SA MUSEUM scientists and naturalist Sir David Attenborough have found what may be a "new" species in the Flinders Ranges.

They made the fossil discovery while filming with Sir David Attenborough.

It's a strange soft-bodied animal from the ediacaran period (550 million years ago), when primitive animals first moved around on the sea floor.

Sir David reflects on the moment of discovery in the documentary Attenborough's Journey, the making of his new two-part series First Life.

He had travelled to the Flinders Ranges to watch the palaeontologists at work, turning slabs of rock in the hope of finding something new.

"There is a great thrill of being alongside these people who know what they're doing, what they're looking for and how to look for it," he said.

"Of course you naively think it would be wonderful to go along and they may be able to turn over a rock and say, `A-ha, this is a new species'. Looking for fossils is not like that, except that it actually happened."

Sir David visited teams of scientists all over the world in the filming of First Life, from the fog-bound coastline of Newfoundland to the deserts of North Africa and the rainforests of Queensland, but the Flinders Ranges of South Australia was a highlight.

Palaeontologist Dr Jim Gehling says the Ediacara fossils of the Flinders Ranges "show an enormous range of body shapes and sizes, and evidence of many very different lifestyles".

Some lived in very shallow marine environments, and others in much deeper water.

"We have the first animals that had sex and the first animals with heads and tails," Dr Gehling said.

"They could move and they could feed on the sea floor, rather than just sit there like sponges and waiting for the food to come to them."

The first animals with heads and segmented bodies were discovered at Ediacara Conservation Park on the western margins of the Flinders Ranges by the late Dr Reg Sprigg in 1946.

Palaeontologists at the SA Museum led by Dr Gehling and Professor Mary Droser from the University of California, Riverside, have discovered complex traces in these Ediacaran sea floors that show how the animals moved and fed.

First Life begins on Sunday at 7.30pm on ABC1.