title: A developmental perspective: changes in the position of the blastopore during bilaterian evolution.
abstract: Progress in resolving the phylogenetic relationships among animals and the expansion of molecular developmental studies to a broader variety of organisms has provided important insights into the evolution of developmental programs. These new studies make it possible to reevaluate old hypotheses about the evolution of animal body plans and to elaborate new ones. Here, we review recent studies that shed light on the transition from a radially organized ancestor to the last common ancestor of the Bilateria ("Urbilaterian") and present an integrative hypothesis about plausible developmental scenarios for the evolution of complex multicellular animals.
authors.affiliation: Kewalo Marine Laboratory, PBRC, University of Hawaii, 41 Ahui Street, Honolulu, HI, 96813, USA. mqmartin@hawaii.edu
authors.forename: Mark Q
authors.initials: MQ
authors.lastname: Martindale
authors.forename: Andreas
authors.initials: A
authors.lastname: Hejnol
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D019070:Cell Lineage; D016764:Cell Polarity; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D005775:Gastrula / Q000378:metabolism*; D054262:Gastrulation; D010802:Phylogeny