title: From snout to beak: the loss of teeth in birds.
abstract: All living birds are toothless, constituting by far the most diverse toothless vertebrate clade, and are striking examples of evolutionary success following tooth loss. In recent years, an unprecedented number of Mesozoic birds have been described, illustrating the evolution of dentition reductions. Simultaneously, major advances in experimental embryology have yielded new results concerning avian edentulism. Reviewing these lines of evidence, we propose hypotheses for its causes, with a prominent role for the horny beak during development. A horny beak and a muscular gizzard functionally 'replaced' dentition for food acquisition and processing, respectively. Together with edentulism itself, these features and others contributed to the later success of birds, as a result of their high performance or additional functionality working in concert in these complex organisms.
authors: Institut de Génomique Fonctionnelle de Lyon, CNRS, UMR 5242, ENS de Lyon, Université de Lyon, Université Lyon 1, Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France. antoine.louchart@ens-lyon.fr
authors: Antoine
authors: A
authors: Louchart
authors: Laurent
authors: L
authors: Viriot
mesh_terms: D000818:Animals; D001502:Beak / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology*; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology* / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D005580:Fossils; D018507:Gene Expression Regulation, Developmental; D005895:Gizzard, Avian / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology*; D008954:Models, Biological; D009805:Odontogenesis; D010802:Phylogeny; D012641:Selection, Genetic; D014070:Tooth / Q000033:anatomy & histology / Q000196:embryology / Q000502:physiology