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Home > Why did the dinosaurs die out? > The Rise of Mammals  

02. Why did the dinosaurs die out?


The K-T Extinction Event was not the biggest ever to occur and it probably won’t be the last. There have been six major and at least 12 minor extinction events during the past 650 million years of the Earth’s history.

The dinosaurs died out at the end of the Cretaceous period but mammals and the ancestors of modern birds survived. Mammals, frogs, turtles and crocodiles lived and survive to the present day. Perhaps they had the characteristics that suited them to the new environment.

Mammals are able to maintain their body temperature. They are less dependent on environmental temperatures, unlike ‘cold-blooded’ species such as reptiles. After the extinction of the dinosaurs, mammals were free to colonise cooler areas of the world and dominate the planet. This led to the Rise of Mammals.

Some evolved eventually to become extremely large and were referred to as Megafauna.

Examples include:

  • Diprotodon the largest marsupial currently known and likened to a giant wombat weighing between 1000 and 2000 kilograms
  • Species of giant kangaroo such as Procoptodon goliah

Many of these species became extinct during the last stage of the Pleistocene epoch, about 50,000 – 16,000 years ago.

Image of Diprotodon and Procoptodon

Diprotodon on left and Procoptodon on right.  Artist: Robert Allen, © Queensland Museum.