Earliest animals flexed their muscles

A group of British and Canadian palaeontologists have found fossils that show the earliest evidence of animal locomotion.

The team from the University of Oxford and Memorial University of Newfoundland, found fossilised trails left by Ediacarans, an enigmatic assemblage of soft-bodied creatures that lived 30 million years before modern animals evolved.

The find, in 565 million-year-old rocks at Mistaken Point in Newfoundland, Canada, appears in the current issue of the journal Geology.

The discovery of 70 fossilised trails, each about 5 to 17 centimetres long, is comparable to the kinds of marks left in the sea floor by modern animals like sea anemones, the researchers say.

Although they can't pin the trails to a specific creature, the discovery shows at least some of the Ediacarans were mobile, and hence must have had muscles.

Similarities in the trails to the modern-day anemone Urticina suggest the organisms that left the fossil traces may have had a muscular 'foot', the researchers say.

"This is exciting because it is the first evidence that creatures from this early period of Earth's history had muscles to allow them to move around, enabling them to hunt for food or escape adverse local conditions and, importantly, indicating that they were probably animals," says University of Oxford PhD student Alex Liu.

The Ediacarans are the earliest complex organisms before the Cambrian 'explosion of life' which marked the development of modern complex life.

But debate continues over just exactly what the Ediacarans looked like, or even what they were.