The Jurassic period

Dinosaurs lived during the three periods of the Mesozoic era: the Triassic, the Jurassic and the Cretaceous. The Jurassic period was the second of these periods, lasting from 206 to 144 million years ago.

The Jurassic period and its conditions

The Jurassic period experienced slightly cooler conditions than those found in the Triassic period. The climate was still quite warm, however. The climate during the Jurassic period was also a lot more humid than it had been during the Triassic period. This caused rivers, lakes and swamps to form around the world, as well as lush vegetation. During this time, Pangaea began to break up, causing Gondwanaland to separate from Laurasia. Australia experienced warmer temperatures and high rainfall, causing rivers to criss-cross the modern-day continent.

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As the climate became wetter around the world, plant life flourished. Coniferous forests dominated the landscape, with ginkgoes, palms, tree ferns and horsetails also flourishing. Flowering plants had not developed by the Jurassic period.

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Early birds developed in the Jurassic period, although pterosaurs were still the dominant flying animals. Insects included the ancestors of modern bees and flies, while aquatic animals included ichthyosaurs, plesiosaurs, fish and molluscs.

Jurassic period dinosaurs around the world

The Jurassic period saw a wide expansion of dinosaur species. Larger dinosaurs evolved during this period, although smaller dinosaurs also continued to thrive. These larger dinosaurs were both carnivorous and herbivorous. The largest dinosaurs were herbivores called sauropods, which were enormous, four-legged creatures with long necks. One of the most famous of the sauropods was Brachiosaurus, which lived in places like North America and Africa about 150 million years ago. Brachiosaurus was 25 metres long and 12 metres tall, and it had a mass of 30 to 50 tonnes. Owing to its size, Brachiosaurus would have needed to eat around 200 kilograms of food every day.

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Plant eaters were not the only large dinosaurs, however. Large theropod predators, like Allosaurus, also lived during the Jurassic period. Allosaurus lived about 140 million years ago, near the end of the Jurassic period, in North America, Africa, Australia, and possibly Asia. Allosaurus was 12 metres long and had a mass of 2-5 tonnes. A pack of Allosaurus could take down a Brachiosaurus or similarly-sized dinosaur, while an Allosaurus on its own might be able to hunt and kill a smaller animal like a Stegosaurus.

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Jurassic period dinosaurs in Australia

There is more evidence of dinosaurs in Australia from the Jurassic period than from the Triassic period. A partial skeleton of a large sauropod called Rhoetosaurus brownei was discovered in south-east Queensland. Rhoetosaurus was one of the oldest-known sauropods, existing around 170 million years ago. It was 12 metres long. Like other sauropods, it had a long neck, but its neck was not quite as long as that of Brachiosaurus. This may be because Rhoetosaurus was at an earlier stage of its evolution than Brachiosaurus.

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Smaller dinosaurs lived in Australia as well as larger ones like Rhoetosaurus and Allosaurus. Evidence exists for a small ornithopod dinosaur with a length of only one to two metres. This dinosaur fed on plants and its footprints have been found in central Queensland.