The Jurassic Period
A few dinosaurs of the Jurassic
During the Jurassic, the supercontinent Pangaea split in two: the northern part is known as Laurasia and the southern part is known as Gondwana. The arid deserts of the Triassic were transformed into thick rainforests because more coastlines had been created by the splitting supercontinent. The dinosaurs dominated the land, marine reptiles swam in the oceans and other reptiles took to the skies.

Stegosaurus (say steg-uh-SAW-rus)

Stegosaurus lived about 160-145 million years ago during the late Jurassic Period. It was over 8 metres long and weighed about 2 1/2 tonnes

Stegosaurus had a big tail with metre-long spikes at the end for protection against predators.The back legs were twice as long as the front legs. It had a tiny head containing a tiny brain. Its mouth was a toothless beak. It had large, flat, triangular plates along its back, rather like armour. Palaeontologists believe that the triangular plates along the back and tail helped it keep its temperature under control. They may also have been used to attract other stegosaurs. They were made of bone that was not solid, but which had tunnels like tubes along them.

The first Stegosaurus fossil was discovered in Colorado, USA in 1877.

Allosaurus (say al-oh-SAW-rus)
The name means 'different lizard', because its vertebrae (bones of the spine) are different from that of other dinosaurs. Allosaurus lived about 150 to 145 million years ago in the Late Jurassic period. It was about 12m long and weighed up to 3 tonnes

Allosaurus was a 'lizard-hipped' dinosaur (or theropod). It had a bony crest above each eye and an s-shaped neck. It moved on its two strong back legs.

The back legs had three toes pointing forward and one pointing backwards. It was not a fast runner however. It had a powerful tail.

Allosaurus was a carnivore with big, curved teeth that were grooved for extra sharpness. The strength in its back and neck helped its jaws tear up its prey. Allosaurus had short arms with three long claws that held onto prey such as large sauropods. Allosaurus had quite short arms compared to its legs, but they were powerful. They had three long, hook-like claws that were important for attacking and holding on to prey.

More than 60 Allosaurus skeletons have been found in Wyoming, New Mexico and Utah in the USA, and Tanzania . The most complete was found in 1883.

Brachiosaurus (say BRAK-ee-oh-SAW-rus)
Brachiosaurus lived about 150 to 145 million years ago in
the Late Jurassic period. Its name means 'arm reptile', because its front legs are much longer than its back legs.

Brachiosaurus was a dinosaur in the group known as sauropods. It was about 25m long and about 13m high. It was able to eat from the tallest trees, feeding on leaves and fruit with its chisel shaped teeth.

Brachiosaurus was one of the biggest land animals ever, probably weighing about 80 tonnes. Good fossils have been found in Colorado, USA and Tanzania.

Diplodocus (say dip-LOD-oh-kus)
The name means 'double beamed lizard' because it had extra bones to help support its spine.

Diplodocus lived about 150 to 145 million years ago in the Late Jurassic period. It was part of the group of dinosaurs known as sauropods. The Late Jurassic period was a time when there were many sauropods.

Diplodocus was a 'lizard-hipped' dinosaur that was about 45 metres long. Much of its length was the tail, which flicked like a whip. Diplodocus weighed about 30 tonnes. Its height at the hips was about 5 metres. It was the longest of the dinosaurs, but not the heaviest. Its brain was not much larger than a tennis ball, but there were many nerves in the base of its spine. This was necessary for it to cope with such an enormous size and to control its tail and back legs.

Diplodocus was a herbivore. It had peg-like teeth which it used for stripping off soft leaves such as those of ferns. The teeth were not used for chewing however. Diplodocus swallowed stones which helped grind up food in its stomach. This habit is similar to that of modern birds.

Fossils have been found in the Rocky Mountains, Montana, Utah, Wyoming and Colorado in the USA.

Camptosaurus (CAMP-toe_SAW-russ) was a plant-eating dinosaur. They probably spent time moving on two legs as well as all four. The front arms had five fingers, and were much smaller than the hind legs, which ad four toes. The long snout had a beak at the front. There were hundreds of grinding teeth at the back of its mouth. It had cheeks much like ours, so could chew and swallow in the way we do. Other dinosaurs swallowed their food whole.

Compsognathus (comp-sog-NATH-us) was about 60cm long and weighed about 3 kg. It was about the size of a modern chicken. It apparently moved incredibly fast and had excellent vision. It was a carnivore and probably hunted by night in packs because that is a more effective way for such small animals to hunt. It was once thought to be the smallest dinosaur, but now microraptor holds that place.

Kentrosaurus (ken-tro-SAW-russ) is related to stegosaurus. It had plates which narrow and turn into spikes along its back and tail. It is thought that it could move its tail very quickly as a defence. Its back legs were longer than its front legs. It was a herbivore, or plant eater.

If you use any part of this, acknowledge it in your bibliography like this:
Sydenham, S. & Thomas, R. The Jurassic Period [Online]

Back to Dinosaur pages index
Back to Animals
updated October 2013©