The Pores
Some pores were hard to identify in the external images of the eggshells because a “cap” made from the same mineral as the cuticle (Figure 5) covered them. Apteryx eggshells had cylindrical (or funnel shaped) pores that usually crossed the thickness of the eggshell slightly on an angle. In each fragment, very few pores reached the cuticle surface of the eggshell, with most reaching only half or less of the total thickness of the eggshell and many smaller pores that barely went beyond the mammillary layer (occluded pores, Figure 5A).
The observations made using the micro CT were confirmed by Scanning Electron Microscopy images of the exterior of the eggshells, where in some cases caps were seen covering the pores and in others mineral occlusions were observable (Figure 6). These caps and occlusions were observed in all four species and in all individuals.
Accordingly, fewer pores were visible at the cuticle side of the egg and many more from the inside. Since the CT is an X-ray technique, it is possible to see at different “depths” through the eggshell. When observed near the cuticle few pores were discernible but when looking at midway between the cuticle and the mammillae more pores become visible, confirming what was seen in the cross sections (Figure 6D, E).