Abstract: The expansion rates of the whorl spiral, the whorl cross section surface, the whorl
  height, and the whorl width of a series of Palaeozoic ammonoids were computed.  According to
  these expansion rates, differences between the major ammonoid groups can be recognised.  The
  suborders Agoniatitina, Gephuroceratina, and Paraceltitina as well as the order Prolecanitida show
  intense changes in and produce high expansion rates, whereas the representatives of the
  suborders Anarcestina, Pharciceratina, Tornoceratina, as well as Goniatitina usually produce low
  expansion rates.  The order Clymeniida displays a rather indifferent picture, but the expansion
  rates are usually rather low.