The Rise and Fall of the Dinosaurs

In the popular imagination, the dinosaurs' rule over the Earth lasted from the first stirrings of life on the planet right up until their extinction.

But, of course, dinosaurs weren’t the first inhabitants of Earth.

It was around 390 million years ago that life first crawled onto land. From then until the end of the Permian Period, around 252 million years ago, the animal kingdom comprised a range of strange reptilian and mammalian creatures.

The Permian Period, however, ended with the largest mass extinction event in Earth’s history.

It began when volcanoes started exuding vast amounts of magma. It continued to flow for several hundred thousand years, perhaps even a few million. There’s evidence of the scale of the disaster from geological records; when looking at formations from this period, the rock type changes dramatically and fossils simply stop appearing.

It was devastating: around 90 percent of all species had died out by the time the crisis ended and ushered in the Triassic Period.

However, not all life vanished. Tracks from early archosaurs – the early reptilian ancestors of dinosaurs – have survived from around 250 million years ago.

These archosaurs thrived in this new world, and soon divided into two groups. There were the ancestors of our modern crocodiles, the pseudosuchians – their name means "false crocodiles” – and the avemetatarsalians.

It was these avemetatarsalians that evolved into dinosaurs, who then split into three groups. There were the meat-eating theropods, the plant-eating ornithischians and the long-necked sauropods.

These groups didn’t just evolve and survive – they thrived.

For instance, 230 million years ago, in what is now Argentina’s Ischigualasto Provincial Park, numerous species established themselves. We know this because of the phenomenal quantity of fossils that have been found there over the course of the twentieth century. The hot and humid climate there, which led to occasional flooding, was ideal for preserving fossils.

So, it had taken a near apocalypse to for the dinosaur age to begin, but the Triassic Age had now truly dawned. It was to be a fascinating and diverse evolutionary journey – yet there was still quite a long way to go.