which clade is most primitive
Lampreys and hagfishes are the only jawless vertebrates to survive today. They both have a round mouth and for this reason are often referred to as cyclostomes. They are the most primitive of the vertebrates. By primitive, a biologist means that they are the least changed from the first vertebrates.1  They have no paired pectoral (shoulder) or pelvic (hip) fins. 2  Their notochord persists for life, never being completely replaced by a backbone even in the lampreys.3  They have no scales.y primitive, a biologist means that they are the least changed from the first vertebrates. 1  They have no paired pectoral (shoulder) or pelvic (hip) fins. 2  Their notochord persists for life, never being completely replaced by a backbone even in the lampreys. 3  They have no scales.