FIGURE 7 in Hornera currieae n. sp. (Cyclostomatida: Horneridae): a new bathyal cyclostome bryozoan with reproductively induced skeletal plasticity

FIGURE 7. Crystallographic orientation of Hornera currieae n. sp. skeletal walls. A. EBSD map of calcite from a polished longitudinal-tangential section of a mid-colony branch bifurcation, grain boundaries demarcated by black lines (inset, imaged section relative to branch axis). B. Crystallite orientation frequency distribution for entire map. C. Pole figures for c-, a- and m-axes; color ramp in all cases indicates the orientation of the crystalline c-axes relative to the sectional plane. Crystallites at edges of EBSD map lie at approximately 60°–70° to the sectional plane, grading to ~0°–15° inclination (i.e., roughly wallparallel) along midline region; note, the plane of the polished section is probably inclined ~10° from the wall surface in the longitudinal axis, hence rarity of crystallites indexed at 0° inclination. The pole figures are equal area projections; each shows orientations of 29,274 indexed crystallites displayed at 1 point per grain (upper hemisphere projection). The broad swathe of c-axes in the pole figure reflects the cylinder-wrapping orientation of indexed crystallites. The map and pole figures indicate c-axes are consistently near-perpendicular to skeletal wall surfaces, whereas a-axes and m-axes are scattered randomly around the corresponding c-axes. The crystallite indexing rate drops rapidly towards the edges of the section due to the increasingly thin (~200 nm) profiles of exposed laminae oriented at low angles to the EBSD detector. Scale bar: 100 µm.