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Tyrannosaurus Rex and Triceratops prorsus

Tyrannosaurus Rex - T Rex

The tyrannosaur is indisputably the most famous dinosaur of all times but also the biggest meat-eater that ever lived in north america. Who can boast of such an exploit?! It’s popularity stems from it’s very wide media coverage in cinema and television. Being cast as the villain in Steven Spielberg’s blockbuster movie Jurassic Park helped propel T-Rex notoriety to unequaled heights. The Tyrannosaurus Rex is to land predators what the Great White Shark (or maybe the Megalodon Shark?) is to the ocean. It also has a renowned exhibition at the American Museum of Natural History in New York.

The name Tyrannosaurus Rex is greek for “King of the tyrant lizards” and this monster wears it to perfection. Measuring close to 13 meters long and 6 meters high, T Rex was feared by all living things and inspired a feeling of generalized terror in all those unfortunate enough to live in the same ecosystem as this creature. This large theropod dinosaur is part of a larger family of dinosaurs known as tetanurans which are more closely related to birds than to Ceratosaurus and is easily recognizable by it’s very small arms and two-fingered hands. Albertosaurus is also another kind of tyrannosaur that is well known and appreciated by dinosaurs enthousiast and alike.

Island continent of Laramidia

Island continent of Laramidia during Late Cretaceous
Laramidia - North America during Late Cretaceous

The Tyrannosaur reigned as master and king leaving chaos and destruction along it’s path during the late Cretaceous era (65 mya) in what is now western america. However back then this region of the globe was an island continent known as Laramidia and spanned from current Alaska all the way down to Mexico. This part of the world once boasted a very impressive and diversified dinosaurs fauna and was home to a wide variety of animals: tyrannosaurs, ceratopsians, hadrosaurs, pachycephalosaurs, dromaeosaurs and titanosaurus sauropods to name a few. These days, the American West is a great place to go fossil hunting as they are found in large quantities.

Jurassic Park cult scene

Up to 500 lbs of meat per bite

This fearsome prehistoric carnivorous beast feasted on the flesh of the unfortunate animals that fell prey to it. Scientists believe that this powerful predator was able to swallow up to 500 pounds (230 kilograms) of meat in a single bite. Fossilized prey of T Rex, including Triceratops and Edmontosaurus, suggests that it broked and crushed their bones while eating them alive; broken bone fragments have been found in Tyrannosaur’s poop. Equipped with a set of 50-60 large teeths the size of a banana, the jaw of this animal was simply unbelievable.

A smart creature

But as if Tyrannosaur gargantuan size and strong jaw wasn’t already enough to make it the apex predator of late Cretaceous western america, it was also endowed with great intelligence boasting a brain twice as big than that of other carnivorous giants. Researchers also believe that Tyrannosaurus Rex could run at speeds averaging 20 km/h. While T Rex wasn’t the fastest of dinosaurs, to the delight of his poor victims who were able to reach velocities of 60 km/h, it would still be able to catch most human beings if it was still around today. The usefulness of Tyrannosaur small clawed arms remains a mystery up to this day. Many scientists think that they could help these skilled hunters grab and chop their preys.


Tyrannosaurus Rex skull
David Monniaux - Wikimedia commons

Up to now, more than 20 Tyrannosaur skeletons – most of them almost fully complete – have been unearthed. The most perfect specimen, nicknamed Sue, was discovered in 1991 by a group of fossil hunters in an isolated South Dakota ranch in the United States. All T Rex bones known to this day were found either in the United States or in Canada in sediments dating back to the late Cretaceous period. The first discoveries of Tyrannosaurus Rex were made by a fellow named Barnum Brown who was then working as assistant curator for the American Museum of Natural History ; in 1900, Brown unearthed a partial skeleton of Tyrannosaur from eastern Wyoming layers, Montana. Two years later, in 1902, Brown found another partial skeleton but this time in the Hell Creek formation, also located in Montana. This later discovery consisted of approximately 34 fossilized bones. Barnum Brown was at first completely disconcerted by his finds since he had never seen anything like this from the Cretaceous era. However, it took an additional three years for Henry Fairfield Osborn, then president of the American Museum of Natural History, to name the fossil discovered by Barnum Brown Tyrannosaurus Rex in 1905. Decades later, in the 1960s, a new wave of interest in the Tyrannosaurus resulted in the recovery of 42 skeletons in North America. But the biggest discovery was made by an amateur paleontologist named Sue Hendrickson who has dug out the largest and most complete (about 85%) Tyrannosaur fossil found.

