The Cambrian fossil record indicates that most animal phyla had diversified and inhabited the Earth's oceans approximately 518 million years ago. But even though chordates—the group that includes ...

Add Yahoo as a preferred source to see more of our stories on Google. An extinct ribbonlike sea creature about the size of a human thumb was one of the earliest animals to evolve a precursor of a ...

The Middle Cambrian chordate known as Pikaia gracilens was once thought to be humanity’s earliest known ancestor, and the earliest known member of the phylum Chordata. Now, a new study flips this ...