This essay T rex has a total of 968 words and 6 pages.
Biology Block. 2
November 30, 1999
The name says it all. This group of huge carnivores ruled the land during the Cretaceous period. Short but deep jaws, long hind limbs (legs), beady eyes, a long muscular tail, and tiny forelimbs (arms) make up a tyrannosaur. The Tyrannosauridae included such similar animals as Albertosaurus, Gorgosaurus, Daspletosaurus, Tarbosaurus, and of course Tyrannosaurus Rex. A tremendous skeleton of Rex now stands guard in the Valley Life Sciences Building in Washington. Tyrannosaurs belong to the Saurischia, or "reptile-hipped" dinosaurs. Within the Saurischia, tyrannosaurs belong to the group of carnivorous dinosaurs known as theropods. Traditionally, the tyrannosaurs have been included within the Carnosauria. In this classification scheme, carnosaurs represent the largest carnivorous animals to ever walk the land.
Since tyrannosaurs were so huge, you might ask how they could move all that weight around and hunt prey? In the modern dinosaur movie Jurassic Park, T.Rex is depicted moving extremely quickly, maybe 50 or 60 mph! Is this correct? Recently, scientists studied Jurassic Park to calculate the actual speed (using the length of the dinosaur\'s strides) of T. Rex in the movie. They found that it was actually moving at a walking speed of about 12-mph (the jeep in the movie was supposed to be moving at about 40mph)! Many scientists familiar with the
principles of biomechanics (physics applied to living organisms) think that tyrannosaurs could move fairly fast, maybe 10-20 mph, but not as fast as the smaller theropod dinosaurs. Smaller tyrannosaurs like Albertosaurus may have moved faster than the bigger ones like T. Rex. Some think that this was probably true for young tyrannosaurs, too. Yet, we still lack conclusive evidence that tyrannosaurs could even run. Some think that their body size limited them to only a fast walk, like an elephant.
Tyrannosaurs are surprisingly common in many North American fossil beds, especially their large, serrated teeth, which they shed periodically like most archosaurs. The teeth of tyrannosaurs are very interesting. Rather than being the flat knifelike blades as in most other carnivorous dinosaurs, they are more like giant spikes than razor-edged blades. With a mouthful of these murderous weapons, tyrannosaurs had a whopping bite, which might have made up for their reduced forelimbs. The bite marks of these teeth are quite recognizable on some dinosaur bones. Some tyrannosaur fossils show evidence of bite marks from other tyrannosaurs, suggesting that there might have been fierce fighting between tyrannosaurs, and even cannibalism. The rarest tyrannosaur fossils are those of T. Rex, making studying that animal particularly difficult. Most known dinosaurs are represented by only one good specimen, if that much. So T. Rex is not nearly the rarest fossil find of all.
Tyrannosaurus, being the most ferocious of the dinosaurs, weighed over seven-tons. Tyrannosaurus actually means "king of the tyrant lizards." Tyrannosaurus was probably the
largest land predator ever. It stood almost 20 feet tall on it’s rear legs. It had a massive tail, puny front legs, powerful jaws, and sharp seven-inch-long saw-edged teeth for tearing its prey. From nose to tail Tyrannosaurus measured up to 45 feet in length. It’s skull alone was nearly four feet long. These monstrous predators lived toward the very end of the age of dinosaurs. Some paleontologists believe Tyrannosaurus was a scavenger, but most believe it was a fierce hunter, swift on its back feet and ferocious in battle. It most likely preyed on packs of Duck-Billed Platypus as well as herds of the better-defended Triceratops.
Tyrannosaurus Rex lived during the Cretaceous period when both giant continents, Laurasia and Gondwana, began splitting. Mountains began growing and the seasons became more pronounced. Flowering plants spread and by the end of the Cretaceous period, oak trees, hickories, and magnolias were common in North America. The forests began to look almost modern. During this time toothless, bird-like dinosaurs appeared, as did the greatest of the meat-eaters, Tyrannosaurus. But the meat-eaters were matched by heavily armored plant-eaters, such as Triceratops and Ankylosaurus. Duck-billed dinosaurs with mouths designed for eating tough plants were also common. Large flying reptiles and waterbirds soared above the earth and there were many animals that are with us today; lizards, snakes, frogs, salamanders, and small mammals like possums could all be found. Then, 65 million years