Tarbosaurus

TarbosaurusAlarming Lizard
Classification
Domain	Eukaryota
Kingdom	Animalia
Phylum	Chordata
Subphylum	Vertebrata
Superclass	Tetrapoda
Clade	Sauropsida
Class	Reptilia
Clade	Archosauria Avemetatarsalia Ornithodira Dinosauria Saurischia Theropoda Neotheropoda Averostra Tetanurae Orionides Avetheropoda Coelurosauria
Superfamily	Tyrannosauroidea
Family	Tyrannosauridae
Subfamily	Tyrannosaurinae
Tribe	Tyrannosaurini
Species	Tarbosaurus bataar
Presence
Location	Nemegt Formation, Ömnögovi Province, northwest Gobi Desert, south Mongolia (T. bataar) Subashi Formation, Xinjiang Autonomous Region, west China ("Shanshanosaurus") Djadochta Formation, Ömnögovi Province, northwest Gobi Desert, south Mongolia (Indeterminate tyrannosaur remains)
Temporal Range	70 million years ago, Maastrichtian Stage, Late Cretaceous Period (possibly around since 75 million years ago, Campanian Stage)
Episodes	Deserts (Segments 2 and 4) Badlands (Segment 2) How Did Dinosaurs Get So Big? (Cameo)
Characteristics
Height	3.5 meters (11 feet, 6 inches)
Length	10 - 12 meters (33 - 40 feet)
Mass	4.5 - 7 metric tons (5 - 7.7 short tons)
Diet	Carnivorous
Skull Length of 1.3 - 1.6 meters (4 feet, 4 inches - 5 feet, 3 inches) Brain Volume of 184 cubic centimeters (11.23 cubic inches) Anterior (Front) Bite Force of 13,300 newtons, or 1.36 metric tons (1.5 short tons) Posterior (Back) Bite Force of 24,253 newtons, or 2.5 metric tons (2.76 short tons) Tooth Count of 58 - 64 Tooth Length of 8.5 centimeters (2 feet, 10 inches) (crown only) Shares a unique jaw-locking mechanism with Alioramus, a relative of Qianzhousaurus Has the smallest arms relative to body size of all tyrannosaurids

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“ Tarbosaurus. The equivalent in this desert of T. rex. They keep everyone else away. ”

― David Attenborough, Deserts

Tarbosaurus (Alarming Lizard) is a genus of tyrannosaurid theropod dinosaur that served as the apex predator of the Nemegt Formation in Mongolia and the Subashi Formation in China, 70 million years ago, during the Maastrichtian stage of the Late Cretaceous Period. Remains of a similar animal, an unidentified tyrannosaur from the Djadochta Formation in Mongolia, if proven to belong to Tarbosaurus, may indicate that it was around even earlier, 75 - 71 million years ago, during the Campanian Stage of the Late Cretaceous Period.

Paleobiology

Size and Physique

Similar to its North American relative Tyrannosaurus rex, Tarbosaurus is a heavily-built apex predator. However, it is not as robust as its more famous cousin, with a different brow shape and overall slimmer head. While it is slightly smaller and lighter, it is still a massive animal, one of the largest tyrannosaurs. The type specimen, PIN 551–1, measures approximately 10 meters (33 feet) long and 4.5 – 5 metric tons (5.0 – 5.5 short tons) in terms of weight, with a skull that is 1.3 meters (4 feet, 4 inches) long. Estimates account for the possibility of a 12-meter (40-foot) Tarbosaurus (which, based on the head-to-body proportions of the holotype specimen, may have had a skull that is 1.6 meters or 5 feet and 3 inches in length), with one study calculating the brain of a Tarbosaurus that size being only around 184 cubic centimeters (11.23 cubic inches) in volume.

Jaws and Dentition

The skull of Tarbosaurus was tall like that of Tyrannosaurus, but not as wide, especially towards the back. Even so, the head, filled with 58 - 64 teeth with crowns that can grow to lengths of 8.5 centimeters (2 feet, 10 inches), was large and powerful enough to crush bone. A study in 2005 suggests that Tarbosaurus exerted a bite force of around 4 - 5 tons (10,000 - 12,000 pounds), while a 2022 study estimates that a Tarbosaurus with a skull width of 616 millimeters (24.3 inches) possesses an anterior (front) bite force of 13,300 newtons or 1.36 metric tons (1.5 short tons), and a posterior (back) bite force of 2,453 newtons or 2.5 metric tons (2.76 short tons). A 2023 study gives an even lower value based on Tarbosaurus specimen ZPAL MGD-l/4, which is estimated to exert approximately 11,905 newtons or 1.21 metric tons (1.33 short tons), though it should be noted that ZPAL MGD-l/4 is slightly smaller than the holotype specimen, PIN 551–1, showing how not all adults reach the same size.

