Victoria, Australia - On the ancient supercontinent of Gondwana 350 million years ago, a reptile pressed its small claws into the rain-damp ground. Its tracks now show the oldest-known vertebrate to have abandoned the oceans for dry land, a new scientific study suggests.

It also significantly pushes back the date for when these four-limbed pioneers made this important evolutionary step that would eventually lead to humans conquering the globe.

The tracks were found by amateur archaeologists on a 30-centimeter-wide sandstone slab in a mountainous area of the southeastern Australian state of Victoria.

First, there was a single footprint of an unknown animal which had "raindrop pockmarks all over it," said Per Ahlberg, a paleontologist at Sweden's Uppsala University.

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This suggests it was made before the brief shower, said the senior author of a new Nature study describing the discovery.

Then there were two sets of tracks from after the rain.

The second set of tracks suggests this reptile ancestor "was in more of a hurry," he added.

"You see the claws making long scratches on the ground."

But why are scientists so excited about the discovery?

The researchers cannot determine whether both sets of tracks were made by the same individual animal, but Ahlberg thinks this is unlikely.

The animal was 60-80 centimeters long and would have looked "quite lizard-like," he added.

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.

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Its ancestor tetrapods – notable for their four limbs – split into two groups, amniotes and amphibians.

While amphibians had to return to water to lay their eggs, amniotes evolved to have eggs strong enough to survive on land, shedding their last connection to water life.

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

This suggests the "water-to-land-dwelling transition" may have taken place in just 50 million years, much quicker than had been believed, Stuart Sumida of California State University commented in Nature.

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

"The only way to ever understand it is to look through these tiny little keyholes that we find into this strange, dark, lost world," Ahlberg said.