Bagaraatan (/'ba-ɣa-raa-tan/ meaning 'small' baɣa + 'carnivorous animal, beast of prey' araatan in Mongolian) is a genus of theropod dinosaur from the Late Cretaceous period. Its fossils were found in the Nemegt Formation of Mongolia. Bagaraatan may have been around 3 to 4 metres (9.8 to 13 ft) in length.

The type species, B. ostromi, was described by Osmolska in 1996. The post-cranial (ZPAL MgD-I/108) skeleton has been described as "bird-like", while the skull exhibits features of several different theropod groups.

Temporal range: Late Cretaceous, 70 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Superfamily: Tyrannosauroidea
Genus: Bagaraatan
Osmolska, 1996
Type species
Bagaraatan ostromi
Osmolska, 1996


Bagaraatan size diagram
Size of Bagaraatan ostromi compared to a human
Bagaraatan ostromi
Caudal vertebra

Holtz classified Bagaraatan as a basal tyrannosauroid, Coria identified it as a troodontid, and Rauhut placed it in Maniraptora.[1] Mark Loewen et al. placed it in basal Tyrannosauroidea, agreeing with the placement by Holtz.[2]

Below is the cladogram by Loewen et al. in 2013.[2]


Proceratosaurus bradleyi

Kileskus aristotocus

Guanlong wucaii

Sinotyrannus kazuoensis

Juratyrant langhami

Stokesosaurus clevelandi

Dilong paradoxus

Eotyrannus lengi

Bagaraatan ostromi

Raptorex kriegsteini

Dryptosaurus aquilunguis

Alectrosaurus olseni

Xiongguanlong baimoensis

Appalachiosaurus montgomeriensis

Alioramus altai

Alioramus remotus



  1. ^ O. W. M. Rauhut (2003). The interrelationships and evolution of basal theropod dinosaurs. Special Papers in Palaeontology 69: 1-213.
  2. ^ a b Loewen, M.A.; Irmis, R.B.; Sertich, J.J.W.; Currie, P. J.; Sampson, S. D. (2013). Evans, David C, ed. "Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans". PLoS ONE. 8 (11): e79420. doi:10.1371/journal.pone.0079420. PMC 3819173. PMID 24223179.


  • Osmolska, H. (1996). "An unusual theropod dinosaur from the Late Cretaceous Nemegt Formation of Mongolia". Acta Palaeontologica Polonica 41; 1-38 [1]

External links


Alioramus (; meaning 'different branch') is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. The type species, A. remotus, is known from a partial skull and three foot bones recovered from Mongolian sediments which were deposited in a humid floodplain about 70 million years ago. These remains were named and described by Soviet paleontologist Sergei Kurzanov in 1976. A second species, A. altai, known from a much more complete skeleton, was named and described by Stephen L. Brusatte and colleagues in 2009. Its relationships to other tyrannosaurid genera are unclear, with some evidence supporting a hypothesis that Alioramus is closely related to the contemporary species Tarbosaurus bataar.

Alioramus were bipedal like all known theropods, and their sharp teeth indicate that they were carnivores. Known specimens were smaller than other tyrannosaurids like Tarbosaurus bataar and Tyrannosaurus rex, but their adult size is difficult to estimate since both Alioramus species are known only from juvenile or sub-adult remains. The recent discovery of Qianzhousaurus indicates that it belongs to a distinct branch of tyrannosaur. The genus Alioramus is characterized by a row of five bony crests along the top of the snout, a greater number of teeth than any other genus of tyrannosaurid, and a lower skull than most other tyrannosaurids.


Appalachiosaurus ( ap-ə-LAY-chee-o-SAWR-əs; "Appalachian lizard") is a genus of tyrannosauroid theropod dinosaur from the Late Cretaceous Period of eastern North America. Like almost all theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal over 7 meters (23 ft) long and weighing over 600 kilograms (1300 lb), which indicates an adult would have been even larger. It is the most completely known theropod from the eastern part of North America.

Fossils of Appalachiosaurus were found in central Alabama, from the Demopolis Chalk Formation. This formation dates to the middle of the Campanian stage of the Late Cretaceous, or around 77 million years ago. Fossil material assigned to A. montegomeriensis is also known from the Donoho Creek and Tar Heel-Coachman formations of North and South Carolina.


Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.

Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrannosaurs, ornithomimosaurs, and maniraptorans; Maniraptora includes birds, the only dinosaur group alive today.Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie considers it probable that all coelurosaurs were feathered. In the past, Coelurosauria was used to refer to all small theropods, but this classification has since been abolished.

Dilong paradoxus

Dilong (帝龍, which means 'emperor dragon') is a genus of basal tyrannosauroid dinosaur. The only species is Dilong paradoxus. It is from the Lower Cretaceous Yixian Formation near Lujiatun, Beipiao, in the western Liaoning province of China. It lived about 126 million years ago.


Dryptosaurus ( DRIP-toh-SOR-əs) is a genus of tyrannosauroid that lived approximately 67 million years ago during the latter part of the Cretaceous period in what is now New Jersey. Dryptosaurus was a large, bipedal, ground-dwelling carnivore, that could grow up to 7.5 m (24.6 ft) long. Although largely unknown now outside of academic circles, a famous painting of the genus by Charles R. Knight made it one of the more widely known dinosaurs of its time, in spite of its poor fossil record. First described by Edward Drinker Cope in 1866 and later renamed by Othniel C. Marsh in 1877, Dryptosaurus is among the first theropod dinosaurs known to science.


Eotyrannus (meaning "dawn tyrant") is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. The etymology of the generic name refers to the animals classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.

Halszka Osmólska

Halszka Osmólska (September 15, 1930 – March 31, 2008) was a Polish paleontologist who had specialized in Mongolian dinosaurs.


Juratyrant (meaning "Jurassic tyrant") is a tyrannosauroid dinosaur genus from the late Jurassic period (early Tithonian age) of England. The genus contains a single species, J. langhami.


Kileskus (meaning lizard in the Khakas language) is a genus of tyrannosauroid dinosaur known from partial remains found in Middle Jurassic (Bathonian stage) Itat Formation of Krasnoyarsk Krai, Russia. Fossils recovered include the holotype maxilla, a premaxilla, a surangular, and a few bones from the hand and foot. The skull bones are similar to those of Proceratosaurus. The type species is K. aristotocus. Kileskus was named in 2010 by Averianov and colleagues.

Nemegt Formation

The Nemegt Formation (or Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. It overlies and sometimes interfingers with the Barun Goyot Formation. Interfingering has been noted at the stratotype (Red Walls) and Khermeen Tsav. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, and a diverse fauna of dinosaurs, including birds. The climate associated with it was wetter than when preceding formations were deposited; there seems to have existed at least some degree of forest cover. Fossilized trunks have been also found.

There has been no absolute dating of the Nemegt Formation. It is, however, almost certainly early Maastrichtian c 71-70 Ma. Gradzinski and others considered a Campanian age possible but more recent research indicates otherwise. A Campanian age no longer seems credible, because the Alagteegian (or lower Djadokhtan, at the locality "Chuluut Uul") has been radiometrically dated at about 73.5 Ma or even younger (a more recent K/Ar date is 71.6 +/- 1.6 Ma). The c 73.5 (or perhaps 72) Ma Alagteegian is separated from the Nemegt by the "classic" Djadokhtan (e.g. Bayan Dzag), later Djadohktan (represented by Ukhaa Tolgod) and Barungoyotian (Khulsan). All these intervening horizons almost certainly represent more than the 1.5 million years between the dated Alagteegian level and the onset of Maastrichtian time (72.1 million Ma according to current dating). Ergo the Nemegt is entirely Maastrichtian. See also Shuvalov, Sochava and Martinsson The Age of Dinosaurs in Russia and Mongolia. The presence of Saurolophus further supports an early Maastrichtian age as the same genus occurs in the early Maastrichtian Horseshoe Canyon formation.


