A huge mouth and no anus – this could be our earliest known ancestor

Thought to have lived 540 million years ago, the discovery of Saccorhytus coronarious fossils sheds light on the early stages of evolution

You won't find it in your family album, but a tiny prehistoric creature with a bag-like body, a huge mouth and no anus has become the best candidate yet for our earliest known ancestor.

Thought to have lived as long as 540 million years ago, the creature is the oldest known member of a large group of animals known as deuterostomes, which includes vertebrates - such as humans - as well as starfish, sea urchins and a host of other fauna.