Tarbosaurus
Encyclopedia
Tarbosaurus is a genus
of tyrannosaurid theropod dinosaur that flourished in Asia
about 70 million years ago, at the end of the Late Cretaceous
Period. Fossil
s have been recovered in Mongolia
, with more fragmentary remains found further afield in parts of China
. Although many species
have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts contend that this species is actually an Asian representative of the North America
n genus Tyrannosaurus
; if true, this would invalidate the genus Tarbosaurus altogether.
Tarbosaurus and Tyrannosaurus are considered to be at least closely related genera, if not synonymous
. Alioramus
, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large biped
al predator
, weighing more than a ton and equipped with dozens of large, sharp teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs.
Tarbosaurus lived in a humid floodplain
criss-crossed by river channels. In this environment, it was an apex predator
at the top of the food chain
, probably preying on other large dinosaurs like the hadrosaur Saurolophus
or the sauropod Nemegtosaurus
. Tarbosaurus is very well represented in the fossil
record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure.
Although smaller than Tyrannosaurus, Tarbosaurus was one of the largest tyrannosaurids. The largest known individuals were between 10 and 12 meters (30 to 40 ft) long. The mass of a fully grown individual is considered comparable to or slightly smaller than Tyrannosaurus.
The largest known Tarbosaurus skull is more than 1.3 meters (4 ft) long, larger than all other tyrannosaurids except Tyrannosaurus. The skull was tall, like that of Tyrannosaurus, but not as wide, especially towards the rear. The unexpanded rear of the skull meant that Tarbosaurus eyes did not face directly forwards, suggesting that it lacked the binocular vision
of Tyrannosaurus. Large fenestrae (openings) in the skull reduced its weight. Between 60 and 64 teeth lined its jaws, slightly more than in Tyrannosaurus but fewer than in smaller tyrannosaurids like Gorgosaurus
and Alioramus. Most of its teeth were oval in cross section
, although the teeth of the premaxilla
at the tip of the upper jaw had a D-shaped cross section. This heterodonty is characteristic of the family. The longest teeth were in the maxilla
(upper jaw bone), with crowns up to 85 millimeters (3.3 in) long. In the lower jaw
, a ridge on the outer surface of the angular
bone articulated with the rear of the dentary bone, creating a locking mechanism unique to Tarbosaurus and Alioramus. Other tyrannosaurids lacked this ridge and had more flexibility in the lower jaw.
Tyrannosaurids varied little in body form, and Tarbosaurus was no exception. The head was supported by an S-shaped neck, while the rest of the vertebral column
, including the long tail, was held horizontally. Tarbosaurus had tiny forelimbs, proportionably to body size the smallest of all members of the family. The hands had two clawed digits each, with an additional unclawed third metacarpal found in some specimens, similar to closely related genera. Holtz has suggested that Tarbosaurus also has a theropod reduction of fingers IV-I "developed further" than in other tyrannosaurids, as the second metacarpal in the Tarbosaurus specimens he studied is less than twice the length of the first metacarpal (other tyrannosaurids have a second metacarpal about twice the length of the first metacarpal). Also, the third metacarpal in Tarbosaurus is proportionally shorter than in other tyrannosaurids; in other tyrannosaurids (like Albertosaurus
and Daspletosaurus
), the third metacarpal is often longer than the first metacarpal, while in Tarbosaurus, the third metacarpal is shorter than the first.
In contrast to the forelimbs, the three-toed hindlimbs were long and thick, supporting the body in a bipedal posture. The long, heavy tail served as a counterweight
to the head and torso and placed the center of gravity
over the hips.
Carr
et al. 2005
*Note: Carr et al. use the name Tyrannosaurus bataar
Currie
et al. 2003
Tarbosaurus is classified as a theropod in the subfamily Tyrannosaurinae within the family Tyrannosauridae
. Other members include Tyrannosaurus and the earlier Daspletosaurus
, both from North America, and possibly the Mongolian genus Alioramus. Animals in this subfamily are more closely related to Tyrannosaurus than to Albertosaurus
and are known for their robust build with proportionally larger skulls and longer femur
s than in the other subfamily, the Albertosaurinae.
Tarbosaurus bataar was originally described as a species of Tyrannosaurus, an arrangement that has been supported by more recent studies. Others prefer to keep the genera separate, while still recognizing them as sister taxa. A 2003 cladistic analysis based on skull features instead identified Alioramus as the closest known relative of Tarbosaurus, as the two genera share skull characteristics that are related to stress distribution and that are not found in other tyrannosaurines. If proven, this relationship would preclude Tarbosaurus from becoming a synonym for Tyrannosaurus and would suggest that separate tyrannosaurine lineages evolved
in Asia and North America. The two known specimens of Alioramus, which shows juvenile characteristics, is not likely a juvenile Tarbosaurus because of its much higher tooth count (76 to 78 teeth) and the unique row of bony bumps along the top of its snout.