Proceratosaurus is a genus of small-sized (~3 metres (9.8 ft) long) carnivorous theropod dinosaur from the Middle Jurassic (Bathonian) of England. It was originally thought to be an ancestor of Ceratosaurus, due to the similar small crest on its snout. Now, however, it is considered a coelurosaur, specifically one of the earliest known members of Tyrannosauroidea, the clade of basal relatives of the tyrannosaurs.The type specimen is held in the London Museum of Natural History and was recovered in 1910 at Minchinhampton while excavating for a reservoir.


Raptorex is a dubious genus of tyrannosaurid dinosaur. Its fossil remains consist of a single juvenile specimen probably uncovered in Mongolia, or possibly northeastern China. The type species is R. kriegsteini, described in 2009 by Sereno and colleagues. The genus name is derived from Latin raptor, "robber", and rex, "king". The specific name honours Roman Kriegstein, a survivor of the Holocaust, whose son Henry Kriegstein donated the specimen to the University of Chicago for scientific study.While initially considered to have come from the Yixian Formation of China, dated to approximately 125 million years ago during the early Cretaceous period, later studies showed that such an early date for the fossil are unlikely, and given its extremely close similarity to juvenile tyrannosaurids of the late Cretaceous, it probably came from the Iren Dabasu or similar formation. Because the specimen is a juvenile, and the changes undergone by tyrannosaurids during growth are not yet well understood, many researchers now consider it to be a nomen dubium, because it cannot be confidently paired with an adult skeleton (though it is extremely similar to juvenile Tarbosaurus bataar skeletons of the same size and age).


Saurolophus (; meaning "lizard crest") is a genus of large saurolophine hadrosaurid dinosaurs that lived about 70.0–68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back from the skull. Saurolophus was a herbivorous dinosaur which could move about either bipedally or quadrupedally.

The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.


Sinotyrannus (meaning "Chinese tyrant") is a genus of large basal proceratosaurid dinosaur, a relative of tyrannosaurids which flourished in North America and Asia during the Jurassic and early Cretaceous periods. Sinotyrannus is known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Though it is not much younger than primitive tyrannosauroids such as Dilong, it is similar in size to later forms such as Tyrannosaurus. It was much larger than contemporary tyrannosauroids; reaching a total estimated length of 9–10 m (30–33 ft), it is the largest known theropod from the Jiufotang Formation. The type species is S. kazuoensis, described by Ji et al., in 2009.


Stokesosaurus (meaning "Stokes' lizard") is a genus of small (around 3 to 4 meters (10 to 13 ft) in length), carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States.

Timeline of tyrannosaur research

This timeline of tyrannosaur research is a chronological listing of events in the history of paleontology focused on the tyrannosaurs, a group of predatory theropod dinosaurs that began as small, long-armed bird-like creatures with elaborate cranial ornamentation but achieved apex predator status during the Late Cretaceous as their arms shrank and body size expanded. Although formally trained scientists did not begin to study tyrannosaur fossils until the mid-19th century, these remains may have been discovered by Native Americans and interpreted through a mythological lens. The Montana Crow tradition about thunder birds with two claws on their feet may have been inspired by isolated tyrannosaurid forelimbs found locally. Other legends possibly inspired by tyrannosaur remains include Cheyenne stories about a mythical creature called the Ahke, and Delaware stories about smoking the bones of ancient monsters to have wishes granted.Tyrannosaur remains were among the first dinosaur fossils collected in the United States. The first of these was named Deinodon horridus by Joseph Leidy. However, as this species was based only on teeth the name would fall into disuse. Soon after, Edward Drinker Cope described Laelaps aquilunguis from a partial skeleton in New Jersey. Its discovery heralded the realization that carnivorous dinosaurs were bipeds, unlike the lizardlike megalosaurs sculpted for the Crystal Palace. Laelaps was also among the first dinosaurs to be portrayed artistically as a vigorous, active animal, presaging the Dinosaur Renaissance by decades. Later in the century, Cope's hated rival Othniel Charles Marsh would discover that the name Laelaps had already been given to a parasitic mite, and would rename the dinosaur Dryptosaurus.Early in the 20th century, Tyrannosaurus itself was discovered by Barnum Brown and named by Henry Fairfield Osborn, who would recognize it as a representative of a distinct family of dinosaurs he called the Tyrannosauridae. Tyrannosaur taxonomy would be controversial for many decades afterward. One controversy centered around the use of the name Tyrannosauridae for this family, as the name "Deinodontidae" had already been proposed. The name Tyrannosauridae came out victorious following arguments put forth by Dale Russell in 1970. The other major controversy regarding tyrannosaur taxonomy was the family's evolutionary relationships. Early in the history of paleontology, it was assumed that the large carnivorous dinosaurs were all part of one evolutionary lineage ("carnosaurs"), while the small carnivorous dinosaurs were part of a separate lineage (coelurosaurs). Tyrannosaurid anatomy led some early researchers like Matthew, Brown, and Huene, to cast doubt on the validity of this division. However, the traditional carnosaur-coelurosaur division persisted until the early 1990s, when the application of cladistics to tyrannosaur systematics confirmed the doubts of early workers and found tyrannosaurs to be large-bodied coelurosaurs.Another debate about tyrannosaurs would not be settled until the early 21st century: their diet. Early researchers were so overwhelmed by the massive bulk of Tyrannosaurus that some, like Lawrence Lambe, were skeptical that it was even capable of hunting down live prey and assumed that it lived as a scavenger. This view continued to be advocated into the 1990s by Jack Horner but was shown false by Kenneth Carpenter, who reported the discovery of a partially healed tyrannosaur bite wound on an Edmontosaurus annectens tail vertebra, proving that T. rex at least sometimes pursued living victims.


Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe, Asia, South America and Australia.

Tyrannosauroids were bipedal carnivores, as were most theropods, and were characterized by numerous skeletal features, especially of the skull and pelvis. Early in their existence, tyrannosauroids were small predators with long, three-fingered forelimbs. Late Cretaceous genera became much larger, including some of the largest land-based predators ever to exist, but most of these later genera had proportionately small forelimbs with only two digits. Primitive feathers have been identified in fossils of two species, and may have been present in other tyrannosauroids as well. Prominent bony crests in a variety of shapes and sizes on the skulls of many tyrannosauroids may have served display functions.


Xinjiangovenator (meaning "Xinjiang hunter") is a genus of coelurosaurian dinosaurs, possibly part of the group Maniraptora, which lived during the Early Cretaceous period, sometime between the Valanginian and Albian stages. The remains of Xinjiangovenator were found in the Lianmuqin Formation of Wuerho, Xinjiang, China, and were first described by Dong Zhiming in 1973. The genus is based on a single specimen, an articulated partial right lower leg, containing the tibia, three pieces of the fibula, the calcaneum and the astragalus. This specimen, IVPP V4024-2, is the holotype of the genus.The holotype was originally thought to be another specimen of Phaedrolosaurus. However, Phaedrolosaurus is based only on a non-diagnostic tooth, so the hindlimb bones were given their own genus by Oliver Rauhut and Xu Xing in 2005. The type species is Xinjiangovenator parvus. The generic name is derived from the autonomous region of Xinjiang and Latin venator, "hunter". The specific name parvus means "small" in Latin.The lower leg (tibia plus ankle bones) has a length of 312 millimeters (12.3 inches). Gregory S. Paul estimated in 2010 that Xinjiangovenator individuals had a length of 3 meters and a mass of 70 kg. Rauhut & Xu (2005) established two autapomorphies (unique derived traits) that could be used to characterize Xinjiangovenator. First, the lateral condyle (outer ankle joint) at the lower end of the tibia extends further backwards than the outer edge of the portion of the tibia near the knee. Secondly, the proximal part of the fibula (near the knee) has a longitudinal groove along its front edge.


Xiongguanlong ("Grand Pass dragon") is a genus of tyrannosauroid dinosaur that lived in the Early Cretaceous of what is now China. The type species is X. baimoensis, described online in 2009 by a group of researchers from China and the United States, and formally published in January 2010. The genus name refers to the city of Jiayuguan, a city in northwestern China. The specific name is derived from bai mo, "white ghost", after the "white ghost castle", a rock formation near the fossil site. The fossils include a skull, vertebrae, a right ilium and the right femur. The rocks it was found in are from the Aptian to Albian stages of the Cretaceous, between 125 and 100 million years ago.

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