The cuticle (or external layer)
All Apteryx species presented thin cuticles with a wax-like appearance, which in contrast to the smooth sponge like texture of the crystalline layer made it easy to identify (Figure 2A). Seen from outside the cuticle was smooth and unpigmented, pores seemed to radiate from underneath the cuticle (Figure 2B).
The cuticle thickness decreased significantly with latitude, being thicker in Brown Kiwi and thinnest in Rowi and Tokoeka; the significance was due to differences between Brown Kiwi and Rowi (Table 3). Under the micro CT scan, the crystalline structure of the cuticle became apparent, and it was possible to discern the individual crystals that formed it (Figure 4).