Reconstruction of the T. rex type specimen
(CM 9380) at the Carnegie Museum of
Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), is one of the most well-represented of the large theropods. Tyrannosaurus lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 68 to 66 million years ago. It was the last known member of the tyrannosaurids, and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction.
|Sue at the Field Museum of Natural|
Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, located at the Field Museum of Natural History under the name FMNH PR2081 and nicknamed Sue, measured 12.3 meters (40 ft) long, and was 3.66 meters (12 ft) tall at the hips, and according to the most recent studies estimated to have weighed between 8.4 metric tons (9.3 short tons) to 14 metric tons (15.4 short tons) when alive. Not every adult Tyrannosaurus specimen recovered is as big. Historically average adult mass estimates have varied widely over the years, from as low as 4.5 metric tons (5.0 short tons), to more than 7.2 metric tons (7.9 short tons), with most modern estimates ranging between 5.4 metric tons (6.0 short tons) and 8.0 metric tons (8.8 short tons).
The neck of Tyrannosaurus rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs had only two clawed fingers, along with an additional small metacarpal representing the remnant of a third digit. In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.
|T. rex size compared to human|
The largest known Tyrannosaurus rex skulls measure up to 1.45 meters (4.8 ft) in length. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects Tyrannosaurus's skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision. The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids. The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.
|T. rex eating it's prey|
The teeth of Tyrannosaurus rex displayed marked heterodonty (differences in shape). The premaxillary teeth at the front of the upper jaw were closely packed, D-shaped in cross-section, had reinforcing ridges on the rear surface, were incisiform (their tips were chisel-like blades) and curved backwards. The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when Tyrannosaurus bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers, more widely spaced and also had reinforcing ridges. Those in the upper jaw were larger than those in all but the rear of the lower jaw. The largest found so far is estimated to have been 30.5 centimeters (12 in) long including the root when the animal was alive, making it the largest tooth of any carnivorous dinosaur yet found. T. rex's serrated, conical teeth were most likely used to pierce and grip flesh, which it then ripped away with its brawny neck muscles. Its two-fingered forearms could probably seize prey, but they were too short to reach its mouth.
Scientists believe this powerful predator could eat up to 500 pounds (230 kilograms) of meat in one bite. Fossils of T. rex prey, including Triceratops and Edmontosaurus, suggest T. rex crushed and broke bones as it ate, and broken bones have been found in its dung.
Tyrannosaurus rex lived in forested river valleys in North America during the late Cretaceous period. It became extinct about 65 million years ago in the Cretaceous-Tertiary mass extinction.