 A tunicate is a marine invertebrate animal , a member of the subphylum Tunicata , which is part of the Chordata , a phylum which includes all animals with dorsal nerve cords and notochords . The subphylum was at one time called Urochordata , and the term urochordates is still sometimes used for these animals . Some tunicates live as solitary individuals , but most are colonial . The colonial forms include both tholobates (colonies of individual animals) and lecithotrophic tholobates (colonies of eggs). The name tunicate is from the Latin tunica, meaning "tunic," a reference to the tunic-like covering of