Fig. 6.

Morphology variety for (symmetric) interlocking bivalved shells and sample shells illustrating the diversity of form (brachiopod species from Upper Left to Lower Right: Cererithyris arkelli; Sphenorhynchia plicatella; Cererithyris intermedia; Kutchirhynchia obsoleta). The simulated shells correspond to the 4 different combinations of a low ($b=1$) and a high ($b=2$) coiling rate and small ($k=10$) and large ($k=500$) mechanical stiffness. The computational procedure is outlined in SI Appendix, section 4. (Scale bars: 10 mm.)