What it was
A long, narrow body up to 27 centimeters long, built from about fifty segments. It comes from rock about 550 million years old in southern China, where 35 bodies and 13 trails have been found.
Why it matters
One Yilingia lies dead at the end of its own trail, 58 centimeters long. A trail alone tells you little. A trail with the animal still at the end of it tells you what made the tracks: something that moved in a chosen direction.