Pisciforma (hagfish and lampreys) - characterized by the absence of separate jaws and bone tissue in the skeleton. The body is naked, slimy, eel-like. The axial skeleton is formed by chordae. The mouth is funnel-shaped or round. Teeth horny. There is a powerful tongue armed with horny teeth or horny tooth plate. One unpaired nasal opening. Paired fins are absent. Respiratory organs - 5-16 pairs of gill sacs. The caudal fin is protocercal.
Low aquatic vertebrates; represented mainly by extinct forms. In the modern fauna, the rPisciforma include only Myxinae and Lampreys.