View source for FIXED REFERENCE MODELS

The first formal model was presented just over three decades ago by Berger (1969) who created the first theoretical morphospace of foraminifera. This morphospace was based on three parameters (Fig. 2): 
: (1) [q-ratio] — the ratio between successive chamber radii (Ri);
: (2) [a-angle] — ’angle of advance’ which is the angle between the lines connecting the center of the shell with two successive chamber midpoints;
: (3) [o-lap] — ’amount of overlap’ between two successive chambers, which is used to calculate a distance between centers of these two chambers, i.e., d=Ri/[o-lap]. 
In the model, the shell is fixed to a point that defines the center of the shell. The model represents a simple step-by-step rotation of a circle with a certain amount of overlap and expansion of circle radius (Ri). This model simulates isometric growth (all three parameters are held constant through ontogeny) and is confined to planispiral shells composed of circular chambers