The form of Cathaymyrus suggests that it was a cephalochordate, but not a vertebrate. Pikaia of the Burgess Shale is very similar. They belong to an ostracoderm of the Class Agnatha . No paired fins. Lamprey eels are modern representatives of the Class Agnatha.
Ostracoderms are the most ancient agnathan fish.
An armored head shield. No joint between the head and the body. A mouth consisting of a series of small plates. A body that is usually flattened dorso-ventrally. Eyes usually on the dorsal part of the head.