Introduction

Striking similarities between the molecular and genetic mechanisms that control development in very diverse animals are causing biologists to reassess hypotheses regarding the evolution of body plans, particularly in the light of the recent availability of whole genome sequence information for some species. This recent convergence of developmental and evolutionary analyses is the subject of this issue, addressed both at the level of morphology and molecular biology as well as emerging work on whole animal genomes. We wanted to assemble a volume that highlights some of the molecular advances made in genetically tractable systems including worms, zebrafish and ascidians, and also introduce some of the new genomic and theoretical approaches that may be less familiar to mainstream developmental biologists. The result is an edition that focuses primarily on brain evolution, axial patterning and vertebrate origins, biases that in part reflect our own specific interests.