What are the common signs and differences in the structure of the integuments of birds and reptiles

What are the common signs and differences in the structure of the integuments of birds and reptiles, and what does this indicate?

Birds and reptiles actually have many common features in the structure of the skin: there are no (or practically absent) skin glands, respectively, the skin is dry; there are well-visible scales on the limbs; they have well-developed claws, the cover of the beak is also keratinized. The differences are justified by the conditions of various habitats: for birds, a characteristic feature is the presence of feathers, the body of a reptile is completely covered with scales. It should also be noted that the feathers and scales of reptiles initially develop from the rudiments of the epithelium (we take this as a sign of the same origin). Hence the conclusion – they most likely had a common ancestor.