Crocodile Head Scales Are Not Developmental Units But Emerge from Physical Cracking

Abstract

How the Crocodile Got Its Scales Mammalian hairs, avian feathers, and reptile scales differentiate and grow from genetically controlled units. Using three-dimensional (3D) computer graphics and computational biology to study scale generation, Milinkovitch et al. (p. 78 , published online 29 November; see the cover) show that crocodilians' face and jaw scales do not follow this rule but emerge by physical cracking of the developing skin in a tension field. Thus, a crocodile's head scales are not genetically controlled developmental units but are random polygonal domains of keratinized skin that are generated from a self-organizing physical process.