in 2007. It is known from a single nearly complete and fully articulated skeleton called IGM 3/858, which was found eroding from a block of sandstone during a thunderstorm at a fossil locality called Ukhaa Tolgod. IGM 3/858 comes from the Djadochta Formation, which is between 75 and 71 million years in age. Just as it is today, the Gobi was a desert during the Cretaceous. IGM 3/858 may have died in a collapsing sand dune, the rapid burial preserving its skeleton in pristine condition.
Almas is a genus of troodontid theropod dinosaur from the Late Cretaceous of Mongolia. It contains a single species, Almas ukhaa, named in 2017 by Pei Rui and colleagues, based on a partial articulated skeleton. The only known specimen was found in the Djadochta Formation, which is late Campanian in age.
The Javkhlant Formation is a geological formation in Mongolia whose strata date back to the Late Cretaceous possibly Santonian to Campanian. Ceratopsian, ornithopod and theropod remains been found in the formation. A prominent fossilized therizinosauroid nesting site is also known from the formation.
Natovenator is a genus of halszkaraptorine dromaeosaurid dinosaur from the Late Cretaceous Barun Goyot Formation of Mongolia. The genus is known from a single species, N. polydontus. Natovenator is crucial to the understanding of halszkaraptorines due to it providing more support for the semi-aquatic lifestyle that has been proposed for this clade. This discovery is important as the semi-aquatic lifestyles of halszkaraptorines was contested in early 2022.