Fig. 4
From: Jurassic ammonite aptychi: functions and evolutionary implications
Stratigraphic ranges, phyletic relationships, aptychus types, and number of families in the Jurassic Ammonitina. Aptychi main evolutionary changes and occurrence of first lappeted microconchs (Hildoceras) indicated as explained in text. Phylogeny based on Donovan et al. (1981). Distribution of types of aptychus (Fig. 1) after Arkell (1957), Lehmann (1976), Schweigert (2000), Parent et al. (2014) and discussed in text. Minor subdivisions of each stage correspond to the zonal subdivision of Cariou and Hantzpergue 1997