In 1946, a joint Soviet-Mongolian expedition to the Gobi Desert
in the Mongolian Ömnögovi Province
turned up a large theropod skull and some vertebrae in the Nemegt Formation
. In 1955, Evgeny Maleev
, a Russian paleontologist, made this specimen the holotype
(PIN 551-1) of a new species, which he called Tyrannosaurus bataar. The species name is a misspelling of the Mongolian баатар/baatar ("hero"). In the same year, Maleev also described and named three new theropod skulls, each associated with skeletal remains discovered by the same expedition in 1948 and 1949. The first of these (PIN 551-2) was named Tarbosaurus efremovi, a new generic name composed of the Ancient Greek
ταρβος/tarbos ("terror", "alarm", "awe", or "reverence") and σαυρος/sauros ("lizard"), and the species named after Ivan Yefremov, a Russian paleontologist and science fiction
author. The other two (PIN 553-1 and PIN 552-2) were also named as new species and assigned to the North American genus Gorgosaurus (G. lancinator and G. novojilovi, respectively). All three of these latter specimens are smaller than the first.
A 1965 paper by A.K. Rozhdestvensky
recognized all of Maleev's specimens as different growth stages
of the same species, which he believed to be distinct from the North American Tyrannosaurus. He created a new combination, Tarbosaurus bataar, to include all the specimens described in 1955 as well as newer material. Later authors, including Maleev himself, agreed with Rozhdestvensky's analysis, although some used the name Tarbosaurus efremovi rather than T. bataar. American paleontologist Kenneth Carpenter
re-examined the material in 1992. He concluded that it belonged to the genus Tyrannosaurus, as originally published by Maleev, and lumped all the specimens into the species Tyrannosaurus bataar except the remains that Maleev had named Gorgosaurus novojilovi. Carpenter thought this specimen represented a separate, smaller genus of tyrannosaurid, which he called Maleevosaurus novojilovi. George Olshevsky
created the new generic name Jenghizkhan (after Genghis Khan
) for Tyrannosaurus bataar in 1995, while also recognizing Tarbosaurus efremovi and Maleevosaurus novojilovi, for a total of three distinct, contemporaneous genera from the Nemegt Formation. A 1999 study subsequently reclassified Maleevosaurus as a juvenile Tarbosaurus. All research published since 1999 recognizes only a single species, which is either called Tarbosaurus bataar or Tyrannosaurus bataar.
After the original Russian-Mongolian expeditions in the 1940s, Polish
-Mongolian joint expeditions to the Gobi Desert began in 1963 and continued until 1971, recovering many new fossils, including new specimens of Tarbosaurus from the Nemegt Formation. Expeditions involving Japan
ese and Mongolian scientists between 1993 and 1998, as well as private expeditions hosted by Canadian
paleontologist Phil Currie
around the turn of the 21st century, discovered and collected further Tarbosaurus material. More than 30 specimens are known, including more than 15 skulls and several complete postcranial skeletons.
paleontologists discovered a partial skull and skeleton of a small theropod (IVPP
V4878) in the Xinjiang
Autonomous Region of China in the mid-1960s. In 1977, Dong Zhiming
described this specimen, which was recovered from the Subashi Formation
, as a new genus and species, Shanshanosaurus huoyanshanensis. Gregory Paul recognized Shanshanosaurus as a tyrannosaurid in 1988, referring it to the now-defunct genus Aublysodon
. Dong and Currie later re-examined the specimen and deemed it to be a juvenile of a larger species of tyrannosaurid. These authors refrained from assigning it to any particular genus but suggested Tarbosaurus as a possibility. Over the years, other Chinese localities have produced tyrannosaurid teeth and fragmentary remains, several of which have been given names. Albertosaurus periculosis, Tyrannosaurus luanchuanensis, Tyrannosaurus turpanensis and Chingkankousaurus fragilis
are often considered synonyms of Tarbosaurus.
Named in 1976 by Sergei Kurzanov
, Alioramus
is another genus of tyrannosaurid from slightly older sediments in Mongolia. Several analyses have concluded Alioramus was quite closely related to Tarbosaurus. It was described as an adult, but its long, low skull is characteristic of a juvenile tyrannosaurid. This led Currie to speculate that Alioramus might represent a juvenile Tarbosaurus, but he noted that the much higher tooth count and row of crests on top of the snout suggested otherwise.
Like several other large tyrannosaurids, Tarbosaurus is known from relatively abundant and well-preserved fossil material. In fact, one quarter of all fossils collected from the Nemegt Formation belong to Tarbosaurus. Although Tarbosaurus has not been studied as thoroughly as the North American tyrannosaurids, the available material has allowed scientists to draw limited conclusions about its biology.
was transmitted up through the maxilla, the primary tooth-bearing bone of the upper jaw, into surrounding skull bones. In North American tyrannosaurids, this force went from the maxilla into the fused nasal bone
s on top of the snout, which were firmly connected in the rear to the lacrimal bone
s by bony struts. These struts locked the two bones together, suggesting that force was then transmitted from the nasals to the lacrimals.
Tarbosaurus lacked these bony struts, and the connection between the nasals and lacrimals was weak. Instead, a backwards projection of the maxilla was massively developed in Tarbosaurus and fit inside a sheath formed from the lacrimal. This projection was a thin, bony plate in North American tyrannosaurids. The large backwards projection suggests that force was transmitted more directly from the maxilla to the lacrimal in Tarbosaurus. The lacrimal was also more firmly anchored to the frontal
and prefrontal bone
s in Tarbosaurus. The well-developed connections between the maxilla, lacrimal, frontal and prefrontal would have made its entire upper jaw more rigid.
