Figure 1. The ascidian Ciona. (a) Cutaway diagram of adult. (b) Transverse section through adult to show the pharynx surrounded at left, right and dorsally by the atrium, the endostyle in the mid-ventral line of the pharynx and the dorsal languets hooked ventralwards and to the right (in the diagram the right side of the animal is on the right). (c) Tadpole larva in right anterodorsal view. Note the clear distinction between head and tail, and the adhesive papillae for attachment to a substrate.

Figure 2. Pelagic urochordates. (a) The appendicularian Oikopleura inside its house. The animal is tadpole-like and beating of the tail pulls water through the house, filtering out plankton. (b) The doliolid Doliolum seen from the left.

Figure 3. The Ordovician mitrate Anatifopsis. (a) Dorsal view to show the atrial openings on the dorsal surface of the head as in a tunicate tadpole. (b) Left view to show tail, head and the dorsal atrial openings. The animal would have locomoted by pushing the tail forwards in the mud, so pulling the head rearward.