Models for the morphology and morphogenesis of the ammonoid shell

Abstract

<p>The process of accretionary growth in molluscs is examined and a new growth equation suitable for accretionary growth is proposed and derived. The morphology of the shell in the Ammonoidea (Mollusca, Cephalopoda) is described and the morphogenesis simulated by means of theoretical models. In the case of the characterization of morphology, the shell is described by a set of objective descriptors that can be used in taxonomy. The morphogenesis of the ammonoid shell is explained in terms of static equilibrium of the secreting mantle and a diffusive process that mediates the actual precipitation of shell material on the growing edge of the shell. Different morphologies arise from varying the boundary conditions in the resulting differential equations.</p>