FIG. 44.5 A simple phylogenetic tree of bilaterian animals. Bilaterian animals can be divided into two major groups, the deuterostomes and protostomes. Protostomes can be further subdivided into lophotrochozoans and ecdysozoans.
Photo sources: (top to bottom) Glenn Nagel/iSockphoto; Lal/Getty Images; Franco Banfi/WaterF/age fotostock.