''Tarbosaurus'' ( ; meaning "alarming lizard") is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
tyrannosaurid
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
that flourished in
Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
about 70
million years ago
The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds.
Usage
Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...
, at the end of the Late
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
Period, considered to contain a single known species, ''Tarbosaurus bataar''.
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s have been recovered from the
Nemegt Formation of
Mongolia
Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...
, with more fragmentary remains found further afield in the
Subashi Formation of
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
.
Although many
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
have been named, modern paleontologists recognize only one, ''T. bataar'', as valid. Some experts see this species as an Asian representative of the
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
n genus ''
Tyrannosaurus
''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...
''; this would make the genus ''Tarbosaurus'' redundant. ''Tarbosaurus'' and ''Tyrannosaurus'', if not
synonymous
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
, are considered to be at least closely related genera. ''
Alioramus'', also from Mongolia, has previously been thought by some authorities to be the closest relative of ''Tarbosaurus'', though this has since been disproven with the discovery of ''
Qianzhousaurus
''Qianzhousaurus'' (meaning "Qianzhou lizard") is a genus of tyrannosaurid dinosaurs that lived in Asia during the Late Cretaceous period. There is currently only one species named, the type species ''Qianzhousaurus sinensis'' which is a member ...
'' and the description of the Alioramini.
Like most known tyrannosaurids, ''Tarbosaurus'' was a large
bipedal
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
, measuring approximately in length, in hip height and weighing up to in body mass. It had a unique locking mechanism in its jaw, equipped with about sixty large teeth, 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
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
criss-crossed by river channels. In this environment, it was an
apex predator, probably preying on other large dinosaurs like the
hadrosaur
Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includ ...
''
Saurolophus
''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 68 million ...
'' or the
sauropod
Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...
''
Nemegtosaurus''. ''Tarbosaurus'' is represented by dozens of
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its
phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...
, skull mechanics, and brain structure.
Discovery and naming
![Tarbosaurus holotype skull](https://upload.wikimedia.org/wikipedia/commons/4/47/Tarbosaurus_holotype_skull.jpg)
In 1946, a joint
Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
-Mongolian expedition to the
Gobi Desert
The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world.
Geography
The Gobi measures from southwest to northeast an ...
in the Mongolian
Ömnögovi Province turned up a large theropod skull and some
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
e in the
Nemegt Formation. In 1955,
Evgeny Maleev
Evgeny Aleksandrovich Maleev (, ; 25 February 1915 – 12 April 1966) was a Soviet and Russian paleontologist who did most of his research on reptiles and Asian fossils, such as the naming of the ankylosaur ''Talarurus'' and theropods ''Tarbo ...
, a Soviet
paleontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
, made this specimen the
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
(
PIN
A pin is a device used for fastening objects or material together.
Pin or PIN may also refer to:
Computers and technology
* Personal identification number (PIN), to access a secured system
** PIN pad, a PIN entry device
* PIN, a former Dutch de ...
551–1) of a new species, which he called ''Tyrannosaurus bataar''.
[ The specific 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 includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
''τάρβος'' (') ("terror", "alarm", "awe", or "reverence") and (') ("lizard"), and the species named after Ivan Yefremov, a Russian paleontologist and science fiction
Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...
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
''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosa ...
''. 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
''Chinggis Khaan'' ͡ʃʰiŋɡɪs xaːŋbr />Mongol script: ''Chinggis Qa(gh)an/ Chinggis Khagan''
, birth_name = Temüjin
, successor = Tolui (as regent)Ögedei Khan
, spouse =
, issue =
, house = Borjigin
, ...
) 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
Polish may refer to:
* Anything from or related to Poland, a country in Europe
* Polish language
* Poles, people from Poland or of Polish descent
* Polish chicken
*Polish brothers (Mark Polish and Michael Polish, born 1970), American twin screenwr ...
-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 ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
ese and Mongolian scientists between 1993 and 1998, as well as private expeditions hosted by Canadian
Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...
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.[
]
Poached specimens
''Tarbosaurus'' fossils are only found around the Gobi Desert of Mongolia and China, both of which ban their export, though some specimens have been looted by private collectors. A $1 million smuggling deal was uncovered when suspicions were raised about a catalog put out by Heritage Auctions for an event in New York City on May 20, 2012. By Mongolian law, any specimen found in the Gobi Desert
The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world.
