remarks on the evolution of the integumental scale armour

The physical appearance of pangolins is based on large, hardened, plate-like scales found dorsolaterally at the body and the tail, whereas the abdominal body part shows a thick soft stratum corneumand a dense cover of fine hairs.5 These scales, which are soft on newborn pangolins but harden as the animal matures, are formed by α-keratins and β-keratins,6,7 guaranteeing a high abrasive wear resistance.8 If curling up of the animal when threatened, the overlapping scales can act as armour because they are sharp and thus provide extra defense.6 In this context it is quite interesting that the water-to-land transition in the stem lineage of tetrapods was associated with a major radiation and functional diversification of keratin genes. These duplications acquired functions that serve rigidity in integumental hard structures and were the prime for subsequent independent keratin diversification in tetrapod lineages. 9