Figure 2.

Crystal architecture of the skeleton wall. Inverse pole figure (IPF) map across the corallite wall of L. pertusa corresponding to the area displayed in Fig. 1d. The map shows the distribution of aragonite crystallographic axes with respect to the radial growth direction R of the corallite. The dominant bluish colour in the external part of the corallite wall (i.e. the TD area located in the lower half of the map) indicates that aragonite [001] axes are preferentially oriented parallel to R (within a tolerance of ~±45°), i.e. normal to the corallite margin. The crystallites coloured in reddish and greenish are those for which the axes close to R are [010] and [100], respectively, i.e. those intersecting the acquisition surface at high angles. A distinctive feature of the internal part of the corallite wall (upper half of the map) is the RAD lamella from which aragonite needles are radiating along their [001] axes. RADs appear black because they did not produce any diffraction pattern, possibly because of poor crystallinity and/or small crystal size. Optically opaque bands identified in Fig. 1d have been superimposed in light grey and delimited by dashed lines. R and L as in Fig. 1.