Another major difference between Tarbosaurus and its North American relatives was its more rigid mandible (lower jaw). While many theropods, including North American tyrannosaurids, had some degree of flexibility between the bones in the rear of the mandible and the dentary in the front, Tarbosaurus had a locking mechanism formed from a ridge on the surface of the angular, which articulated with a square process on the rear of the dentary.
Some scientists have hypothesized
that the more rigid skull of Tarbosaurus was an adaptation to hunting the massive titanosaurid sauropods found in the Nemegt Formation, which did not exist in most of North America during the Late Cretaceous. The differences in skull mechanics also have an impact on tyrannosaurid phylogeny. Tarbosaurus-like articulations between the skull bones are also seen in Alioramus from Mongolia, suggesting that it, and not Tyrannosaurus, is the closest relative of Tarbosaurus. Similarities between Tarbosaurus and Tyrannosaurus might therefore be related to their large size, independently developed through convergent evolution
.
, called an endocast, of the inside of this cavity allowed Maleev to make preliminary observations about the shape of a Tarbosaurus brain. A newer polyurethane
rubber cast allowed a more detailed study of Tarbosaurus brain structure and function.
Tyrannosaurus rex brain structure has also been analyzed, and Tarbosaurus was similar, differing only in the positions of some cranial nerve roots, including the trigeminal
and accessory nerve
s. Tyrannosaurid brains were more similar to those of crocodilia
ns and other reptile
s than to bird
s. The total brain volume for a 12 meter (40 ft) Tarbosaurus is estimated at only 184 cubic centimeters (11.2 cu in). The large size of the olfactory bulb
s, as well as the terminal and olfactory nerve
s, suggest that Tarbosaurus had a keen sense of smell, as was also the case with Tyrannosaurus. The vomeronasal bulb is large and differentiated from the olfactory bulb, indicating a well-developed Jacobsen's organ, which was used to detect pheromone
s. This may imply that Tarbosaurus had complex mating behavior. The auditory nerve was also large, suggesting good hearing
, which may have been useful for auditory communication
and spatial awareness. The nerve had a well-developed vestibular
component as well, which implies a good sense of balance and coordination. In contrast, the nerves and brain structures associated with eyesight were smaller and undeveloped. The midbrain tectum
, responsible for visual processing in reptiles, was very small in Tarbosaurus, as were the optic nerve
and the oculomotor nerve
, which controls eye movement. Unlike Tyrannosaurus, which had forward-facing eyes that provided some degree of binocular vision, Tarbosaurus had a narrower skull more typical of other tyrannosaurids in which the eyes faced primarily sideways. All of this suggests that Tarbosaurus relied more on its senses of smell and hearing than on its eyesight.
The vast majority of known Tarbosaurus fossils were recovered from the Nemegt Formation
in the Gobi Desert
of southern Mongolia. This geologic formation
has never been dated radiometrically
, but the fauna
present in the fossil record indicate it was probably deposited during the early Maastrichtian
stage, at the end of the Late Cretaceous
about 70 million years ago. The Subashi Formation
, in which Shanshanosaurus remains were discovered, is also Maastrichtian in age.
Nemegt sediments preserve large river channels and soil deposits that indicate a far more humid climate than those suggested by the underlying Barun Goyot
and Djadochta Formation
s. However, caliche
deposits indicate at least periodic droughts. Sediment was deposited in the channels and floodplains of large rivers. Occasional mollusc fossils are found, as well as a variety of other aquatic animals like fish and turtles. Crocodilians included several species of Shamosuchus
, a genus with teeth adapted for crushing shells. Mammal
fossils are exceedingly rare in the Nemegt Formation, but many birds have been found, including the enantiornithine Gurilynia
and the hesperornithiform
Judinornis
, as well as Teviornis
, an early representative of the still-existing Anseriformes
(waterfowl), a bird order. Scientists have described many dinosaurs from the Nemegt Formation, including ankylosaurids such as Tarchia
, and pachycephalosaurs such as Homalocephale
and Prenocephale
. By far the largest predator known from the formation, adult Tarbosaurus most likely preyed upon large hadrosaurs such as Saurolophus
and Barsboldia
, or sauropods such as Nemegtosaurus, and Opisthocoelicaudia
. Adults would have received little competition from small theropods such as troodontids (Borogovia
, Tochisaurus
, Saurornithoides
), oviraptorosaurs (Elmisaurus
, Nemegtomaia
, Rinchenia
) or Bagaraatan
, sometimes considered a basal
tyrannosauroid. Other theropods, like the gigantic Therizinosaurus
, may have been herbivorous
, and ornithomimosaurs such as Anserimimus
, Gallimimus
, and Deinocheirus
might have been omnivores that only took small prey and were therefore no competition for Tarbosaurus. However, as in other large tyrannosaurids as well as modern Komodo dragon
s, juveniles and subadult Tarbosaurus may have filled niches between the massive adults and these smaller theropods.
Readable material.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of tyrannosaurid theropod dinosaur that flourished in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
about 70 million years ago, at the end of the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s have been recovered in Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
, with more fragmentary remains found further afield in parts of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Although many species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts contend that this species is actually an Asian representative of the North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n genus Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
; if true, this would invalidate the genus Tarbosaurus altogether.
Tarbosaurus and Tyrannosaurus are considered to be at least closely related genera, if not synonymous
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
. Alioramus
Alioramus
Alioramus is a genus of tyrannosaurid theropod dinosaur from the Late Cretaceous period of Asia. The type A. remotus, is known from a partial skull and three metatarsals recovered from Mongolian sediments which were deposited in a humid floodplain between 70 and 65 million years ago. These...
, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large biped
Biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al predator
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, weighing more than a ton and equipped with dozens of large, sharp teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs.
Tarbosaurus lived in a humid floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
criss-crossed by river channels. In this environment, it was an apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
at the top of the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
, probably preying on other large dinosaurs like the hadrosaur Saurolophus
Saurolophus
Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 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...
or the sauropod Nemegtosaurus
Nemegtosaurus
Nemegtosaurus was a sauropod dinosaur from Late Cretaceous Period of what is now Mongolia. It was named after the Nemegt Basin in the Gobi Desert, where the remains — a single skull — were found...
. Tarbosaurus is very well represented in the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure.
Description
The largest known Tarbosaurus skull is more than 1.3 meters (4 ft) long, larger than all other tyrannosaurids except Tyrannosaurus. The skull was tall, like that of Tyrannosaurus, but not as wide, especially towards the rear. The unexpanded rear of the skull meant that Tarbosaurus eyes did not face directly forwards, suggesting that it lacked the binocular vision
Binocular vision
Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
of Tyrannosaurus. Large fenestrae (openings) in the skull reduced its weight. Between 60 and 64 teeth lined its jaws, slightly more than in Tyrannosaurus but fewer than in smaller tyrannosaurids like Gorgosaurus
Gorgosaurus
Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.5 and 75 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana....
and Alioramus. Most of its teeth were oval in cross section
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...
, although the teeth of the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
at the tip of the upper jaw had a D-shaped cross section. This heterodonty is characteristic of the family. The longest teeth were in the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
(upper jaw bone), with crowns up to 85 millimeters (3.3 in) long. In the lower jaw
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
, a ridge on the outer surface of the angular
Angular
The angular is a large bone in the lower jaw of amphibians and reptiles , which is connected to all other lower jaw bones: the dentary , the splenial, the suprangular, and the articular...
bone articulated with the rear of the dentary bone, creating a locking mechanism unique to Tarbosaurus and Alioramus. Other tyrannosaurids lacked this ridge and had more flexibility in the lower jaw.
Tyrannosaurids varied little in body form, and Tarbosaurus was no exception. The head was supported by an S-shaped neck, while the rest of the vertebral column
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
, including the long tail, was held horizontally. Tarbosaurus had tiny forelimbs, proportionably to body size the smallest of all members of the family. The hands had two clawed digits each, with an additional unclawed third metacarpal found in some specimens, similar to closely related genera. Holtz has suggested that Tarbosaurus also has a theropod reduction of fingers IV-I "developed further" than in other tyrannosaurids, as the second metacarpal in the Tarbosaurus specimens he studied is less than twice the length of the first metacarpal (other tyrannosaurids have a second metacarpal about twice the length of the first metacarpal). Also, the third metacarpal in Tarbosaurus is proportionally shorter than in other tyrannosaurids; in other tyrannosaurids (like Albertosaurus
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
and Daspletosaurus
Daspletosaurus
Daspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
), the third metacarpal is often longer than the first metacarpal, while in Tarbosaurus, the third metacarpal is shorter than the first.
In contrast to the forelimbs, the three-toed hindlimbs were long and thick, supporting the body in a bipedal posture. The long, heavy tail served as a counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
to the head and torso and placed the center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
over the hips.
Classification and systematics
Thomas Carr (paleontologist)
Thomas D. Carr is a vertebrate paleontologist who received his Ph.D. from the University of Toronto in 2005. He is now a member of the biology faculty at Carthage College in Kenosha, Wisconsin. Much of his work centers on tyrannosauroid dinosaurs...
et al. 2005
*Note: Carr et al. use the name Tyrannosaurus bataar
Philip Currie
Philip Henry Wodehouse Currie, 1st Baron Currie GCB , known as Sir Philip Currie between 1885 and 1899, was a British diplomat. He was Ambassador to the Ottoman Empire from 1893 to 1898 and Ambassador to Italy from 1898 to 1902.-Background and education:Currie was the son of Raikes Currie, Member...
et al. 2003
Tarbosaurus is classified as a theropod in the subfamily Tyrannosaurinae within the family Tyrannosauridae
Tyrannosauridae
Tyrannosauridae is a family of coelurosaurian theropod dinosaurs which comprises two subfamilies containing up to six genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three...
. Other members include Tyrannosaurus and the earlier Daspletosaurus
Daspletosaurus
Daspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
, both from North America, and possibly the Mongolian genus Alioramus. Animals in this subfamily are more closely related to Tyrannosaurus than to Albertosaurus
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
and are known for their robust build with proportionally larger skulls and longer femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
s than in the other subfamily, the Albertosaurinae.
Tarbosaurus bataar was originally described as a species of Tyrannosaurus, an arrangement that has been supported by more recent studies. Others prefer to keep the genera separate, while still recognizing them as sister taxa. A 2003 cladistic analysis based on skull features instead identified Alioramus as the closest known relative of Tarbosaurus, as the two genera share skull characteristics that are related to stress distribution and that are not found in other tyrannosaurines. If proven, this relationship would preclude Tarbosaurus from becoming a synonym for Tyrannosaurus and would suggest that separate tyrannosaurine lineages evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
in Asia and North America. The two known specimens of Alioramus, which shows juvenile characteristics, is not likely a juvenile Tarbosaurus because of its much higher tooth count (76 to 78 teeth) and the unique row of bony bumps along the top of its snout.
