But that notochord was enough to hail this half-a-billion-year-old fossil a the beginning of the phylum Chordata. That’s why it came as quite a surprise when researchers from the University of ...

A fossil analysis suggests that the yunnanozoan ... but the point in time at which these animals branched away from the phylum of chordata, which lack the rigid structures that protect vertebrates’ ...

The earliest known primitive chordate is Pikaia gracilens, a wormlike creature that swam in middle Cambrian seas. Fossils found in the Burgess Shale of British Columbia show traces of a notochord ...