Supplementary Figure 4

Histograms showing (A) the distribution of maximum size (maximum dm) and associated distributions of (B) whorl height index WHI, (C) umbilical width index UWI, (D) whorl interspace index WII, and (E) ribs per half-whorl RDW for all specimens of Group II (“Erbenoceras”). The two peaks at the 70-75 mm bin (falls in the 1.7-1.8 logarithmic size class) and the 90-95 mm bin (falls in the 1.9-2.0 logarithmic size class) are highlighted in black and grey respectively. Note, that there is no clear separation in frequency distribution of the conch or rib spacing parameters at these diameters, which are highlighted in the same colors. The bimodal distribution of the whorl height index WHI probably results from a sampling bias as this peak disappears when all measurements through ontogeny of more complete specimens are also plotted.