Discovery and naming
Gobi Desert
The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia. The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the...
in the Mongolian Ömnögovi Province
Ömnögovi Province
Ömnögovi is an aimag of Mongolia, located in the south of the country, in the Gobi Desert. Ömnögovi is Mongolia's largest aimag. The capital is Dalanzadgad....
turned up a large theropod skull and some vertebrae in the Nemegt Formation
Nemegt Formation
The Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
. In 1955, Evgeny Maleev
Evgeny Maleev
Evgeny Aleksandrovich Maleev was a Russian paleontologist who named the armoured dinosaur Talarurus, the fearsome Tarbosaurus, and the enigmatic Therizinosaurus. Maleev did research on Tarbosaurus brains by cutting open fossilized braincases with a diamond saw...
, a Russian paleontologist, made this specimen the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
(PIN 551-1) of a new species, which he called Tyrannosaurus bataar. The species name is a misspelling of the Mongolian баатар/baatar ("hero"). In the same year, Maleev also described and named three new theropod skulls, each associated with skeletal remains discovered by the same expedition in 1948 and 1949. The first of these (PIN 551-2) was named Tarbosaurus efremovi, a new generic name composed of the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
ταρβος/tarbos ("terror", "alarm", "awe", or "reverence") and σαυρος/sauros ("lizard"), and the species named after Ivan Yefremov, a Russian paleontologist and science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
author. The other two (PIN 553-1 and PIN 552-2) were also named as new species and assigned to the North American genus Gorgosaurus (G. lancinator and G. novojilovi, respectively). All three of these latter specimens are smaller than the first.
A 1965 paper by A.K. Rozhdestvensky
Anatoly Konstantinovich Rozhdestvensky
Anatoly Konstantinovich Rozhdestvensky was a Russian paleontologist responsible for naming many dinosaurs, including Aralosaurus and Probactrosaurus....
recognized all of Maleev's specimens as different growth stages
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
of the same species, which he believed to be distinct from the North American Tyrannosaurus. He created a new combination, Tarbosaurus bataar, to include all the specimens described in 1955 as well as newer material. Later authors, including Maleev himself, agreed with Rozhdestvensky's analysis, although some used the name Tarbosaurus efremovi rather than T. bataar. American paleontologist Kenneth Carpenter
Kenneth Carpenter
Kenneth Carpenter is a paleontologist. He is the museum director of the USU Eastern Prehistoric Museum and author or co-author of a number of books on dinosaurs and Mesozoic life...
re-examined the material in 1992. He concluded that it belonged to the genus Tyrannosaurus, as originally published by Maleev, and lumped all the specimens into the species Tyrannosaurus bataar except the remains that Maleev had named Gorgosaurus novojilovi. Carpenter thought this specimen represented a separate, smaller genus of tyrannosaurid, which he called Maleevosaurus novojilovi. George Olshevsky
George Olshevsky
George Olshevsky is a freelance editor, writer, publisher, amateur paleontologist, and mathematician living in San Diego, California.Olshevsky maintains the comprehensive online Dinosaur Genera List...
created the new generic name Jenghizkhan (after Genghis Khan
Genghis Khan
Genghis Khan , born Temujin and occasionally known by his temple name Taizu , was the founder and Great Khan of the Mongol Empire, which became the largest contiguous empire in history after his death....
) for Tyrannosaurus bataar in 1995, while also recognizing Tarbosaurus efremovi and Maleevosaurus novojilovi, for a total of three distinct, contemporaneous genera from the Nemegt Formation. A 1999 study subsequently reclassified Maleevosaurus as a juvenile Tarbosaurus. All research published since 1999 recognizes only a single species, which is either called Tarbosaurus bataar or Tyrannosaurus bataar.
After the original Russian-Mongolian expeditions in the 1940s, Polish
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
-Mongolian joint expeditions to the Gobi Desert began in 1963 and continued until 1971, recovering many new fossils, including new specimens of Tarbosaurus from the Nemegt Formation. Expeditions involving Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese and Mongolian scientists between 1993 and 1998, as well as private expeditions hosted by Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
paleontologist Phil Currie
Phil Currie
Philip John Currie, AOE is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton...
around the turn of the 21st century, discovered and collected further Tarbosaurus material. More than 30 specimens are known, including more than 15 skulls and several complete postcranial skeletons.
Possible synonyms
ChineseChina
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
paleontologists discovered a partial skull and skeleton of a small theropod (IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V4878) in the Xinjiang
Xinjiang
Xinjiang is an autonomous region of the People's Republic of China. It is the largest Chinese administrative division and spans over 1.6 million km2...
Autonomous Region of China in the mid-1960s. In 1977, Dong Zhiming
Dong Zhiming
Dong Zhiming , from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, is one of China's leading paleontologists. He began working at the IVPP in 1962, learning from Yang Zhongjian who was director at the time...
described this specimen, which was recovered from the Subashi Formation
Subashi Formation
The Subashi Formation is a late Cretaceous formation from the Xinjiang Autonomous Region of western China. Initially described by Dong Zhiming in 1977, the formation contains remains of Tarbosaurus which were initially described as a separate taxon Shanshanosaurus huoyanshanensis...
