Have we misunderstood the first known animal? Dickinsonia , a weird organism from half a billion years ago, may have inflated its body to feed. The strategy is not seen in animals today, which raises questions about whether Dickinsonia really belongs in the animal kingdom after all.

Dickinsonia is one of a bunch of enigmatic organisms called the Ediacarans that lived a few tens of millions of years before familiar animals like sponges began forming fossils .

The Ediacarans have sometimes been interpreted as a failed evolutionary …