How do we know this is an animal?

On a cattle station in remote South Australia, sandstone slabs have eroded out of the Earth – revealing fossils from half a billion years ago. This alien-looking imprint captures Dickinsonia, a limbless, disc-like animal that rippled over the ancient sea floor. Other fossils at the site have revealed the oldest scavenging behaviour, the earliest movement through the water column and even the earliest documented sexual reproduction (which is less exciting than you might think – it’s a lot like how corals do it, releasing clouds of eggs and sperm). From fossils like these, palaeontologists are building a picture of a world at the dawn of animal evolution. Read more on page 56.