, as a new genus and species, Shanshanosaurus huoyanshanensis. Gregory Paul recognized Shanshanosaurus as a tyrannosaurid in 1988, referring it to the now-defunct genus Aublysodon
Aublysodon
Aublysodon is a name given to a large number of carnivorous dinosaur teeth of a certain form found in numerous late Cretaceous period geological formations...
. Dong and Currie later re-examined the specimen and deemed it to be a juvenile of a larger species of tyrannosaurid. These authors refrained from assigning it to any particular genus but suggested Tarbosaurus as a possibility. Over the years, other Chinese localities have produced tyrannosaurid teeth and fragmentary remains, several of which have been given names. Albertosaurus periculosis, Tyrannosaurus luanchuanensis, Tyrannosaurus turpanensis and Chingkankousaurus fragilis
Chingkankousaurus
Chingkankousaurus is the name given to a fossilized bone fragment that probably belonged to a theropod dinosaur from the late Cretaceous Period Wangshi Series of Shandong province in eastern China. It was identified by Yang Zhongjian Chingkankousaurus (named for the Ch'ing-kang-kou village) is...
are often considered synonyms of Tarbosaurus.
Named in 1976 by Sergei Kurzanov
Sergei Kurzanov
Sergei Kurzanov is a Russian paleontologist at the Paleontological Institute of the Russian Academy of Sciences. He is known mainly for his work in Mongolia and the ex-Soviet republics in Central Asia. In 1998, a species of iguanodont dinosaur from Mongolia was named Altirhinus kurzanovi in his...
, Alioramus
Alioramus
Alioramus is a genus of tyrannosaurid theropod dinosaur from the Late Cretaceous period of Asia. The type A. remotus, is known from a partial skull and three metatarsals recovered from Mongolian sediments which were deposited in a humid floodplain between 70 and 65 million years ago. These...
is another genus of tyrannosaurid from slightly older sediments in Mongolia. Several analyses have concluded Alioramus was quite closely related to Tarbosaurus. It was described as an adult, but its long, low skull is characteristic of a juvenile tyrannosaurid. This led Currie to speculate that Alioramus might represent a juvenile Tarbosaurus, but he noted that the much higher tooth count and row of crests on top of the snout suggested otherwise.
Paleobiology
Skull mechanics
The skull of Tarbosaurus was completely described for the first time in 2003. Scientists noted key differences between Tarbosaurus and the North American tyrannosaurids. Many of these differences are related to the handling of stress by the skull bones during a bite. When the upper jaw bit down on an object, forceForce
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
was transmitted up through the maxilla, the primary tooth-bearing bone of the upper jaw, into surrounding skull bones. In North American tyrannosaurids, this force went from the maxilla into the fused nasal bone
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s on top of the snout, which were firmly connected in the rear to the lacrimal bone
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
s by bony struts. These struts locked the two bones together, suggesting that force was then transmitted from the nasals to the lacrimals.
Tarbosaurus lacked these bony struts, and the connection between the nasals and lacrimals was weak. Instead, a backwards projection of the maxilla was massively developed in Tarbosaurus and fit inside a sheath formed from the lacrimal. This projection was a thin, bony plate in North American tyrannosaurids. The large backwards projection suggests that force was transmitted more directly from the maxilla to the lacrimal in Tarbosaurus. The lacrimal was also more firmly anchored to the frontal
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
and prefrontal bone
Prefrontal bone
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles...
s in Tarbosaurus. The well-developed connections between the maxilla, lacrimal, frontal and prefrontal would have made its entire upper jaw more rigid.
Another major difference between Tarbosaurus and its North American relatives was its more rigid mandible (lower jaw). While many theropods, including North American tyrannosaurids, had some degree of flexibility between the bones in the rear of the mandible and the dentary in the front, Tarbosaurus had a locking mechanism formed from a ridge on the surface of the angular, which articulated with a square process on the rear of the dentary.
Some scientists have hypothesized
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
that the more rigid skull of Tarbosaurus was an adaptation to hunting the massive titanosaurid sauropods found in the Nemegt Formation, which did not exist in most of North America during the Late Cretaceous. The differences in skull mechanics also have an impact on tyrannosaurid phylogeny. Tarbosaurus-like articulations between the skull bones are also seen in Alioramus from Mongolia, suggesting that it, and not Tyrannosaurus, is the closest relative of Tarbosaurus. Similarities between Tarbosaurus and Tyrannosaurus might therefore be related to their large size, independently developed through convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
.
Brain structure
A Tarbosaurus skull found in 1948 by Soviet and Mongolian scientists (PIN 553-1, originally called Gorgosaurus lancinator) included the skull cavity that held the brain. Making a plaster castCasting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
, called an endocast, of the inside of this cavity allowed Maleev to make preliminary observations about the shape of a Tarbosaurus brain. A newer polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
rubber cast allowed a more detailed study of Tarbosaurus brain structure and function.
