animal order - the order of animals

Agnatha, superclass Agnatha - superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys; hagfishes; some extinct forms

cyclostome - primitive aquatic vertebrate

Hyperoartia, Petromyzoniformes, suborder Hyperoartia, suborder Petromyzoniformes - lampreys as distinguished from hagfishes

family Petromyzontidae, Petromyzontidae - lampreys

Hyperotreta, Myxiniformes, Myxinoidea, Myxinoidei, suborder Hyperotreta, suborder Myxiniformes, suborder Myxinoidei - hagfishes as distinguished from lampreys

family Myxinidae, Myxinidae - slime-producing marine animals: hagfishes