Animal ancestors 'outright weirdos': ANU

Our earliest animal ancestors were a "mix bag of outright weirdos", according to the latest research.

A report from The Australian National University (ANU) unearthed new clues on animals going back 575 million years by looking at what they last ate.

Scientist were able to extract and analyse natural chemical products contained in Ediacara bioata fossils - the world's oldest large organisms.

While the fossils in the study were retrieved in Russia, Ediacara biota fossils were first discovered in the Ediacara Hills in the South Australian Flinders Ranges.

These organisms lived 20 million years before the Cambrian Explosion - the most intense burst of evolution ever recorded.

"They are the origin of us and all animals that exist today. These creatures are our deepest visible roots," lead author Dr Ilya Bobrovskiy said.

Kimberella is one of two Ediacara biota organisms, the most advanced creature of the Ediacarans, whose last meals were examined.

The research confirmed the slug-like organism had a mouth and gut that digested food the same way humans do.

Scientists also found another animal, called Dickinsonia, absorbed food through its 1.4 metre long body.

The animal had no eyes, mouth or gut but instead a rib-like design on its body.

Co-author Professor Jochen Brocks said the energy-rich algae consumed by the Ediacara biota organisms may have been instrumental for its growth.

"This was a Eureka moment for us," Prof Brocks said.

"We can now make gut contents of animals visible even if the gut has since long decayed."

Prof Brocks said the difficult part was differentiating whether the decaying molecules are the creature itself or the bacterial remains in the gut.

Even for animals dead for millions of years, it appears the saying 'you are what you eat' rings true.