Figure 2.

A phylogeny of chordate evolution. (a) A phylogenetic tree depicting the likely relationships between chordates and other animals, timing of genome amplifications (solid circles), and origin of novel characteristics. Phyla are in capitals; Porifera includes sponges; Cnidaria includes jellyfish and hydra; Echinodermata includes sea stars and sea urchins and Hemichordata includes marine acorn worms. (b) Genome size (Mb) and (c) estimated gene number of sequenced animal genomes are represented by bars.