LOCALITY: Nemegt, Gobi Desert, Southern Mongolia

AGE: Late Cretaceous (Late Campanian - Early Maastrichtian), Nemegt Formation.

SIZE: 9.5 meters long

MEANING OF NAME:'Alarming reptile'

PRONUNCIATION: Tar-bow-SAWR-us

CLASSIFICATION: THEROPODA: Carnosauria; Tyrannosauridae

When first described, Tarbosaurus bataar was assigned to the North American genus Tyrannosaurus.  The differences between these two fossil reptiles are slight and the two probably played similar ecological roles of predator or scavenger in their respective communities.

Although large, the skull of Tarbosaurus bataar is quite lightweight.  This is because of large air sinuses within the bones, which enabled the skull to be much larger than would have otherwise been possible.  This pneumatisation (formation of air filled spaces) in bones is not restricted to the skull and limb bones but is seen also in the vertebrae.  It is a feature that is common to the saurischian (lizard-hipped) dinosaurs, a group, which includes the giant herbivorous sauropods as well as the carnivorous forms.

The relatively small size of the forelimbs (arms) of Tarbosaurus bataar is not unique to this dinosaur but is common to all the carnosaurs (large meat-eating dinosaurs). This limb size may have helped the two-legged animal with a large head to maintain its balance by limiting the weight of its forelimbs. 

No dinosaur brains have been found. The soft brain tissue quickly rotted away after every known dinosaur died. What is preserved in some cases is a natural mould of those parts of the brain where bones of the skull were next to it.  In reptiles, the top of the brain rests against the top of the skull but the sides and base of the brain are surrounded by large masses of soft tissue which does not fossilize any better than the brain itself.  Therefore, only the top of the brain and the pathways of the nerves coming out of the brain where they pass through bony channels in a skull are preserved.  This makes it difficult to study dinosaur brains, but even with these limitations, it is fair to say that if a mammal were the size of a Tarbosaurus bataar, one would expect its brain to be 10 times larger than the best estimate that can be made for the size of Tarbosaurus bataar's brain.  Tarbosaurus was not a mental heavyweight, to say the least! 

Predators eat many times their own weight during their lifetime.  Therefore, in any balanced natural community over a significant span of time - years or decades, there is a far greater mass of prey species than predators.  This being the case, the fact that about one quarter of the bones found in the Nemegt Formation of Mongolia belong to Tarbosaurus bataar shows that the fossil record is not always an accurate reflection of the real numbers of different animals that lived in an area when the rocks in which their remains are were soft sediments.*

Moving water selectively sorts and preserves certain sizes and shapes of bones.**This certainly occurred in the case of Tarbosaurus bones.

*Fossil beds can only show where dead animals were buried rather than where or how they lived.

**Given the pneumatisation of sauropod bones mentioned above the Tarbousaur bones in the Nemegt Formaton could have been washed together from across a large area and merely have been fossilized together in the formation.