When did dinosaurs live? (2024)

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Non-bird dinosaurs livedbetween about 245 and 66 million years ago, in a time known as the Mesozoic Era. This was many millions of years before the first modern humans,hom*o sapiens, appeared.

Scientists divide the Mesozoic Era into three periods: theTriassic, Jurassic and Cretaceous. During this era, the land gradually split from one huge supercontinent into smaller ones. The associated changes in the climate and vegetation affected how dinosaurs evolved.

Triassic Period (252 to 201 million years ago)

All continents during the Triassic Period were part of asingle land mass called Pangaea. This meant that differences between animals or plants found in different areas were minor.

The Triassic climate was relativelyhot and dry, and much of the land was covered withlarge deserts. Unlike today, there wereno polar ice caps.

It was in this environment that the reptiles known asdinosaurs first evolved. Reptiles tend to flourish in hot climates because their skin is less porous than, for example, mammal skin, so it loses less water in the heat. Reptile kidneys are also better at conserving water.

Toward the end of the Triassic, a series ofearthquakes and massive volcanic eruptionscaused Pangaea to slowly begin to break into two. This was thebirth of the North Atlantic Ocean.

Jurassic Period (201 to 145 million years ago)

At the end of the Triassic Period there was amass extinction, the causes of which are still hotly debated. Many large land animals were wiped out but thedinosaurs survived, giving them the opportunity to evolve into a wide variety of forms and increase in number.

During the Jurassic Period, the single land mass,Pangaea, split into two, creating Laurasia in the north and Gondwana in the south. Despite this separation, similarities in their fossil records show that there were some land connections between the two continents early in the Jurassic. These regions became more distinct later in the period.

Temperatures fell slightly, although it was still warmer than today due to higher amounts of carbon dioxide in the atmosphere.Rainfall increasedas a result of the large seas appearing between the land masses.

These changesallowed plants such as ferns and horsetails to grow over huge areas. Some of this vegetation became the fossil fuels that we mine today. Elsewhere there wereforests of tall conifer treessuch as sequoias and monkey puzzles.

Cretaceous Period (145 to 66 million years ago)

During the Cretaceous theland separated further into some of the continents we recognise today, although in different positions. This meant that dinosaurs evolved independently in different parts of the world, becomingmore diverse.

Sauropods reached their largest sizes in the Cretaceous. The biggest were the titanosaurs. Patagotitan was a staggering 37.5 metres long!

Other groups of organisms also diversified. The first snakes evolved during this time, and by the end of the Cretaceous, flowering plants were a much more common part of Earth's plant life.

Variousinsect groups also appeared, including bees, which helped increase the spread of flowering plants. And mammals now included tree climbers, ground dwellers and even predators of small dinosaurs.

Did you know?

Sea levels rose and fellrepeatedly during the Cretaceous Period. At the highest point there were many shallow seas separating parts of the continents we know today. For example, Europe was made up of many smaller islands. Thick layers of sediment built up at the bottom of these seas assingle-celled algaedied and theirskeletons fell to the seabed.

This is how most of thechalkwe use today was first formed. So much so, that 'Cretaceous' comes from the Latin word for chalk,'creta'.

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