craniate, vertebrate - animals having a bony or cartilaginous skeleton with a segmented spinal column and a large brain enclosed in a skull or cranium

agnathan, jawless fish, jawless vertebrate - eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms

placoderm - fishlike vertebrate with bony plates on head and upper body; dominant in seas and rivers during the Devonian; considered the earliest vertebrate with jaws

flipper - the flat broad limb of aquatic animals specialized for swimming

fish - any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills; "the shark is a large fish"; "in the livingroom there was a tank of colorful fish"