General
Tyrannosaurus Rex litterally means the "King of the Tyrant Lizards". This huge meat-eating dinosaur lived during the late Cretaceous period, about 85 million to 65 million years ago. T-Rex is one of the largest terrestrial carnivores of all time, and it is one of the most famous dinosaurs ever discovered. The recently discovered Giganotosaurus and Carcharodontosaurus are slightly bigger than T-Rex.

Fossils
T-Rex fossils have been found in western North America (Montana) and Mongolia. 

Anatomy
T-Rex was 40-45 feet (12-14 m) long and about 15-20 feet (4.5 to 6 m) tall. It weighed 5.0-7.5 tons. The bird-like feet had three large clawed toes and were about 3.3 feet (1 m) long. But T-Rex walked on its toes and the footprints were only 1.55 feet (46 cm) long. The stride was 10-15 feet (3.0-4.5 m) and T-Rex could run up to 15 mph (24 kph). This lizard-hipped dinosaur had a solid body with hollow bones. The tiny forearms each had two clawed fingers that were too short for feeding or fighting. From fossils it can be seen that T-Rex had a rough, scaly skin like an alligator.

Jaws
At the short and muscular neck was a huge head with well-developed jaw muscles. The jaws were up to 4 feet (1.2 m) long with 50 to 60 replaceable teeth. It must have been a fearsome sight to see the thick, sharp, conical, bone-crunching teeth that were 9-13 inches (23-33 cm) long. T-Rex had a overbite and could eat up to 500 pounds (230 kg) in one bite.

Tail
The slim, stiff, pointed tail provided counterbalance for the enormous head. This gave excellent agility and allowed quick turns while running. It probably extended its tail and head horizontally as it walked with a rolling gait.

Senses
As most predators T-Rex had good senses. Both eyes faced forward which gave depth perception. And the brain had large areas for processing visual information and odors.