Cretaceous, Folkestone, England
The complex suture line visible in this eroded specimen joins successive plates of the ammonite's shell as it grows. (Sutures are not visible in whole specimens because they are covered by the shell's surface ornamentation.) The pattern seems similar at different scales, perhaps to provide strength which might be compromised by a straight suture line. Such patterns are reminiscent of the fractals generated mathematically by Benoit Mandelbrot.