Tyrannosaurus rex brain structure has also been analyzed, and Tarbosaurus was similar, differing only in the positions of some cranial nerve roots, including the trigeminal
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
and accessory nerve
Accessory nerve
In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve...
s. Tyrannosaurid brains were more similar to those of crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns and other reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s than to bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. The total brain volume for a 12 meter (40 ft) Tarbosaurus is estimated at only 184 cubic centimeters (11.2 cu in). The large size of the olfactory bulb
Olfactory bulb
The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...
s, as well as the terminal and olfactory nerve
Olfactory nerve
The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:...
s, suggest that Tarbosaurus had a keen sense of smell, as was also the case with Tyrannosaurus. The vomeronasal bulb is large and differentiated from the olfactory bulb, indicating a well-developed Jacobsen's organ, which was used to detect pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s. This may imply that Tarbosaurus had complex mating behavior. The auditory nerve was also large, suggesting good hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
, which may have been useful for auditory communication
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...
and spatial awareness. The nerve had a well-developed vestibular
Vestibular system
The vestibular system, which contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of...
component as well, which implies a good sense of balance and coordination. In contrast, the nerves and brain structures associated with eyesight were smaller and undeveloped. The midbrain tectum
Midbrain tectum
The tectum is a region of the brain, specifically the dorsal part of the mesencephalon . This is contrasted with the tegmentum, which refers to the region ventral to the ventricular system...
, responsible for visual processing in reptiles, was very small in Tarbosaurus, as were the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
and the oculomotor nerve
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
, which controls eye movement. Unlike Tyrannosaurus, which had forward-facing eyes that provided some degree of binocular vision, Tarbosaurus had a narrower skull more typical of other tyrannosaurids in which the eyes faced primarily sideways. All of this suggests that Tarbosaurus relied more on its senses of smell and hearing than on its eyesight.
Paleopathology
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by regular behavior than other types of injuries. None of the 18 Tarbosaurus foot bones examined in the study was found to have a stress fracture, but one of the 10 examined hand bones was found to have one. Stress fractures in the hands have special behavioral significance compared to those found in the feet since stress fractures there can be obtained while running or during migration. Hand injuries, by contrast, are more likely to be obtained while in contact with struggling prey. The presence of stress fractures and tendon avulsions in general provide evidence for a "very active" predation-based diet rather than obligate scavenging.Paleoecology
Nemegt Formation
The Nemegt Formation is a geological formation dating from the Late Cretaceous sedimentary from the Gobi Desert of Mongolia. It overlies and sometimes forms folds with the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a...
in the Gobi Desert
Gobi Desert
The Gobi is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia. The desert basins of the Gobi are bounded by the Altai Mountains and the grasslands and steppes of Mongolia on the north, by the Hexi Corridor and Tibetan Plateau to the...
of southern Mongolia. This geologic formation
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
has never been dated radiometrically
Radiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
, but the fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
present in the fossil record indicate it was probably deposited during the early Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage, at the end of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
about 70 million years ago. The Subashi Formation
Subashi Formation
The Subashi Formation is a late Cretaceous formation from the Xinjiang Autonomous Region of western China. Initially described by Dong Zhiming in 1977, the formation contains remains of Tarbosaurus which were initially described as a separate taxon Shanshanosaurus huoyanshanensis...
, in which Shanshanosaurus remains were discovered, is also Maastrichtian in age.
Nemegt sediments preserve large river channels and soil deposits that indicate a far more humid climate than those suggested by the underlying Barun Goyot
Barun Goyot Formation
The Barun Goyot Formation , dating from the Late Cretaceous Period, is located within and is widely represented in the Gobi Desert basin, in the Ömnögovi Province of Mongolia....
and Djadochta Formation
Djadochta Formation
The Djadochta Formation is situated in central Asia 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...
s. However, caliche
Caliche (Mineral)
Caliche is a sedimentary rock, a hardened deposit of calcium carbonate. This calcium carbonate cements together other materials, including gravel, sand, clay, and silt. It is found in aridisol and mollisol soil orders...
deposits indicate at least periodic droughts. Sediment was deposited in the channels and floodplains of large rivers. Occasional mollusc fossils are found, as well as a variety of other aquatic animals like fish and turtles. Crocodilians included several species of Shamosuchus
Shamosuchus
Shamosuchus is an extinct genus of neosuchian crocodile that lived during the Late Cretaceous period in what is now the Gobi desert of Mongolia, approximately 85 to 65 million years ago. The teeth were adapted to crush bivalves, gastropods and other animals with a shell or exoskeleton . The genus...
, a genus with teeth adapted for crushing shells. Mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
fossils are exceedingly rare in the Nemegt Formation, but many birds have been found, including the enantiornithine Gurilynia
Gurilynia
Gurilynia was a Genus of enantiornithine birds. One species is known, G. nessovi. It lived during the Maastrichtian stage of the Late Cretaceous period, between 70 and 65 mya. Gurilynia is known from fragmentary fossils found at the Gurilyn Tsav locality of the Nemegt Formation in south Gobi,...
and the hesperornithiform
Hesperornithes
Hesperornithes is an extinct and highly specialized clade of Cretaceous toothed birds. Hesperornithine birds, apparently limited to former aquatic habitats in the Northern Hemisphere, include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and probably Potamornis, all...
Judinornis
Judinornis
Judinornis is a prehistoric flightless bird genus from the Late Cretaceous. The single known species is Judinornis nogontsavensis...
, as well as Teviornis
Teviornis
Teviornis is a genus of extinct birds. One species has been described, T. gobiensis. It lived in the Maastrichtian stage at the end of the Late Cretaceous period, some 70 million years ago. It is known from fossils collected from the Nemegt Formation of Gobi, south Mongolia.The fossils include only...
