Evolution of Hard Proteins in the Sauropsid Integument in Relation to the Cornification of Skin Derivatives in Amniotes

The study examined the evolution of hard proteins, particularly beta-keratins, in the integument of sauropsids (reptiles and birds) and their relation to the cornification process in amniotes. It found that beta-keratins in reptiles and birds form fibrous polymers and filaments, differing from the amorphous keratin-associated proteins (KAPs) in mammals. The research highlighted the evolutionary divergence between lepidosaurian and chelonian/archosaurian proteins, noting that the latter group shares a common ancestor. The study suggested that feathers evolved from scales through specific mutations and structural modifications in keratins, emphasizing the need for further phylogenetic analysis and genome sequencing to fully understand the molecular evolution of these proteins.