Horseshoe Crabs, Coelacanths, Seven-gilled sharks, hagfish. Throughout the oceans there are creatures whose primitive bodies hearken back to earlier days in our evolutionary history. They possess basal characteristics that are more akin to those of the ancestors of our contemporary phyla. Because we can look into these organisms and learn something about our own deep past, we think of them not as modern descendants, but as living fossils, relics of a primeval state.
This is, of course, a misnomer.