Pinacosaurus was medium-sized, armored, beaked, quadruped with a slender build. It had a tail club, bony spikes along its back and tail, but didn't have armor on its snout. Pinacosaurus had flared nostrils, four large hoof-covered toes on its front feet and five toes on each of its rear feet.

Pinacosaurus stunned its attackers by hitting them with the bony club on its tail.

Velociraptor had a sharp, deadly, sickle-shaped, retractible, 3.5 inch (9 cm) long claw on each foot (located on each second toe). Velociraptor may have been able to run up to roughly 40 mph (60 km/hr) for short bursts. Velociraptor was a small dinosaur, but a highly efficient killer.

Velociraptor probably hunted in packs, like modern dogs, as this would have allowed them to tackle prey considerably larger than them.

Pachycephalosaurus was a bone headed dinsosaur. It possessed a thick domed skull cap, suitable for butting heads with competing males.

Pachycephalosaurus walked on two legs, had 5 fingered hands, 3 toed feet, and had a long heavy tail. Pachycephalosaurus roamed in herds across parts of North America and Central Asia.

Pterodactyl was a small, flying reptile that lived during the time of the dinosaurs. It was not a dinosaur, but type of extinct, flying reptile.

Pterodactylus had a 2.5 to 3.1 foot (0.75 - 1 m) wide wingspan. It was lightly built, with hollow bones, a long, curved neck, a long skull (with no crest), a long, pointed beak, many small teeth, a small body, and a very short tail. It had a relatively large brain and good eyesight. The skull was about 2.4 inches (6 cm) long.

Pterodactyloid wings were covered by a leathery membrane. This thin but tough membrane stretched between its body, the top of its legs and its elongated fourth fingers, forming the structure of the wing. Claws protruded from the other fingers. Pterodactylus could flap its wings and fly with power.

People have been finding fossils of dinosaur bones for hundreds of years, although they have not always always known what they were - some thought they were the bones of human giants? It was only in the 1829's that people began to realize they were the remains of giant reptiles, now extinct.

The most common fossils are bones and teeth, the hard parts of the animal that resist the processes of decomposition. The second most common fossils are footprints.

Coprolites (fossilized dinosaur droppings) can be dissected, along with gut contents and stomach stones, to reveal details of diet.

Although impressions of dinosaur skins have been found, nobody knows what colour dinosaurs were, as skin decomposes too quickly to fossilize.

At the end of the Cretaceous period, about 65 million years ago, the dinosaurs became extinct. Palaeontologists have been unable to give a completely satisfactory explanation for this, but there are several theories.

One suggests that a star exploded close to Earth and covered the planet in deadly radiation.

Evidence of an enourmous underground crater in Yucatan, Mexico, suggests that a giant meteorite collided with Earth, causing a huge explosion. This in turn caused a thick blanket of dust to form in the atmosphere, blotting out the sun for several months and causing complete distruption to life on Earth.

Other scientists believe the dinosaurs died out as a result of a gradual climatic change. Winters became colder, or summers hotter, favouring the survival of small land mammals which were able to hibernate. We will probably never know for sure.