Kullmann, J. & Scheuch, J.: Wachstums-Änderungen in der Ontogenese
paläozoischer Ammonoideen. [Growth Changes in the Ontogeny of Paleozoic
Ammonoids.]--[Konstruktions-Morphologie Nr. 2.]
Lethaia, Vol. 3, pp. 397-412.  Oslo, October 15th, 1970.
 
Ontogenetic allometries (heterauxesis according to Huxley) of about 50 Carboniferous
 goniatite species from Germany, Spain and USA have been studied by
 means of geometrical measurements of shell cross sections.  They indicate changes
 of proportions during ontogeny between coiling spiral, umbilical spiral, and
 whorl width.  The allometry constants change suddenly at defined stages.  Thus
 the ontogenetic growth pattern is polyphase, each phase being determined by
 a different allometric formula.