Jurassic Park

Scientists believe the longest dinosaur that roamed the earth during the Jurassic Era was the Diplodocus. (Follow the link to the BBC’s video recreation of this sauropod.) These enormous plant-eating creatures weighed up to 30 tons.

A "lizard-hipped" dinosaur whose digestive system processed plant material with the help of stones that the animal swallowed, its fossilized remains have been found at the Morrison Formation (in the western United States) and on all other continents except Antarctica.

Despite its length, Diplodocus was dwarfed by its fellow-inhabitant of the Jurassic Age - the long-necked Brachiosaurus.  A skeleton in Berlin’s Natural History Museum is 13 meters (about 40 feet) high. Its upper arm bone is more than 6 feet long.

Remains of Stegosaurus, another plant-eating Jurassic dinosaur with spiny spindles (first drawn by Othniel Marsh 100 years ago), have been found throughout the world. Smaller than Diplodocus, it weighed seven tons. But the most likely ancestor of T-Rex, the Eustreptospondylus, has only been found in England. Due to limited fossil remains, scientists are unsure about the average size and weight of this carnivore.

One of the real giants of the Jurassic Age - or of all times - was the Liopleurodon.  With teeth twice the size of the later T-Rex, this ocean creature used its monstrous mouth to end the lives of its prey. Paleontologists today are able to study its eating habits from the fossilized remains of its victims.