Geography
The Gobi measures from southwest to northeast an ...
was to rest at an appropriate Mongolian institution and there was little reasonable doubt that the ''Tarbosaurus bataar'' advertised on the catalog was a stolen one. The president of Mongolia and many paleontologists raised objections to the sale which led to a last-minute investigation that confirmed that it was a specimen that can only be found in the Gobi Desert, rightfully belonging to Mongolia. During the court case ( United States v. One ''Tyrannosaurus Bataar'' Skeleton), Eric Prokopi, the smuggler, pleaded guilty to illegal smuggling and the dinosaur was returned to Mongolia in 2013, where it is temporarily displayed on Sukhbaatar Square, the center of the city of Ulaanbaatar. Prokopi had sold the dinosaur with a partner and fellow commercial hunter in England, Christopher Moore. The case led to the repatriation of dozens more Mongolian dinosaurs, including several skeletons of ''Tarbosaurus bataar''.
Synonyms
Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of va ...
paleontologists discovered a partial skull and skeleton of a small theropod (IVPP The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name suggest ...
V4878) in the Xinjiang
Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...
Autonomous Region of China in the mid-1960s. In 1977, Dong Zhiming described this specimen, which was recovered from the Subashi Formation in Shanshan County
Shanshan County () as the official romanized name, also transliterated from Uyghur as Piqan County (; ), is a county within the Xinjiang Uyghur Autonomous Region and is under the administrative jurisdiction of the prefecture-level city of Turpan ...
, 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 tyrannosaurine. These authors refrained from assigning it to any particular genus but suggested ''Tarbosaurus'' as a possibility.
''Albertosaurus periculosus'', ''Tyrannosaurus luanchuanensis'', ''Tyrannosaurus turpanensis'' and '' Chingkankousaurus fragilis'' were considered synonyms of ''Tarbosaurus'' in the second edition of the Dinosauria, but ''Chingkankousaurus'' has been assessed as dubious by Brusatte et al. (2013).[
Named in 1976 by ]Sergei Kurzanov
Sergei Mikhailovich Kurzanov (Сергей Михайлович Курзанов, born 1947) is a Russian (formerly Soviet) paleontologist at the Paleontological Institute of the Russian Academy of Sciences. He is known mainly for his work in Mongo ...
, '' 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.][
]
Skin impressions and footprints
Skin impressions were recovered from a large skeleton at the Bugiin Tsav locality that was subsequently destroyed by poachers. These impressions show non-overlapping scales with an average diameter of and pertain to the thoracic region of the individual, although the exact position can not be assessed any longer due to the destruction of the skeleton.
Phil Currie and colleagues (2003) described two footprints from the Nemegt locality that probably pertain to ''Tarbosaurus''. These tracks represent natural casts, which means that only the sandy infill of the tracks and not the tracks themselves are preserved. The better-preserved track features skin impressions over large areas on and behind the toe impressions that are similar to those discovered in Bugiin Tsav; it also features vertical parallel slide marks that were left by scales when the foot was pushed into the ground. The track measures in length, thus representing a large individual. The second track, although even larger, was affected by erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
and does not show any detail.
In 1997, Kenneth Carpenter reported a damaged ''Tarbosaurus'' skull with impressions of a dewlap or throat pouch beneath the lower jaws, based on a personal communication from Konstantin Mikhailov. Carpenter speculated that the pouch may have been used for display, possibly being brightly colored and inflatable like a frigatebird's. In a 2019 communication to Mickey Mortimer, Mikhailov confirmed that this specimen had not been collected due to its being on a heavy stone slab. He revealed that it had been discovered by Sergei Kurzanov
Sergei Mikhailovich Kurzanov (Сергей Михайлович Курзанов, born 1947) is a Russian (formerly Soviet) paleontologist at the Paleontological Institute of the Russian Academy of Sciences. He is known mainly for his work in Mongo ...
and that it was Kurzanov who had originally interpreted the impressions as a throat structure. This specimen may be the same as one that was purportedly destroyed by poachers in 1992.
