HOW CAN A TUNICATE, A HAGFISH, AND A SEA OTTER BELONG IN THE SAME PHYLUM?
Notochord– Dorsal, rod-line skeletal structure found during the embryonic stage of development for most adult vertebrates; some non-vertebrates hold onto the notochord in some form
Hollow Nerve Cord-can become the spinal cord for some organisms
Post-anal tail– some only have one during embryonic development (like humans!)
Pharyngeal pounches -can develop into gills (fish) or straining device (tunicates) or in humans-the lower jaw, middle ear bones, rings of the trachea