Figure 1. Phylogenetic relationship among the non-bilaterians phyla and their respective subclasses. Dashed lines indicate uncertain locations of the branches. Many of the orders of Ctenophora are not monophyletic (Cyd* = Cydippida). Solid arrow points to phylogenetic position of M. leidyi and dashed arrow points to the phylogenetic position of P. pileus. See ‘Phylogenetic relationship of non-bilaterian animals’ for references.