Description
Although slightly smaller than ''Tyrannosaurus'', ''Tarbosaurus'' was one of the largest tyrannosaurids, with the largest fully grown individual measuring approximately in length, in hip height and weighing up to in body mass (based on tibia and femur circumference and volumetric analysis). The largest known ''Tarbosaurus'' skull is more than long, larger than all other tyrannosaurids except ''Tyrannosaurus''.
Skull
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 58 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
Cross section may refer to:
* Cross section (geometry)
** Cross-sectional views in architecture & engineering 3D
*Cross section (geology)
* Cross section (electronics)
* Radar cross section, measure of detectability
* Cross section (physics)
**Abs ...
, although the teeth of the premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
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
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
(upper jaw bone), with crowns
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
up to 85 millimeters (3.3 in) long. In the lower jaw, a ridge on the outer surface of the angular bone The angular is a large bone in the lower jaw (mandible) of amphibians and reptiles (birds included), which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the art ...
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.
Postcranial skeleton
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
The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
, 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,[Carpenter K, Tanke D.H. & Skrepnick M.W. (2001), ''Mesozoic Vertebrate Life'' (]Indiana University Press
Indiana University Press, also known as IU Press, is an academic publisher founded in 1950 at Indiana University that specializes in the humanities and social sciences. Its headquarters are located in Bloomington, Indiana. IU Press publishes 140 ...
, ), p. 71. 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
''Daspletosaurus'' ( ; meaning "frightful lizard") is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 79.5 and 74 million years ago, during the Late Cretaceous Period. The genus ''Daspletosaurus'' contains three species ...
''), the third metacarpal is often longer than the first metacarpal, while in the ''Tarbosaurus'' specimens studied by Holtz, 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
A counterweight is a weight that, by applying an opposite force, provides balance and stability of a mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves energy and causes less wear ...
to the head and torso and placed the center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
over the hips.
Classification
''Tarbosaurus'' is classified as a theropod in the subfamily Tyrannosaurinae within the family Tyrannosauridae. Other members include ''Tyrannosaurus'' and the earlier ''Daspletosaurus
''Daspletosaurus'' ( ; meaning "frightful lizard") is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 79.5 and 74 million years ago, during the Late Cretaceous Period. The genus ''Daspletosaurus'' contains three species ...
'', 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
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
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 some 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 argue against ''Tarbosaurus'' becoming a synonym for ''Tyrannosaurus'' and would suggest that separate tyrannosaurine lineages ]evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
in Asia and North America.[ The two known specimens of ''Alioramus'', which show juvenile characteristics, are not likely juvenile individuals of ''Tarbosaurus'' because of their much higher tooth count (76 to 78 teeth) and their unique row of bony bumps along the top of their snouts.]
The discovery of ''Lythronax argestes
''Lythronax'' () is a genus of tyrannosaurid dinosaur that lived in North America around 81.9-81.5 million years ago during the Late Cretaceous period. The only known specimen was discovered in Utah in the Wahweap Formation of the Grand Stairca ...
'', a much earlier tyrannosaurine further reveals the close relationship between ''Tyrannosaurus'' and ''Tarbosaurus'', and it was discovered that ''Lythronax'' is a sister taxon to a clade consisting of Campanian genus ''Zhuchengtyrannus'', and Maastrichtian genera ''Tyrannosaurus'' and ''Tarbosaurus''. Further studies of ''Lythronax'' also suggest that the Asian tyrannosauroids were part of one evolutionary radiation.
Below is the cladogram of Tyrannosaurinae based on the phylogenetic analysis conducted by Voris and team in 2020.
Paleobiology
Ontogeny
Most specimens of ''Tarbosaurus'' represent adult or subadult individuals; juveniles remain very rare. Nevertheless, the 2006 discovery of a juvenile individual (MPC-D 107/7) including a complete, long skull was reported and described in 2011 and provides information on the life history of this dinosaur. This individual probably was aged 2 to 3 years at the time of death. Compared with adult skulls, the juvenile skull was weakly constructed and the teeth were thin, indicating different food preferences in juveniles and adults that reduced competition between different age groups. Examination of the sclerotic rings in this juvenile ''Tarbosaurus'' suggests they may also have been crepuscular or nocturnal hunters. Whether the adult ''Tarbosaurus'' were also nocturnal is currently unknown due to lack of fossil evidence.