Specimen of Sue

Sue's fossil exposition

Interestingly, Sue's specimen has been the subject of many legal battles for its acquisition. In 1997, it was the original owner of the land, Maurice Williams, who was granted the right of ownership. The fossil collection was subsequently auctioned by the Natural History Museum for a whopping $ 7.6 million, making Sue the most expensive dinosaur skeleton in the world. Museum staff apparently spent more than 25,000 hours removing bone from the rocks. Since May 17, 2000, Sue's fossil has been exhibited to the general public at the Chicago Museum of Natural History. Extensive scientific studies of Sue's fossilized bones have shown that Sue reached adult size at age 19 and died at age 28; the longest life estimated for a Tyrannosaurus Rex.

Specimen of Stan

Stan fossil exposition

The second most complete T Rex fossil, known as Stan, was also found by an amateur paleontologist named Stan Sacrison in a Hell Creek formation in 1992. The fossil is 70% complete and counts 199 bones.


The Tyrannosaurus had very strong thighs and a powerful tail which allowed him to counterbalance the weight of his huge head and made it very fast on his paws. According to a recent 2011 study that modeled the muscle distribution and center of gravity of the T Rex, this giant theropod could move at speeds between 17 and 40 km / h, which confirms the initial estimates. His two arms were so puny that it is highly unlikely that he could use them to kill his prey or even to bring food to his big mouth. However, if the Tyrannosaurus possessed arms so small it is that its bite was all the more devastating. It is estimated that the Tyrannosaurus Rex could bite with a force of 12,800 pounds, leaving absolutely no chance of survival for its unfortunate dying victims. This roughly corresponds to the force required to lift a school bus from the ground or the weight of a medium-sized elephant. The sharp, conical-shaped teeth of this ferocious predator were used to pierce and grasp the pulpit, which was then torn by rocking movements on each side of his body, initiated by his vigorous musculature. The largest fangs found in this large carnivorous dinosaur were 12 inches long (30 centimeters).

The king of the dinosaurs needed strong and dense neck muscles to keep his large skull in place and power his strong jaw. The muscles of the neck and arms compete for space in the shoulders and it seems that in the case of Tyrannosaurus Rex the cervical muscles have taken over. What's more, long arms are more easily broken, vulnerable to disease and require more energy to maintain, so having small arms could be a beneficial adaptation for this dinosaur.


Tyrannosaurus Rex ancestors
Tyrannosaurus Rex ancestors

The T Rex was perhaps a huge beast, but its predecessors were all relatively modest in size. The first tyrannosaurs appeared about 170 million years ago during the Middle Jurassic period and were barely bigger than a horse. Although not very imposing and threatening, these dinosaurs had a very developed brain and sharp sensory systems. Some finds made on a Middle Cretaceous tyrannosaur revealed that the intelligence of this dinosaur grew when it was still small and allowed it to become the apex predator when it reached the size of the Tyrannosaurus Rex that we know today.


The T Rex was a large carnivore and fed mainly on herbivorous dinosaurs such as Triceratops and Edmontosaurus. This predator obtained its food by searching and hunting in the woods near the rivers. His growth was very fast and it ate hundreds of pounds of meat at a time. The Tyrannosaurus Rex was probably an opportunistic creature contented with dead dinosaur carcasses, although this food source was probably not very abundant. But when no carcasses were available in the area and hunger was felt, the T Rex had to go out and kill to eat. And when we consider the dimensions of this animal, we can easily imagine that it had to eat phenomenal quantities of meat to sustain his growth! For several years the evidence of the predatory nature of the Tyrannosaurus was only circumstantial and included such things as bones with traces of bites, teeth near carcasses and footprints suggesting pursuit. A study conducted in 2013, however, confirmed the evidence when we discovered a tyrannosaurus tooth embedded in a dinosaur coccyx that eventually healed; the dinosaur managed to escape and survive. The Tyrannosaur sometimes also engaged in cannibalism, although it is not known whether it was a scavenger cannibal or whether this species was so territorial that it engaged in mortal fights with members of its own kind. Scientists are still uncertain about the social nature of this great carnivorous theropod.

Where and when lived the Tyrannosaurus

Tyrannosaur fossils were found in a wide variety of Maastrichtian age rock formations dating back to the Late Cretaceous period, which spanned 2 million years towards the end of the Mesozoic era. These beasts are part of the last non-avian dinosaurs to exist before the extinction of the Cretaceous-Paleogene that completely destroyed the dinosaurs. More mobile than most other terrestrial dinosaurs, the Tyrannosaurus Rex roamed the western part of North America in a forested area that was then the island continent of Laramidia.


The Tyrannosaurus Rex is a species of tyrannosaurs belonging to the tetanurans Clad, a large family of theropod dinosaurs more related to modern birds than to ceratosaurs.

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