Tarbosaurus is differentiated from its North American relatives by its more rigid upper jaw. When biting the down on prey, North American tyrannosaurs transmitted the resulting stress of their attack from the maxilla (the primary tooth-bearing bone of the upper jaw) to their fused nasal bones, which in turn spread out the stress to the lacrimal bones (which form the eye corners nearest to the snout) via a strong connection of bony struts, which locked the bones together whenever the animal bit down on prey. By contrast, Tarbosaurus lacked the strong connection between the nasal and lacrimal bones. Instead, the maxilla transmitted stress from a bony shelf on its back end, which fits into a sheath formed by the lacrimal bones. The lacrimal bones, in turn, transmitted the stress to the frontal and prefrontal bones they were firmly anchored to. Additionally, while North American tyrannosaurs had a loose connection between the bones at the back of their mandible and their dentary bone (the largest bone of animal mandibles, forming the outer part of the jaw), Tarbosaurus had a ridge on its angular bone (a part of the lower jaw connected to other bones) that allowed it to articulate and lock itself against a square process on the animal's dentary. In summary, this system of ridges, notches, and grooves provide Tarbosaurus with a unique jaw-locking mechanism only shared with Alioramus, a relative of Qianzhousaurus, and it is believed that these features perhaps evolved as an adaptation for dealing with the sauropods that it coexisted with in Mongolia (by contrast, North America only has a single known Late Cretaceous titanosaur, Alamosaurus, which is found in the southernmost lands that T. rex inhabited).

Arms

As with all tyrannosaurs, Tarbosaurus has short arms with two curved claws. In fact, out of all known tyrannosaur species, Tarbosaurus has the smallest arms in proportion to its body size. However, the hands of Tarbosaurus bear stress fractures, damages formed by regular usage and not isolated, one-off events, providing evidence that these arms were not vestigial, having likely gained such stress fractures from contact with struggling prey.

Prehistoric Planet's Portrayal

Main: Tarbosaurus on Prehistoric Planet

Main: Tarbosaurus on Prehistoric Planet

Prehistoric Planet depicts Tarbosaurus with a spotted coat of yellows and browns and sparse, almost unnoticeable feathers. In a sense, its skin pattern shares a very faint resemblance with that of Tyrannosaurus on the show, indicating a connection between the two. As with the other tyrannosaurs featured on Prehistoric Planet, Tarbosaurus bears stripes on its snout (though in its case, they are very faint), and it has been theorized that this is a trait that they all inherited from their last common ancestor. While there is no confirmation of this being the case, Dr. Darren Naish, Prehistoric Planet's lead consultant, shared this fan theory, indicating a degree of support and plausibility for the idea. Even so, the design of Tarbosaurus underwent many revisions and modifications, not only to ensure the accuracy of its appearance, but also to depict the differences between it and T. rex, with every detail about the two closely-related but distinct animals subjected to extensive discussion.

Tarbosaurus also has what seems to be a throat pouch, based on interpretations of skin impressions found in 1997.

Tarbosaurus appears in the second segment of Deserts, where a family of four sleep around a sauropod carcass. When they are accidentally woken up by Velociraptors, the tyrannosaur pack decide to go elsewhere, leaving the carcass to scavengers flying overhead. A lone Tarbosaurus later appears in the fourth segment of Deserts, its intimidating presence disturbing a herd of Barsboldia, which make way for the tyrannosaur as it simply stoops down to drink water from the same oasis they gathered around. A pack of Tarbosauruses are shown living in a maze of canyons in the second segment of Badlands, their presence alone causing a herd of titanosaurs to panic, with one Nemegtosaurus falling off a low ledge and eventually being eaten by the three tyrannosaurs. Stock footage of the Tarbosaurus approaching the temporary oasis in the fourth segment of Deserts is also used in the Uncovered segment "How Did Dinosaurs Get So Big?", with the apex predator of the Nemegt Formation being used as one example of predators growing larger in response to the sauropods in their environment.

Paleoecology

Paleoenvironment

Main: Nemegt Formation

Main: Nemegt Formation

“ Even though some animals are well-adapted to desert conditions, their survival is often on a knife edge, especially here in Asia, where, in the height of summer, temperatures soar above 60 degrees Celsius, and water evaporates in an instant. ”

― David Attenborough, Deserts

The Ömnögovi is the largest aimag (province) of Mongolia, found in the south of the country, in northeast portion of the Gobi Desert. Within this aimag is an area called the Nemegt Basin, known locally as the "Valley of Dragons" due to its rich fossil content. It encompasses three formations showing the states the area underwent throughout the Late Cretaceous, namely, the Djadochta (75 - 71 million years old), Barun Goyot (72 - 71 million years old), and Nemegt (70 million years old) Formations. Tarbosaurus lived in the last of the three formations, which showed evidence of a rich, humid environment with large river channels, tidal flats, and forests. However, the Nemegt Formation is also known to have undergone periodic droughts, and there is precedence for arid regions much like the Gobi Desert today existing in Mongolia during those times, thus justifying the depiction of Tarbosaurus living in or at least traveling through a vast desert environment.

