Australian Dinosaur Story

Formation of the Australian continent

 

When did the dinosaurs live?

Dinosaurs lived in an era that scientists call the Mesozoic, sometimes referred to as the 'Age of Dinosaurs'. This was made up of three periods known as Triassic, Jurassic, and Cretaceous, and spanned the time from about 250 million years ago until about 65 million years ago. Dinosaurs were the dominant land animals, and there were many different species of them. Dinosaur fossils have been found all over the world, including Australia. Scientists that study these fossils are called Palaeontologists.

Why do scientists think this?

Fossils can be dated by using rocks of a known age that contain fossils as a reference point, or by measuring the rate of deterioration of specific minerals found within the rocks. So far, most Australian dinosaurs have been found from the Cretaceous Period with several from the Jurassic Period. None have been proven to be from the Triassic Period.

Did the Earth look the same during the Age of Dinosaurs?

No, when dinosaurs first appeared, the Earth was made up of one big continent. All the landmasses were joined together. This big continent is known as Pangaea.

As time went by, Pangaea gradually broke apart into the landmasses we know today. First it separated into a northern and a southern continent.

The southern continent, which included Australia, was known as Gondwana.

During the Cretaceous Period, Gondwana gradually broke up into the present landmasses of Africa, South America, India, Antarctica, and Australia. Antarctica and Australia were the last continents to separate, starting about 100 million years ago.

Were dinosaurs able to survive while the continents moved?

Yes. The continents would have moved very slowly, perhaps only about 5 centimetres per year (this is about the speed our fingernails grow!). Australia is still moving northwards at about this rate, but we don't notice it.

Did the same species of dinosaurs live throughout the whole of the Age of Dinosaurs?

No, dinosaur species changed over time. In Australia fossils of many different species have now been found. Each species lived for a limited time before becoming extinct.

Why was the breaking up of the continents important to the dinosaurs?

Before the landmasses broke apart, land animals and plants of the time could spread more widely and may have been distributed over large areas. This is in part because there were no sea barriers to stop the spread of species.

However, during the Cretaceous Period when other parts of Gondwana began to break away, dinosaurs in Australia became more isolated and were able to develop differently from dinosaurs on other landmasses. As a result, Australian dinosaurs are different from dinosaurs found in other parts of the world.

What happened at the end of the Cretaceous Period?

All of the dinosaurs became extinct. During the same period, a very large number of the other animals and plants on Earth also died out, although some species survived and flourished.

What caused this extinction?

No one knows for certain. There are many theories, but some scientists believe that the extinction was caused by a changing climate that was the result of a large meteorite or comet colliding with Earth in what is now Mexico. This impact would have happened at extreme speed, and may have created a huge dust cloud blocking much of the sunlight and suddenly changing the climate.

Other scientists believe the extinction was the result of a more gradual climate change. This change may have affected the environment in which the dinosaurs lived to an extent that they were no longer able to survive.

 

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