Ancient worm provides unexpected evolutionary link in our early history

Fossils of a creature that lived on the ocean floor 505 million years ago have been identified by scientists as those of a previously-unknown marine worm, now named as  Spartobranchus tenuis . This is a particularly exciting find because not only does this fossil provide a vital link between two strikingly different groups, but it also has a bearing on the early evolution of a major phylum - the deuterostomes. Simon Conway Morris The identification of curiously-shaped fossil of a marine worm found in Canada as a new species has pushed the record of the group to which it belongs back by 200 million years and helped to solve an evolutionary puzzle. They examined numerous specimens, some of which were collected more than a century ago and are now held in the Smithsonian Institution (Washington, DC), along with new material recently collected by the Royal Ontario Museum (Toronto). The newly-identified species comes from the Burgess Shale beds, located in Yoho National Park in the Rocky Mountains of British Columbia, an area that boasts one of the world's most important fossil-rich deposits. The fossil shows that the acorn worm group - members of which thrive today in fine sands and mud - was living 505 million years ago when the mountainside shale in which it was discovered was under the ocean. Named Spartobranchus tenuis , the species was previously unknown to science and its survival as a fossil is remarkable.