The age of the dinosaurs was triggered by climate change, new research has found.
It was rising temperatures rather than competition that allowed ancient reptiles to diversify, leading to the largest creatures to ever walk the Earth.
The phenomenon opened the door to the emergence of iconic plant eaters like Diplodocus and Brachiosaurus.
They were able to thrive and expand into new territories after global warming about 200 million years ago.
It followed a mysterious mass extinction linked to vast volcanic eruptions that plunged the world into cold and darkness.
Unable to cope, more than three-quarters of terrestrial and marine species were wiped out. They included large terrestrial vertebrates such as the giant armadillo-like etosaurs.
Early dinosaurs survived on thick blankets of feathers. Subsequently, they took advantage of this by moving from a minority group to those in charge.
The University of Birmingham team analyzed computer models of prehistoric global climate conditions such as temperature and rainfall with.
They compared them with data on the different locations of the dinosaurs taken from sources such as the Paleobiology Database.
He showed that the primitive sauropods with their long tails, necks and small heads were the meteoric achievement of a period of turbulent evolution.
The results have implications for today. Animals have already started changing shape to cope with weather-related stresses.
They develop larger ears, mouths and limbs to help regulate body temperature, biologists say.
Lead author Dr Emma Dunne, now at Friedrich-Alexander-University Erlangen-Nurnberg, Germany, said: “Instead of dinosaurs being overtaken by other large vertebrates, it was the variations of climatic conditions that restricted their diversity.
“But once those conditions changed across the Triassic-Jurassic border, they were able to thrive.
“The results were somewhat surprising, as it turns out that sauropods were really picky from the start. Later in their evolution, they continue to stay in warmer areas and avoid polar regions.
Dinosaurs began to appear around 230 million years ago. They became one of the most successful groups of animals – ruling the earth for 165 million years.
Co-author Professor Richard Butler said: “Climate change appears to have played a very important role in the evolution of early dinosaurs.
“What we want to do next is use the same techniques to understand the role of climate in the next 120 million years of dinosaur history.”
The study is in the journal Current Biology.