After a brief shower in part of the ancient supercontinent Gondwana 350 million years ago, a reptile dug its tiny claws into the still-wet earth.

Its tracks, found in Australia, mean it is the oldest known vertebrate to have permanently left the oceans and crossed onto land, according to a study.

It also significantly shifts the date on which these four-legged pioneers took that important evolutionary step that eventually led to humans conquering the world.

The footprints were discovered by amateur archaeologists on a 30-centimeter slab of sandstone in a mountainous region in the southeastern Australian state of Victoria, AFP reports.

A single footprint from an unknown animal was initially discovered that had “raindrop marks,” said Per Ahlberg, a paleontologist at Sweden's Uppsala University.

That suggests it was made before the brief rain, said the senior author of the new Nature study describing the discovery.

Then there are two sets of traces from the time after the rain.

The second set of tracks suggests that this reptilian ancestor “was in more of a hurry, you see the claws making long scratches on the ground,” he explained.

Researchers can't determine whether the two sets of tracks were made by the same animal, but Ahlberg thinks that's unlikely.

The animal was 60-80 centimetres long and looked “quite lizard-like”, he pointed out.

That the animal had claws is a clear sign that it was an amniote, a group of animals that today includes mammals, birds and reptiles.

The ancestors of tetrapods, distinguished by their four limbs, are divided into two groups - amniotes and amphibians.

While amphibians had to return to the water to lay their eggs, amniotes evolved so that their eggs were healthy enough to survive on land by shedding their last connection to aquatic life.

The discovery suggests that amniotes existed 35 to 40 million years earlier than previously thought, during the transition between the Devonian and Carboniferous periods, the study said.

This suggests that the “transition from aquatic to terrestrial inhabitants” may have taken place in as little as 50 million years, much faster than previously thought, said Stuart Sumida of California State University.

It would be just the latest twist in the tale of how animals rose from the ocean to dominate the land.

“The only way to understand it is to peer through these little keyholes we find, into this strange, dark, lost world,” Ahlberg stressed. | BGNES