Schematic model for regionalization and differentiation of the ventral mesoderm and the lateral plate mesoderm (LPM) in (a) amphioxus, (b) lampreys and (c) gnathostomes. Yellow, orange, green and blue bars represent the distribution of molecular markers for the ventral mesoderm/LPM (AmphiHand, LjHandA, Hand1, Hand2), the pharyngeal mesoderm (ph) and ALPM (AmphiNkx2-tin, AmphiTbx20, LjTbx20, Nkx2.5, Tbx20), the PLPM (LjMyb, cMyb), and the pharyngeal mesoderm (AmphiTbx1/10, LjTbx1/10, Tbx10), respectively. Pink bars represent the distribution of Irx3 orthologs (BfIrxC, Irx1/3, Irx3), which are expressed in the somatic layers of the LPM. vmp, ventral mesoderm posterior to the pharynx. See text for gene expression references. Modified after [4,38]