Senses
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 cast
Cast may refer to:
Music
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* ''Cast'', a 2012 album by Trespassers William
* ...
, 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.
The endocranial structure of ''Tarbosaurus'' was similar to that of ''Tyrannosaurus'', differing only in the positions of some cranial nerve
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and ...
roots, including the trigeminal
In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewing ...
and accessory nerve
The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerv ...
s. Tyrannosaurid brains were more similar to those of crocodilia
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...
ns and other nonavian reptiles than to bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s. The total brain volume for a ''Tarbosaurus'' is estimated at only .[
The large size of the ]olfactory bulb
The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...
s, as well as the terminal
Terminal may refer to:
Computing Hardware
* Terminal (electronics), a device for joining electrical circuits together
* Terminal (telecommunication), a device communicating over a line
* Computer terminal, a set of primary input and output devic ...
and olfactory nerve
The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell.
The afferent nerve fibers of the olfactory receptor neurons tr ...
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, which was initially suggested as being indicative of a well-developed Jacobsen's organ, which was used to detect pheromones. This may imply that ''Tarbosaurus'' had complex mating behavior.[ However, the identification of the vomeronasal bulb has been challenged by other researchers, since they are not present in any living archosaurs.]
The auditory nerve
The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information ...
was also large, suggesting good hearing, which may have been useful for auditory communication
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
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
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', "m ...
, responsible for visual processing in reptiles, was very small in ''Tarbosaurus'', as were the optic nerve
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...
and the oculomotor nerve
The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...
, 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.[ It has been suggested that the lack of binocular vision in Asian tyrannosaurs like ''Tarbosaurus'' might have been correlated with a greater amount of scavenging resources provided by sauropod carcasses, which might have afforded them a less active predatory lifestyle compared to the North American forms, and thus less predatory adaptations.
]
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, force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
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
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 by their junction, form the bridge of the upper one third of the nose.
Eac ...
s on top of the snout, which were firmly connected in the rear to the lacrimal bones 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
Front may refer to:
Arts, entertainment, and media Films
* ''The Front'' (1943 film), a 1943 Soviet drama film
* ''The Front'', 1976 film
Music
*The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
and 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 ...
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
A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obser ...
that the more rigid skull of ''Tarbosaurus'' was an adaptation to hunting the massive titanosaurid
Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of '' Malawisaurus'' and '' Saltasaurus'' ...
sauropod
Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...
s found in the Nemegt Formation, which did not exist in most of North America during the Late Cretaceous. The differences in skull mechanics also affect 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 is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.[
]
Bite force and feeding
In 2001, Bruce Rothschild
The English language name Bruce arrived in Scotland with the Normans, from the place name Brix, Manche in Normandy, France, meaning "the willowlands". Initially promulgated via the descendants of king Robert the Bruce (1274−1329), it has been a ...
and others published a study examining evidence for stress fractures and tendon avulsions
An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament by the application of forces external to the body (such as a fa ...
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 eighteen ''Tarbosaurus'' foot bones examined in the study was found to have a stress fracture, but one of the ten 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.[Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.]
As for its bite force, it was revealed in 2005 that ''Tarbosaurus'' had a bite force of around 8,000 to 10,000 pounds per force, meaning that it could possibly crush bone like its North American relative, ''Tyrannosaurus''.
David W.E. Hone and Mahito Watabe in 2011 reported the left humerus of a nearly complete ''Saurolophus
''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 68 million ...
'' skeleton (MPC-D 100/764) from the Bügiin Tsav locality of the Nemegt Formation, which was heavily damaged from bite marks attributed to ''Tarbosaurus''. As suggested by the lack of damage to the rest of the skeleton (such as large wounds in skeletal remains indicative of predation
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
), this tyrannosaurid was likely scavenging an already dead ''Saurolophus''. It is unlikely that a large-bodied predator such as ''Tarbosaurus'' would have left sparse feeding traces on a single humerus having an entire carcass to feed on. The humerus shows three distinctive feeding methods, interpreted as punctures, drag marks, and bite−and−drag marks. Hone and Watabe noted that bite marks were mostly located at the deltopectoral crest, suggesting that this ''Tarbosaurus'' was actively selecting which biting style employ to scavenge the bone.
