From INTRODUCTION:

     The purpose of this paper is to discuss the late-ontogenetic shell
  modifications in ammonoids and any dimorphism or related phenomena that
  resulted.  However, the article definitely is not intended as an exhaustive
  reiteration of all that has been written about these subjects.  As Callomon
  (1981) wrote: "To review yet again the topic of dimorphism as a whole would
  be unnecessarily repetitive. . . ." lf one wished to undertake such a task,the
  works of Callomon, Makowski, and Westermann listed in the bibliography
  would be admirable places to start, with Lehmann (1981) thrown in for a more
  recent perspektive.
      At the outset, a few logistical remarks are appropriate.  This chapter is
  decidedly a committee effort.  Different parts of the geological column are  
  dealt with by different people: R. A. Davis compiled the Paleozoic part; H.  
  Bucher,the Triassic; J.-L. Dommergues and D. Marchand, the jurassic-, and N.
  H.Landman, the Cretaceous.  Everyone contributed ideas for the general, intro-
  ductory, and closing matter, but R. A. Davis bears the primary responsibility
  (? blame) for putting it into its present form.  An exception to this is Sec-
  tion 3.6, which is the work of J.-L. Dommergues and D. Marchand.
     Over the years, the, convention has built up that fossil cephalopods should
  be illustrated with their adapertural ends uppermost.  This convention, of
  course, flies in the face of the probable orientation of the animals in life,  
  at least for those in which the final body chamber is preserved.  We prefer
  an orientation that coincides with that in life, and most of the
  illustrations in this chapter reflect this.  Some of the illustrations that  
  were published previously,
  however, are oriented with the adapertural end uppermost, to be faithful to
  the original publications.