Fragmentary remains of Tarbosaurus (originally described as a distinct genus called Shanshanosaurus) have also been found in the Subashi Formation in western China, an area that probably had conditions similar to those of the Nemegt Formation. Unidentified remains of a similar tyrannosaur which may or may not be Tarbosaurus were also found 75 - 71 million years ago in the Djadochta Formation (which underlies the Barun Goyot and Nemegt Formations), an arid environment of sand dunes with little freshwater save for a few oases, some of which can be temporary, like in the show.

Paleofauna

“ One of the reasons why gigantic carnivores may have reached their large sizes is actually simply because they're trying to keep up. They're trying in an evolutionary arms race to stay in the game, to be able to take on some of these very large herbivores. ”

― Professor Paul Barrett, Natural History Museum

Tarbosaurus is the largest known predator of the Nemegt Formation. Other hunters like velociraptorine dromaeosaurs (e.g. Adasaurus), troodontids (e.g. Borogovia, Tochisaurus, and Zanabazar), and the medium-sized tyrannosaur Alioramus, provide no competition against fully-grown individuals, while less-mature Tarbosaurus took up other lower niches in the area. Tarbosaurus lived alongside large herbivores like Tarchia, Barsboldia, Deinocheirus, Therizinosaurus, and some titanosaurs like Nemegtosaurus, Opisthocoelicaudia, and other, larger titanosaurs that may potentially rival Argentinosaurus in size. While it is not as large as T. rex, it is believed that Tarbosaurus attained its large size in proportion to the other animals in its environment as well as its unique jaw-locking mechanism in order to make it more effective in tackling the massive herbivores it coexisted with.

Tarbosaurus would have also coexisted with smaller creatures like Mononykus, at least eight oviraptorosaurs, Prenocephale, and the medium-sized Gallimimus.

Hunting Tactics and Feeding Preferences

While capable of bringing down prey with its powerful bone-crushing bite, Tarbosaurus is not averse to scavenging to conserve effort, as shown in the second segment of Deserts when a group of Tarbosauruses are shown guarding a rotting sauropod carcass for themselves. True to their name, the mere presence of even one of these "Alarming Lizards" in the area is enough to cause even an entire herd of titanosaurs to panic, a fearsome reputation they use to their advantage.

Social Behavior

“ Tarbosaurs. Asia's version of Tyrannosaurus rex. As the predators approach, panic spreads. ”

― David Attenborough, Badlands

While one Tarbosaurus alone is a force to be reckoned with, as shown in the second and fourth segment of Deserts as well as the second segment of Badlands, Tarbosaurus is capable of living in groups of 3 - 4 individuals, perhaps family members. However, the fourth segment of Deserts also depicts a lone Tarbosaurus, either one living a solitary lifestyle, or simply one that temporarily ventured off from its pack.

“ Much like everyone else, the hunter is here just for water. ”

― David Attenborough, Deserts

When it comes to interactions with other species, Tarbosaurus is also shown not getting into unnecessary conflict, just like any other rational organism. In the second segment of Deserts, while one responded in annoyance after being accidentally woken up by a Velociraptor chasing a lizard, it chose not to exert energy and pursue what it considered as a minor, temporary disturbance. In the fourth segment of Deserts, a herd of Barsboldia make way for Tarbosaurus to avoid a possible attack, but the predator simply ignores them to take a drink of water. In the second segment of Badlands, a group of Tarbosaurus drives a herd of sauropods traversing through a maze of canyons into a panic without actually launching an attack. This results in one Nemegtosaurus falling off a low ledge and dying in the process, allowing the Tarbosauruses to feed without having put themselves at risk in a physical battle.

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Trivia

• It is unknown how exactly dinosaurs drank water. Prehistoric Planet chose to depict various types of dinosaur drinking water in different ways, with theropods shown scooping up water with their lower jaws rather than lapping it with their tongues or sucking it up. In the fourth segment of Deserts, Mononykus, Therizinosaurus, and Tarbosaurus drink water in this manner, and Tyrannosaurus is later depicted doing the same in the second segment of Freshwater.

References

General

Dr. Darren Naish

Dr. Kenneth Carpenter

Dr. Thomas Holtz