Abstrat: There are fundamental differences in the qualitative shell characteristics as well as in the mode
 of ontogenetic conch development in Paleozoic ammonoids.  Devonian forms exhibit monophasic and
 diphasic growth patterns; with the beginning of the Carboniferous triphasic growth patterns appear
 becoming predominant in the Upper Carboniferous.  The Permian goniatites show the widest range of
 shell diversity among Paleozoic ammonoids.