Humble arthropod beginnings

摘要

The most primitive member of the arthropods, which include spiders, insects and crabs, might have evolved a jointed exoskeleton initially as an adaptation for swimming. David Legg at Imperial College London and his colleagues studied Nereocaris exilis (pictured), which was discovered in the Burgess Shale, a rich fossil field in Canada. The creature is the most primitive arthropod yet found and dates back to the Cambrian period around 500 million years ago, the researchers say.