04 January 2013
Vol 339, Issue 6115

About The Cover

Cover image expansion

COVER Head of a juvenile Nile crocodile (Crocodylus niloticus). The irregular polygonal scales on the face and jaws of crocodiles are not controlled genetically. Instead, the patterns are generated through a self-organizational process in which the stiff skin cracks in a tensional stress field as the crocodile grows. See page 78. Photo: Michel C. Milinkovitch and Adrien Debry