Figure 1.

Phylogenetic relationships between the chordates, with emphasis on the tunicate clade (based on Kocot et al. 2018 and Delsuc et al. 2018). Tunicates and vertebrates share a more recent common ancestor than either do with cephalochordates. Because larvaceans (Appendicularia) are basal in the Tunicata, the ancestral tunicate may have been pelagic. The Ascidiacea are revealed to be paraphyletic due to the placement of the Thaliacea as sister to Phlebobranchia/Aplousiobranchia. Branch lengths are not to scale.