Tarbosaurus

Tuesday, February 21, 2017

Tarbosaurus by Herschel Hoffmeyer

Tarbosaurus (meaning “alarming lizard”) is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China.

Tarbosaurus size by PrehistoricWildlife.com

Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts see this species as an Asian representative of the North American genus Tyrannosaurus; this would make the genus Tarbosaurus redundant. Tarbosaurus and Tyrannosaurus, if not synonymous, are considered to be at least closely related genera. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus.

Skeleton of Tarbosaurus baatar in Barcelona. Author Jordi Payà

 

Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing up to five tonnes and equipped with about sixty large 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 skeleton by Szymoonio

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 NemegtosaurusTarbosaurus is represented by dozens of fossil specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure.

Restoration of Tarbosaurus in Late Cretaceous Mongolian environment by Dimitri Bogdanov

Tarbosaurus hunting and possible prey specialization

The highly developed sense of smell combined with the underdeveloped sight can be used to draw the easy conclusion that Tarbosaurus was adapted more for scavenging than active hunting.‭ ‬However such a quick conclusion may not be the correct one when you look at the fossils of the rest of the animal as well as potential prey items.‭ ‬Dinosaurs,‭ ‬particularly predatory ones,‭ ‬are always studied for signs of stress fractures,‭ ‬injuries and damage caused by repeated actions throughout the animals life.‭ ‬The key area for stress fractures in Tarbosaurus was surprisingly found in the hands,‭ ‬an area that could not be in contact with the ground.‭ ‬The most plausible explanation for the presence of an injury caused by repeated behavior would be contact with another large dinosaur,‭ ‬another of its own kind or perhaps a large prey item.

Tarbosaurus also did not have the acute stereoscopic‭ (‬binocular‭) ‬vision associated with its North American cousins.‭ ‬Some possible prey items were large hadrosaurs like Saurolophus,‭ ‬but there were also titanosaurid sauropods such as Nemegtosaurus.‭ ‬These large dinosaurs would not require exceptional vision to find and hunt and would have quite possibly been slow on their feet making them viable prey for capture.‭ ‬Their size however would require Tarbosaurus to get close and physical to make a kill,‭ ‬a possible explanation for the stress fracture to the hand.

Tyrannosauridae

Many of the other dinosaurs in the region would have been smaller and often swifter than Tarbosaurus,‭ ‬meaning that it would have been restricted to the larger dinosaurs that other smaller tyrannosauroids like Alioramus were better adapted to catch.‭ ‬Whereas the potential is there for Tarbosaurus to have been an active hunter,‭ ‬it may still have had a greater tendency to turn to scavenging to augment its diet than others of its group.‭ ‬It may have even used its sheer size and bulk to intimidate other smaller predators into giving up their kills,‭ ‬behaviour that can be observed in carnivores that are still active predators today.

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