Vertebrates are found in the phylum Chordata. The subphylum that vertebrates belong to is called Vertebrata. Chordates are animals that possessed a notochord, a nerve cord, a tail and pharyngeal gill slits at some time during their lives.
The phylum Chordata were found in the Cambrian age about 525 million years ago. This phylum includes lancelets, tunicates, lampreys, sharks, bony fishes, amphibians, reptiles, birds and mammals.
A notochord is a rod that lies along the backs of embryos and some adult chordate species. The hollow nerve cord lies next to the notochord. Many of these chordate features appear only in the embryos of certain species and are lost when the organisms mature.