, an early representative of the still-existing Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
(waterfowl), a bird order. Scientists have described many dinosaurs from the Nemegt Formation, including ankylosaurids such as Tarchia
Tarchia
Tarchia is a genus of ankylosaurid dinosaur from the late Cretaceous of Mongolia. It is currently the geologically youngest known of all the Asian ankylosaurid dinosaurs and is represented by five or more specimens, including two complete skulls and one nearly complete postcranial skeleton...
, and pachycephalosaurs such as Homalocephale
Homalocephale
Homalocephale is a genus of dinosaur belonging to the pachycephalosaurid family, which lived during the late Cretaceous period of what is now Mongolia, 80 million years ago. The genus was described in 1974 by Osmólska & Maryañska, and consists of a single species, H...
and Prenocephale
Prenocephale
Prenocephale was a small pachycephalosaurid dinosaur genus from the Late Cretaceous and was similar in many ways to its close relative, Homalocephale, which may simply represent Prenocephale juveniles. Adult Prenocephale probably weighed around and measured around long...
. By far the largest predator known from the formation, adult Tarbosaurus most likely preyed upon large hadrosaurs such as Saurolophus
Saurolophus
Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 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...
and Barsboldia
Barsboldia
Barsboldia was a genus of large hadrosaurid dinosaur from the early Maastrichtian Nemegt Formation of Ömnogöv', Mongolia. It is known from a partial vertebral column, partial pelvis, and some ribs...
, or sauropods such as Nemegtosaurus, and Opisthocoelicaudia
Opisthocoelicaudia
Opisthocoelicaudia was 12-metre-long sauropod dinosaur of the Late Cretaceous Period discovered in Mongolia in 1965 by Polish and Mongolian scientists in what is now the Gobi Desert...
. Adults would have received little competition from small theropods such as troodontids (Borogovia
Borogovia
Borogovia was a theropod dinosaur genus which lived during the Late Cretaceous Period, in what is now Mongolia. The agile carnivorous troodontid takes its name from creatures known as 'borogoves' in the Lewis Carroll poem, Jabberwocky....
, Tochisaurus
Tochisaurus
Tochisaurus is a genus of small theropod dinosaur. It lived during the Late Cretaceous Period. Its fossils, consisting solely of the metatarsus, were found in Mongolia. The type species is T. nemegtensis, formalized by Kurzanov and Osmólska in 1991...
, Saurornithoides
Saurornithoides
Saurornithoides is a genus of troodontid maniraptoran dinosaur, living during the Late Cretaceous period. These creatures were predators, which could run fast on their hind legs and had excellent sight and hearing...
), oviraptorosaurs (Elmisaurus
Elmisaurus
Elmisaurus is an extinct genus of dinosaur from the Late Cretaceous. It was a theropod belonging to the Oviraptorosauria. Its fossils have been found in Asia and North America. It is known from only its feet and hands....
, Nemegtomaia
Nemegtomaia
Nemegtomaia is a genus of oviraptorid dinosaur from the late Cretaceous Period of what is now Mongolia. The type species, Nemegtomaia barsboldi, was described by Lü, Tomida, Azuma, Dong, and Lee in 2004...
, Rinchenia
Rinchenia
Rinchenia is a genus of Mongolian oviraptorid dinosaur from the late Cretaceous Period. The type species, Rinchenia mongoliensis, was originally classified as a species within the genus Oviraptor , but a re-examination by Barsbold in 1997 found differences significant enough to warrant a separate...
) or Bagaraatan
Bagaraatan
Bagaraatan was 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 3–4 metres in length....
, sometimes considered a basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
tyrannosauroid. Other theropods, like the gigantic Therizinosaurus
Therizinosaurus
Therizinosaurus is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period , and was one of the last and largest representatives of its unique group, the Therizinosauria...
, may have been herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, and ornithomimosaurs such as Anserimimus
Anserimimus
Anserimimus is a genus of ornithomimid theropod dinosaur, from the Late Cretaceous Period of what is now Mongolia. It was a lanky, fast-running animal, possibly an omnivore...
, Gallimimus
Gallimimus
Gallimimus is a genus of ornithomimid theropod dinosaur from the late Cretaceous period Nemegt Formation of Mongolia. With individuals as long as , it was one of the largest ornithomimosaurs...
, and Deinocheirus
Deinocheirus
Deinocheirus is a genus of large theropod dinosaur, possibly an ornithomimosaurian, which lived in what is now southern Mongolia, during the late Cretaceous Period .-Discovery and naming:...
might have been omnivores that only took small prey and were therefore no competition for Tarbosaurus. However, as in other large tyrannosaurids as well as modern Komodo dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...
s, juveniles and subadult Tarbosaurus may have filled niches between the massive adults and these smaller theropods.
External links
Images and photos.- Skeletal image of Shanshanosaurus at The Grave Yard.
- Comparison between Tarbosaurus skulls from specimens of different age group and size.
Readable material.
- Discussion and specimen list at The Theropod Database.
- Review of the Tyrannosauridae by George OlshevskyGeorge OlshevskyGeorge Olshevsky is a freelance editor, writer, publisher, amateur paleontologist, and mathematician living in San Diego, California.Olshevsky maintains the comprehensive online Dinosaur Genera List...
(1995). - Scienceblogs: Juvenile, 5 years old Tarbosaurus specimen found in Mongolia 2006.