Fig. 7

From quasi order to order, or disorder. Proposed trajectory of pore periodicity evolution in diatom girdle bands. The emergence of square lattice types appears to have occurred relatively early within the Coscinodiscophyceae, stemming from quasi-square lattice symmetries, as observed in extant species. Subsequently, hexagonal types arose from square lattice types. Both square and hexagonal types are reminiscent of sPhCs, while quasi-symmetries are quasi-photonic. Once established within a taxonomic lineage, square and hexagonal types appear to become irreversible traits. An exception exists within the Trieres family, where hexagonal types may partly exhibit quasi-hexagonal characteristics, potentially transitioning back to either square, or towards disordered types in some species. Unordered and pore less types similarly appear to persist as irreversible traits, once established. Boxes around the shapes indicate whether a structure is considered a sPhC (orange), quasi-photonic (yellow), single pore line (black), disordered (grey), or poreless (grey), following the definition developed in this study.