PATTERNS OF SHELL SHAPE AND CONTROL OF SIZE IN MESOZOIC AMMONITES
Main morphospace of the ADA-model
Equation of state of the ADA model
Main morphospace of the ADA-model described by the equations in the upper-right panel.
Moving the mouse over the black dots the local morphotype is shown with its associated parameters of shape and size.
The bold broken curve represents the main trend described by H2/D = 0.3 (plotted in the graph below left).
Two sizes (D) for each morphotype are shown for comparison, considering 5 and 10 whorls (Nw) from the end
of the protoconch onwards (protoconch diameter Dpro fixed as 0.45 mm). W/D estimated from the empirical
law W/D = 1.5 - 1.5(H2/H1) for coiled and W/D = 0.18 for uncoiled represented in the graph below rigth.
Plot of 1222 individual measurements of H2/D versus D.
The relatively low variation (CV% = 20%) around the mean value 0.3 is the leading evidence for a main trend shown in the top left graph of the morphospace.
Law of covariation. Relationship between relative whorl section width respect to involution measured by H2/H1.
Coiling involution seems to determine the relative whorl section width W/D.