In 2012, bite marks on two fragmentary gastralia of the holotype specimen of the large ornithomimosaur ''Deinocheirus mirificus
''Deinocheirus'' ( ) is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Ne ...
'' were reported. The size and shape of the bite marks match the teeth of ''Tarbosaurus'', the largest known predator from the Nemegt Formation. Various types of feeding traces were identified; punctures, gouges, striae, fragmentary teeth, and combinations of the above marks. The bite marks probably represent feeding behavior instead of aggression between the species, and the fact that bite marks were not found elsewhere on the body indicates the predator focused on internal organs. ''Tarbosaurus'' bite marks have also been identified on hadrosaur and sauropod fossils, but theropod bite marks on bones of other theropods are very rare in the fossil record.
A 2020 study involving stable isotopes found that ''Tarbosaurus'' primarily hunted large dinosaurs in its environment, most notably titanosaurs and hadrosaurs.
Paleoenvironment
The vast majority of known ''Tarbosaurus'' fossils were recovered from the Nemegt Formation in the Gobi Desert
The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world.
Geography
The Gobi measures from southwest to northeast an ...
of southern Mongolia. This geologic formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
has never been dated radiometrically, but the fauna
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zoo ...
present in the fossil record indicate it was probably deposited during the early Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...
stage, at the near end of the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
about 70 million years ago.[Sulliban, R.M. (2006). "A taxonomic review of the Pachycephalosauridae (Dinosauria: Ornithischia)." Pp. 347-366 in Lucas, S.G. and Sullivan, R.M. (eds.), ''Late Cretaceous vertebrates from the Western Interior.'' New Mexico Museum of Natural History and Science Bulletin 3.] The Subashi Formation, in which ''Shanshanosaurus'' remains were discovered, is also Maastrichtian in age.
''Tarbosaurus'' is found chiefly in the Nemegt Formation, whose sediments preserve large river channels and soil deposits that indicate a far more humid climate than those suggested by the underlying Barun Goyot
The Barun Goyot Formation (also known as Baruungoyot Formation or West 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 Prov ...
and Djadochta Formation
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 milli ...
s. However, caliche deposits indicate at least periodic droughts. Sediment was deposited in the channels and floodplains of large rivers. The rock facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...
of this formation suggest the presence of mudflats, and shallow lakes. Sediments also indicate that there existed a rich habitat, offering diverse food in abundant amounts that could sustain massive Cretaceous dinosaurs.[Novacek, M. (1996). Dinosaurs of the Flaming Cliffs. Bantam Doubleday Dell Publishing Group Inc. New York, New York. ] Fossils of an unidentified tyrannosaur from the older Djadochta Formation, which closely resemble those of ''Tarbosaurus'', may indicate that it also lived at an earlier time and in a more arid ecosystem than that of the Nemegt.
Occasional mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...
fossils are found, as well as a variety of other aquatic animals like fish and turtles.[ Crocodilians included several species of '' Paralligator'', a genus with teeth adapted for crushing shells.] Mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
fossils are exceedingly rare in the Nemegt Formation, but many birds have been found, including the enantiornithine
The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...
''Gurilynia
''Gurilynia'' is a genus of enantiornithine birds.Kurochkin, E.N. (1999) "A new large enantiornithid from the Late Cretaceous of Mongolia." In I. Darevskii and A. Averianov (editors), "Materials on the History of Fauna of Eurasia. Zoological Ins ...
'' and the hesperornithiform
Hesperornithes is an extinct and highly specialized group of aquatic avialans closely related to the ancestors of modern birds. They inhabited both marine and freshwater habitats in the Northern Hemisphere, and include genera such as ''Hesperorni ...
''Judinornis
''Judinornis'' is a genus of prehistoric flightless birds from the late Cretaceous period. The single known species is ''Judinornis nogontsavensis''. Its fossils have been found in Nemegt Formation rocks of southern Mongolia, and though the age ...
