The Suborder Cephalaspida, commonly known as jawless fish, is a group of ancient fish that lived during the Silurian and Devonian periods. These fish were characterized by their lack of jaws and their bony plates that covered their heads and bodies. They were predators that fed on smaller organisms, and some even had the ability to burrow into the sediment to hide from predators. There are several synonyms for the Suborder Cephalaspida, including the Agnatha, Cyclostomata, and Lampreys. These synonyms reflect the different classifications and names that have been given to this group of fish over time. Regardless of their name, the Suborder Cephalaspida remains an important part of our understanding of the evolution of fish and marine life.