Tarbosaurus

*Tarbosaurus bataar*

***Tarbosaurus*** was a very close relative to the *Tyrannosaurus rex* in size and also the massive skull which is 4 feet long. *Tarbosaurus* was a large dinosaur about 40 feet long and weighed 6 tons. It lived in Southern Mongolia in the late Cretaceous, 67 million years ago. It was one of the last surviving dinosaurs. New research by scientists suggests that *Tarbosaurus* is so close to *T. rex*, that there is still debate on whether or not to move the species *T. baatar* to the *Tyrannosaurus* genus.

It is believed that *Tarbosaurus* was, in fact, *T. rex* that migrated from North America to Asia through some sort of "land bridge" that connect the two continents during the Late Cretaceous period (around 70-66 million years ago).

## Description

*Tarbosaurus* can be compared to as a very similar to its more infamous North American counterpart. Its bone-crushing bite would've singlehandedly destroyed its prey, and the estimated stride lengths of these large carnivores would've given it the ability to stalk after prey. *Tarbosaurus* probably picked on some of the herbivores in its area the hadrosaurid *Saurolophus* would've probably supplied it with majority of its prey. *Tarbosaurus* has an unusual huge skull compared to the rest of the body, but was quite light due to the holes in the skull called antorbital fenestrae.

## Paleobiology

Although many specimens of this genus has been found, little definite data is confirmed on the dinosaur as of 1986, though it is presumed and has been shown to share many characteristics with other tyrannosaurids.

During studies of the animal, the upper jaw proved very interesting, as it possessed more than 20 extremely large, knife-shaped teeth. The skull in general seems to have many similarities with its North American cousin, *Tyrannosaurus rex*, prompting many to place it in the *Tyrannosaurus* genus (the resulting designation would then be *Tyrannosaurus bataar*). The close similarities have also prompted some scientists to suggest a possible link between the North American and Eurasian continents at that time, perhaps in the form of a land bridge. The discovery of Lythronax further cements this relationship, as it shows *Tarbosaurus* is most closely related to *Tyrannosaurus,* and *Zhuchengtyrannus* while *Lythronax* stands as the sister taxon to this clade.

Only one species of *Tarbosaurus*, *T. bataar*, has been officially established. *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 about 11m long and 5.5 tonnes in weight. *Tarbosaurus* is unique among *Tyrannosaurids* in that it possesses a locking mechanism in its jaws; possibly an adaptation for hunting sauropods. This locking mechanism also made the theropod's skull more rigid as a result.

While juvenile tyrannosaurids in general are rare, a skeleton of a very young Tarbosaurus (estimated to be two or three years of age) indicates they had very different niches from the adults and may have been nocturnal, based on measurements of their sclerotic rings. Whether the adults were nocturnal as well is not known.

Skin impressions are known from *Tarbosaurus*, and show the animal had non-overlapping scales. However, fossil poachers destroyed the impressions, and as such they can no longer be studied. Footprints attributed to the genus are also known from the Nemegt Formation.

## Paleoecology

*Tarbosaurus* fossils have been found primarily in the Nemegt Formation of Mongolia, and are believed to be early Maastrichtian in age (circa 70 mya). At the time, Mongolia was a seasonal floodplain on the edge of a desert that was prone to long dry seasons and short wet seasons. The resulting environment may have looked similar to the modern Okavango Delta of Africa. Regardless, it was an environment capable of supporting a wide array of large dinosaur species.

*Tarbosaurus* would have shared the Nemegt with many genera and species of animals. While Tarbosaurus was at the top of the food chain, it also shared its environment with other predators, such as the smaller *Alioramus*, another tyrannosauroid belonging to the Alioramini, the dromaeosaurid *Adasaurus*, and troodontids such as *Borogovia*, *Tochisaurus*, and Zanabazar, oviraptorosaurs *Elmisaurus*, *Nemegtomaia*, *Rinchenia* or *Bagaraatan*, (which may actually be a basal tyrannosauroid rather than an oviraptorosaur). Other theropods, like the gigantic *Therizinosaurus*, and ornithomimosaurs such as *Anserimimus*, *Gallimimus*, and gigantic *Deinocheirus* dwelled here as well. Other dinosaurs of note that resided in the Nemegt included *Saurolophus* (also native to North America), ankylosaurids such as *Tarchia* and *Saichania*, the pachycephalosaurid *Prenocephale*, and the titanosaurid *Nemegtosaurus* (which may or may not be synonymous with *Opisthocoelicaudia*). All would have been potential prey for adult *Tarbosaurus*, while adolescent Tarbosaurus may have been forced to compete with Alioramus for food due to occupations of a similar niche.

## Classification

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 femurs 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 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*, 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.

## JPInstitute.com Description

This was a very close relative of Tyrannosaurus rex that lived in China during that Late Cretaceous period. Originally called Tarbosaurus when it was discovered in 1955, it was later renamed Tyrannosaurus baatar after studies and comparisons of the fossils determined that they were from the same family.

This dinosaur is good example of how international cooperation can greatly benefit science, and it also helps to show how genus and species are related. Tyrannosaurus baatar is the same genus, but a different species.

See Tyrannosaurus rex for more information.

## Links

http://web.archive.org/web/20030813133216/http://www.jpinstitute.com/dinopedia/dinocards/dc\_bataa.html

## References

* https://www.nhm.ac.uk/discover/dino-directory/tarbosaurus.html
* https://australian.museum/learn/dinosaurs/fact-sheets/tarbosaurus-bataar/
* https://www.smithsonianmag.com/science-nature/you-say-tyrannosaurus-i-say-tarbosaurus-142897656/
* https://www.app.pan.pl/archive/published/app48/app48-161.pdf
* https://www.livescience.com/20540-tarbosaurus-tyrannosaurus-difference.html
* http://www.gondwanastudios.com/info/tarb.htm
* http://www.dinosaur-world.com/tyrannosaurs/tarbosaurus\_bataar.htm
* https://blog.everythingdinosaur.co.uk/blog/\_archives/2007/08/27/3194599.html
* https://www.researchgate.net/publication/226337077\_A\_new\_study\_of\_the\_brain\_of\_the\_predatory\_dinosaur\_Tarbosaurus\_bataar\_Theropoda\_Tyrannosauridae
* https://www.researchgate.net/figure/The-skeleton-of-tarbosaurus-Tarbosaurus-bataar-The-largest-predator-was-up-to-12-14-m\_fig8\_338327588
* https://www.researchgate.net/figure/Juvenile-Tarbosaurus-bataar-MPC-D-107-7-A-photograph-of-the-specimen-prior-to\_fig1\_232865497
* https://www.researchgate.net/publication/26871213\_A\_long-snouted\_multihorned\_tyrannosaurid\_from\_the\_Late\_Cretaceous\_of\_Mongolia
* https://a-dinosaur-a-day.com/post/107163811085/tarbosaurus-bataar
* https://www.biologiatropical.org/blog/the-mysterious-twin-dinosaurs
* https://www.researchgate.net/figure/Mounting-a-Tarbosaurus-skeleton-in-the-Paleontoo-logical-Museum\_fig4\_263760683
* https://www.researchgate.net/publication/232865497\_Cranial\_Osteology\_of\_a\_Juvenile\_Specimen\_of\_Tarbosaurus\_bataar\_Theropoda\_Tyrannosauridae\_from\_the\_Nemegt\_Formation\_Upper\_Cretaceous\_of\_Bugin\_Tsav\_Mongolia