'', as well as '' Teviornis'', an early representative of the still-existing Anseriformes
Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which in ...
(waterfowl). Scientists have described many dinosaurs from the Nemegt Formation, including the ankylosaurid '' Saichania'', and pachycephalosaur
Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachyc ...
'' Prenocephale''.[ By far the largest predator known from the formation, adult ''Tarbosaurus'' most likely preyed upon large hadrosaurs such as '']Saurolophus
''Saurolophus'' (; meaning "lizard crest") is a genus of large hadrosaurid dinosaur from the Late Cretaceous period of Asia and North America, that lived in what is now the Horseshoe Canyon and Nemegt formations about 70 million to 68 million ...
'' and ''Barsboldia
''Barsboldia'' (meaning "of Barsbold", a well-known Mongolian paleontologist) is a genus of large hadrosaurid dinosaur from the early Maastrichtian Nemegt Formation of Ömnogöv', Mongolia. It is known from a partial vertebral column, parti ...
'', or sauropods such as '' Nemegtosaurus'', and '' Opisthocoelicaudia''.[ Adults would have received little competition from small theropods such as the small ]tyrannosaurid
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...
'' Alioramus'', troodontids (''Borogovia
''Borogovia'' is a troodontid theropod dinosaur genus which lived during the Late Cretaceous Period, in what is now Mongolia.
In 1971, a Polish-Mongolian expedition discovered the remains of a small theropod at the Altan Ula IV site, in the N ...
'', ''Tochisaurus
''Tochisaurus'' (meaning "Ostrich lizard") is a genus of small troodontid theropod dinosaur from the Late Cretaceous Period of Mongolia. The type (and only named) species is ''Tochisaurus nemegtensis''.
In 1948, a Soviet-Mongolian expedition fo ...
'', ''Zanabazar
Öndör Gegeen Zanabazar, , , "High Saint Zanabazar"; 1635–1723 (born Eshidorji) was the sixteenth '' Jebtsundamba Khutuktu'' and the first ''Bogd Gegeen'' or supreme spiritual authority, of the Gelugpa (Yellow Hat) lineage of Tibetan Buddhism ...
''), oviraptorosaurs ('' Elmisaurus'', '' Nemegtomaia'', '' Rinchenia'') or '' Bagaraatan'', sometimes considered a basal tyrannosauroid
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 b ...
. Other theropods, like the gigantic ''Therizinosaurus
''Therizinosaurus'' (; meaning 'scythe lizard') is a genus of very large therizinosaurid that lived in Asia during the Late Cretaceous period in what is now the Nemegt Formation around 70 million years ago. It contains a single species, ''Therizi ...
'', might have been herbivorous, and ornithomimosaurs such as ''Anserimimus
''Anserimimus'' ( ; "goose mimic") 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. From what fossils are known, it probably closely ...
'', ''Gallimimus
''Gallimimus'' ( ) is a genus of theropod dinosaur that lived in what is now Mongolia during the Late Cretaceous period, about seventy million years ago (mya). Several fossils in various stages of growth were discovered by Polish-Mongolian exped ...
'', and gigantic ''Deinocheirus
''Deinocheirus'' ( ) is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Ne ...
'' 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
The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a member of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo, Rinca, Flores, and Gili Motang. It is the largest extant ...
s, juveniles and subadult ''Tarbosaurus'' would have filled niches between the massive adults and these smaller theropods.[
]
See also
* 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 Theropoda, theropod dinosaurs that began as small, long-armed bird-like creatures with ela ...
References
External links
Images and photos
Skeletal image
of ''Shanshanosaurus'' a
Comparison between ''Tarbosaurus'' skulls from specimens of different age group and size
Readable material
at The Theropod Database.
by George Olshevsky (1995).
* ''Scienceblogs:'
Juvenile, 5 years old ''Tarbosaurus'' specimen found in Mongolia 2006
{{Taxonbar, from=Q2491
Tyrannosaurids
Monotypic dinosaur genera
Maastrichtian life
Late Cretaceous dinosaurs of Asia
Apex predators
Cretaceous Mongolia
Fossils of Mongolia
Nemegt fauna
Fossil taxa described in 1955
Taxa named by Evgeny Maleev