Tyrannosaurus rex, otherwise known as T. rex is perhaps the most famous creature known from the fossil record. It is certainly a very well-known dinosaur, but ironically new evidence has emerged over the last decade or so that challenges some of the long held public perceptions regarding this prehistoric monster.

T. rex the World's Most Popular Dinosaur?

Ask a small child what their favorite dinosaur is and it is quite likely that they will say Tyrannosaurus rex. This dinosaur is often referred to as the "superstar predator" of the Late Cretaceous, but just how big and fearsome was this dinosaur? There were other dinosaurs that were bigger than T. rex? Does this dinosaur deserve the name "king of the tyrant lizards"?

Tyrannosaurus rex is a member of the Tyrannosaurid dinosaur family. This type of meat-eating dinosaur evolved sometimes in the Jurassic and as a group they remained relatively insignificant until the Late Cretaceous when they evolved into a number of giant forms and become the apex predators of the northern hemisphere, most notably in Asia and North America . As to the exact origins of the Tyrannosaurs, this remains unclear. Eotyrannus ( Eotyrannus lengi ) known from a single skeleton discovered on the Isle of Wight (England), shows a number of Tyrannosaur characteristics and some scientists have suggested that this group of dinosaurs originally originated in Europe. However, some scientists argue that the Tyrannosaurs originated in eastern Asia, citing fossil discoveries such as Guanlong ( Guanlong wucaii ) from Late Jurassic strata in China as evidence that the ancientors of T. rex were from the Orient.

As a group, the Tyrannosaurids had large, heavy, broad skulls. The jaws were lined with massive, slightly recurved teeth with both sides of each tooth serrated like a saw blade. The teeth, particularly those of later, larger Tyrannosaurids such as T. rex, Gorgosaurus and Daspletosaurus were thickened and in cross section rather D-shaped. The front limbs were very much shorter than in other groups of Theropods such as the Allosaurids. In the last of the Tyrannosaurs, these arms ended in two-fingered hands, with each finger having a sharp claw on the end. The tail was long and muscular and helped these creatures balance. Ironically, T. rex is relatively well represented in the fossil record when compared to other Late Cretaceous meat-eaters. A number of good quality, almost complete skulls are known, the largest of which measures a fraction over 1.7 meters in length.

The skull of Tyrannosaurus rex was powerful enough to crack bone. Assessments on the bite force of this predator indicate that this animal had one of the strongest bites of all animals known to science. The heavier lower jaw had a flexible joint in the middle of it, this trait is found in a number of other unrelated dinosaur meat-eaters. This joint allowed the jaws to flex so that the mouth could be opened very wide to take in extra large pieces of meat and bone. The large orbit (eye socket) indicates that this dinosaur had an excellent vision. Measurements taken regarding the approximate size of the optic nerve entering the brain from the eye suggest that this nerve was at least two centimetres thick in large specimens. This would indicate that a great deal of data was being transmitted from this dinosaur's sense of sight into the brain. It had forward facing eyes, giving T. rex stereoscopic vision, a terrific advantage especially when it is considered that T. rex could view the world from fourteen feet in the air – its head perched on top of its powerful neck.

In terms of size, the largest Tyrannosaurus rex is known as a robust form, that is currently mounted in the Chicago Field Museum (Chicago, United States). Believed to be a female, this specimen measures over forty-two feet in length and scientists have estimated that this particular animal could have weighed as much as 7,000 kilograms. Discovered in the Badlands of South Dakota in the early 1990s this specimen is the largest mounted Tyrannosaur skeleton in the world. However, rumors of an even larger Tyrannosaurus rex fossil are circulating around scientific circles. The skull, although not completely excavated is believed to be a good six inches larger than that of Chicago Field Museum specimen.

Even with this new Tyrannosaur discovery, there were a number of other dinosaurs that were much larger than T. rex. Firstly, a number of plant-eating dinosaurs were much, much larger, but even in the world of flesh eaters there are several candidates to compete with T. rex for the title of largest meat-eating dinosaur known to science.

Remaining within the Tyrannosaur family we can come across two potential rivals to Tyrannosaurus rex – animals such as Tarbosaurus ( Tarbosaurus bataar ) from the Late Cretaceous of Mongolia. The larger of the two Tarbosaurus skeletons mounted in the Palaeonological Institute of the Russian Academy of Sciences in Moscow (Russia) measures nearly forty feet long. Then there is the newly discovered Chinese Tyrannosaurus, known as the "Tyrant from Zhucheng city" – Zhuchengtyrannis magus. This Late Cretaceous meat-eater was only described in April of this year. It is known from an almost complete skeleton recovered from a dig site over the last twelve months or so. The lower left jawbone (dentary) is almost complete and measures over a meter in length, indicating an animal perhaps as big as Tyrannosaurus rex.

Then we have to consider the other contenders, dinosaurs that were carnivores and bigger than Tyrannosaurus rex. Perhaps the best known of these is Giganotosaurus ( Giganotosaurus carolini ). The fossils of this dinosaur were first found in Argentina in 1994 and typically described a year later. Giganotosaurus was a member of the Allosaur family, it has been estimated to be nearly fifty feet in length and possibly weighed as much as eight thousand kilograms. Then there is Carcharodontosaurus ( Carcharodontosaurus saharicus ), from north Africa. Although, known from only fragmentary material This Allosaur has been estimated to be around forty-six feet in length.

Finally, there is the little known predator which fossils were found in the famous Cleveland-Lloyd quarry in the Morrison Formation (Utah). This dinosaur, also a member of the Allosaurids is known as Saurophaganax ( S. maximus ). The few bones assigned to this genus were discovered before the Second World War, but they were not scientifically studied in detail until the mid 1990s. Little is known about this dinosaur, but estimates suggest that this meat-eater exceeded forty feet in length, rivaling the biggest Tyrannosaurids.

For the time being, T. rex remains the most famous of all dinosaurs, but not the largest land predator of all time. That is until the next T.rex fossil is discovered.

Source by Mike Walley

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