title: Morphomechanics and Developmental Constraints in the Evolution of Ammonites Shell Form.
abstract: The idea that physical processes involved in biological development underlie morphogenetic rules and channel morphological evolution has been central to the rise of evolutionary developmental biology. Here, we explore this idea in the context of seashell morphogenesis. We show that a morphomechanical model predicts the effects of variations in shell shape on the ornamental pattern in ammonites, a now extinct group of cephalopods with external chambered shell. Our model shows that several seemingly unrelated characteristics of synchronous, ontogenetic, intraspecific, and evolutionary variations in ornamental patterns among various ammonite species may all be understood from the fact that the mechanical forces underlying the oscillatory behavior of the shell secreting system scale with the cross-sectional curvature of the shell aperture. This simple morphogenetic rule, emerging from biophysical interactions during shell formation, introduced a non-random component in the production of phenotypic variation and channeled the morphological evolution of ammonites over millions of years. As such, it provides a paradigm for the concept of "developmental constraints."
authors.affiliation: Mathematical Institute, University of Oxford, Oxford, UK.
authors.forename: Alexander
authors.initials: A
authors.lastname: Erlich
authors.affiliation: Mathematical Institute, University of Oxford, Oxford, UK.
authors.forename: Derek E
authors.initials: DE
authors.lastname: Moulton
authors.affiliation: Mathematical Institute, University of Oxford, Oxford, UK.
authors.forename: Alain
authors.initials: A
authors.lastname: Goriely
authors.affiliation: Université Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, Villeurbanne Cedex, France.
authors.forename: Regis
authors.initials: R
authors.lastname: Chirat
mesh_terms: D060105:Animal Shells / Q000033:anatomy & histology / Q000254:growth & development*; D000818:Animals; D005075:Biological Evolution; D049830:Cephalopoda / Q000033:anatomy & histology / Q000254:growth & development*; D005580:Fossils; D055595:Mechanical Phenomena; D008954:Models, Biological; D009024:Morphogenesis