title: Amphioxus and tunicates as evolutionary model systems.
abstract: One important question in evolutionary biology concerns the origin of vertebrates from invertebrates. The current consensus is that the proximate ancestor of vertebrates was an invertebrate chordate. Today, the invertebrate chordates comprise cephalochordates (amphioxus) and tunicates (each a subphylum in the phylum Chordata, which also includes the vertebrate subphylum). It was widely accepted that, within the chordates, tunicates represent the sister group of a clade of cephalochordates plus vertebrates. However, recent studies suggest that the evolutionary positions of tunicates and cephalochordates should be reversed, the implications of which are considered here. We also review the two major groups of invertebrate chordates and compare relative advantages (and disadvantages) of each as model systems for elucidating the origin of the vertebrates.
authors.affiliation: Laboratoire de Biologie Moléculaire de la Cellule, CNRS-UMR5161, INRA LA 1237, IFR 128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Schubert
authors.forename: Hector
authors.initials: H
authors.lastname: Escriva
authors.forename: José
authors.initials: J
authors.lastname: Xavier-Neto
authors.forename: Vincent
authors.initials: V
authors.lastname: Laudet
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D005580:Fossils; D008954:Models, Biological; D010802:Phylogeny