Chordata devided into Acraniata and Craniata. Acraniata included urochordata and cephalochordata. Urochordata having notochord in tail in only larval condition and show retrogressive metamorphosis. Endostyle present in urochordata.e.g ascidia , salpa, herdmania etc.Cephalochordata having notochord till head region.They have myotomes.e.g amphioxus. Craniata included vertebrata.