Sea worm fossil gives clues to 'common ancestor'

Fossils of a sea worm that lived on the ocean floor about 500 million years ago are giving new insights into how early creatures evolved.

Tube-like structures once thought to be a type of seaweed were made by a worm that lived a solitary life on the sea bed, say scientists.

Prof Simon Conway Morris, from St John's College, University of Cambridge and a co-researcher on the study, said: "Now we know that they were primitive hemichordates - perhaps the most primitive of all."

"Through them, we can get clues about the anatomy and lifestyle of the last common ancestor that we all share, and this adds further evidence to the hypothesis that the ancestor was a filter-feeder like Oesia."

The specimens, found near Marble Canyon in the Canadian Rockies, are exceptionally well preserved, giving details of the animal's internal anatomy. They rival or are even better than the nearby Burgess Shale.