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Roger Weller, geology instructor

Tyrannosaurus Rex
by Neyda Blaine
Physical Geology
Spring 2009


                Tyrannosaurus Rex: King of the Dinosaurs

Jon Hughes of

Millions of years ago, before humans existed, dinosaurs ruled the earth. Dinosaurs came in different shapes and sizes. Tyrannosaurus rex, perhaps the world’s most famous dinosaur, was discovered and named by American geologist Henry Fairfield Osborn in 1905. Tyrannosaures rex, which means “tyrant lizard king,” is also called T-rex. This creature was one of the biggest carnivorous dinosaurs in the cretaceous period and was the largest in the Tyrannosaur family of dinosaurs, also known as Tyrannosauroidea. They had small arms and two-fingered hands with long claws. The third finger was very tiny. However, T-rex measured 40 ft (12 m) long and 15 to 20 ft (4.6 to 6 m) tall, the size of a bus. T-rex also weighed 5 to 7 tons.  In addition, T-rex had rough, bumpy skin, similar to that of an alligator. It had a pointed tail which helped it balance its huge head. Its head was as big as an average twelve-year-old kid. The tail helped this species move fast with quick turns. This fierce predator had razor sharp teeth that measured about 5-10 inches long. It was big enough to swallow a human and the teeth easily crunched through thick dinosaur bones. The primary consumer of the Triceratops dinosaur, which was herbivore, was Tyrannosaurus rex.

Photo Copyright R. Weller/Cochise College and the Natural History Museum.



The world today is nothing like it was during the Cretaceous period. The shape of the continent was different. The continents were two large landmasses called Gondwana and Laurasia. After the Cretaceous period, toward the end of the Mesozoic, the earth’s movements altered the landmasses of the earth and different continents began to develop from the fractured landmasses, which are those we see today. Different types of dinosaurs evolved on distinct landmasses over time. Tyrannosaurus rex was one of the last dinosaurs to have lived in the late Cretaceous period, toward the end of the Mesozoic Era, which is about 65 to 85 million years ago. T-rex lived in the vast forest that would be the western part of North America.  


Hunter or Scavenger?

            Diet among dinosaurs was based on the kind of teeth they had. T-rex had long, razor-sharp teeth, which indicated he was a carnivore. Yet, not all carnivores killed their prey. Paleontologists cannot be certain how T-rex got the meat he ate. Many paleontologists disagree on whether this scary and impressive dinosaur was in fact a scavenger or a hunter. If T-rex was a scavenger, he would have looked for animals that were already dead, instead of chasing live prey. According to paleontologists, evidence contradicting the scavenger theory includes the strong massive skull bones that could easily handle any type of collision occurred when T-rex attacked another dinosaur. Another argument in favor of T-rex as a hunter is the position of its eyes, which face forward like a humans and not to the sides, like most animals that are hunted and have no depth perception. Having eyes forward makes it easier to know exactly where things are. However, there is contradicting evidence for T-rex as a hunter. After studying the dinosaur’s legs, paleontologist found that T-rex could only maintain a speed of 25 miles per hour sprint, which is very slow compared to many dinosaurs, making it difficult for him to catch his prey. Another theory suggesting that T-rex was a scavenger is the animal’s strong sense of smell, which was similar to that of a vulture, which can smell rotting meat from a great distance. Perhaps T-rex was a scavenger and a hunter like many carnivores in the world today.



            In 1990, a Tyrannosaurus rex fossil was discovered by hunter Sue Hendrickson in the Badlands of South Dakota. Today it is the biggest and best preserved fossil. This fossil is named Sue and it took years to dig up its remains and to prepare it for display. Sue’s remains confirmed to paleontologists that dinosaurs like T-rex fought one another. Sue showed evidence of cured facial injuries that were probably from the same species. However, nobody knows for sure whether Sue is a male or female. A total of about 30 T-rex skeletons have been found so far and some of them are not well complete. Other fossils such as a dinosaur’s excrement, also called coprolite, inform paleontologists about dinosaur diets. Although fossils reveal an immense amount of information, they cannot tell us what color T-rex was. However, some animal predators today have a dull color, which prevents them from being spotted away. Based on new discoveries in China, some paleontologists believe dinosaurs descended from birds. Some fossils show evidence that dinosaurs had feathers. There are also similarities in the appearance of both dinosaur and bird skeletons. In addition, dinosaurs hatched from eggs, like birds, and evidence suggests that some baby dinosaurs had feathers to keep them warm. Studies of the soft tissue from T-rex femur bone reconfirm that birds are the closest living relatives to dinosaurs. Many fossiled eggs continue to be found. The first one was found in France in 1869. They were long, thin and shaped like footballs and many have been found in different parts of the world. Another interesting fact about T-rex is that many skeletons are usually found alone, indicating that this animal was a solitary creature. However, still nobody knows if T-rex lived in a pack or not.



  Photo Copyright R. Weller/Cochise College and the Natural History Museum.


Dinosaur Extinction

            No one knows exactly why the dinosaurs died. However, there are conclusions made about an immense asteroid that hit the earth. Paleontologists refer to this impact as the K-T boundary. It exists today and it is called the Chicxulub crater. It is located off the Yucatan Peninsula in Mexico. The crater, the majority of which is covered by sea, is over 111 miles (179 km) across. Some paleontologists have concluded that this impact perhaps caused major changes in the climate. The dinosaur’s food chain went into turmoil causing the plants to die and those who were herbivore had nothing to eat and the carnivores like T-rex would eventually lose their prey, eventually eating each other and then starving to death.


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