Stegosaurus
Pronounced: STEG-oh-SAW-rus
Stegosaurus (meaning "Roof Lizard"), at around 9  metres long and 4 metres tall, this quadruped is one of the most easily-identifiable dinosaurs, due to the distinctive double row of kite-shaped plates rising vertically along its arched back and the two pairs of long spikes extending horizontally near the end of its tail. "Stegosaurus tails were without question one of the most dangerous weapons ever evolved by a plant-eating animal." (Bakker) Such a weapon appears necessary considering Stegosaurus coexisted with large predatory theropod dinosaurs, such as the fearsome Allosaurus.
The function of the plates has been much debated. Initially thought of as some form of armour, researchers have also proposed that they may have helped to control body temperature.  The plates are covered with grooves and are honey-combed with spaces indicating an abundance of blood vessels throughout. Wind tunnel tests have suggested that the plates are well shaped to gather and dissipate heat.
Their large size suggests that the plates may have served to increase the apparent height of the animal, in order either to intimidate enemies or to impress other members of the same species, in some form of sexual display. The absence of large plates on other Stegosaurid species tends to support the theory that they functioned primarily for species identification.
Stegosaurus is also known for its remarkably tiny brain, at only 80 grams, apparently sufficient for its needs. The enlarged spinal cord at the animal's hips was not, as commonly thought, a second 'helper' brain, but a junction of major nerves and fat storage.
 Utahraptor
Pronounced: YOO-tah-RAP-tor
 Utahraptor (meaning " Utah thief") is the largest known member of the theropod dinosaur family Dromaeosauride and dates from the upper Barremian stage of the Lower Cretaceous period (126 million years ago).
Six metres long and two metres tall Utahraptor is known from a well-preserved skeleton found in 1991 in Utah, USA and fragmentary remains from South America. It was the largest of a group of lightly-built carnivores, called the dromaeosaurs ('swift lizards'). Utahraptor had large eyes, long grasping hands with large, sharp ripping claws. The second toe of the hind leg features a huge sickle-claw, which could be flicked in a stabbing or slicing motion, like a 750 kilogram kick-boxer. Its toe joints were specially enlarged so that its massive claw could be raised upward and backward to avoid damage while running. But when used in attack, its claw flexed forward as the animal kicked out.

To help it balance on one foot while kicking, its tail was made to act like an acrobat's balancing pole, being stiffened by a sheath of fine bony rods. Swinging in a wide arc its huge 20 cm slashing claw would produce terrible wounds enabling a Utahraptor to cripple and kill animals much larger than itself. The discovery of a number of skeletons of the closely related dromaeosaur, Deinonychus, around the skeleton of a large plant eater suggests that dromaeosaurs may well have hunted in packs.
The unique wrist-joints of the dromaeosaurs allowed the hands to pivot sideways, an action similar to the folding of a bird's wing. Recent discoveries in China suggest that perhaps these creatures were covered in filaments, or 'proto-feathers' for insulation. The dromaeosaurs' relationship to birds is still being explored and debated.
Tyrannosaurus Rex
Pronounced: tie-RAN-oh-SAW-rus Rex
 Tyrannosaurus (meaning "Tyrant Lizard"), T. rex was one of the largest terrestrial carnivores of all time. It stood approximately 4-5 metres high, was about 12-15 metres in length and roughly six tonnes in weight. Tyrannosaurus's massive skull was balanced by a long, heavy tail. The heavily reinforced skull of T. rex suggests that it was a devastating predator, with bone-crushing bite strength. The jaws were armed with 150mm long, sharp, serrated teeth. While some have theorised that T. rex was primarily a scavenger, the powerful structure of head and neck implies that the animal had to withstand violent impacts as it ambushed its prey.  The thick neck muscles would have enabled T. rex to twist and pull with enormous force, tearing away huge chunks of flesh and bone.
Relative to the large and powerful hind limbs, Tyrannosaurus forelimbs were small and retained only two digits. Recent specimens have shown the tiny arms to have been well-muscled, presumably to enable the animal to anchor itself to the ground as it attempted to straighten its hind legs and stand up from a prone position.
Fossils of T. rex have been found in North American rock formations dating to the very end of the Cretaceous Period (late Maastrichtian stage, 65 million years ago); it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction event . More than 30 specimens of T. rex have now been identified, some nearly complete, which has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits and potential speed of T. rex remain controversial. The most recent research on Tyrannosaurus locomotion suggests a range from 17 km/h which would be only walking or slow running, to 40 km/h which would be moderate-speed running.