Cephalochordates are segmented marine animals that possess elongated bodies containing a notochord that extends the length of the body from head to tail. They are only a few centimeters in length and due to their lack of a mineralized skeleton, their presence in the fossil record is minimal. A few fossils have been found such as the Burgess Shale of British Columbia which contained the fossils of Pikaia, and the Yunnanozoon fossil which also dates back to the Cambrian period.
They are survived and represented today as lancelets. There are about 30 known species of lancelets. Lancelets are small, eel-like organisms that live in the ocean. They are filter feeders and use cilia to filter food out of the water. They anchor their tails in the sand and let the water wash over their mouths. They have a nerve cord, but no brain or vertebrae.