Chordata is the phylum of the vertebrates, but not all chordates are vertebrates. Vertebrata is the subphylum of chordata.
Marine vertebrates are vertebrates which live in a marine environment. These primarily include fish, seabirds, marine reptiles, and marine mammals. These animals have an internal skeleton and make up about 4% of the sea's animal population. Marine vertebrates include fish, reptiles,and mammals like Australian Fur Seal, Humpback Whales, and many more species of sea living creatures.
The following are the major marine classes of this subphylum:
Category.JawlessFish-Agnathans
Category.SharksRays-Chondrichthyes-Elasmobranchia
Category.BonyFish-Osteichthyes
Category.SeaTurtles-Reptilia
Category.WhalesSeals-Mammalia
