Upright-walking reptiles quickly replaced their predecessors
Reptiles learned to walk upright much more quickly than was originally thought, new research has shown.
The development was originally considered a slow process, taking between 20 and 30 million years.
But new research at Bristol University shows reptiles began walking with their legs tucked underneath their bodies, like modern mammals, much earlier.
This probably occurred shortly after a mass extinction, which occurred 250 million years ago, academics said.
Professor Mike Benton of the university said: "Dinosaurs, and later the mammals, owe their success to being upright. An upright animal, like an elephant or a diplodocus, can be very large because its weight passes directly through the pillar-like legs to the ground.
"Another advantage is that other upright animals, such as monkeys, can use their arms for climbing or gathering food."
Upright walking was a key component in the evolutionary success of the dinosaurs, which originated 25 million years after the mass extinction.
Newly-found footprint evidence suggests upright-walking reptiles quickly replaced the sprawling reptiles of previous epochs, rather than the two groups competing to cohabit the earth.
The results have been published in the Journal of Palaeontology.