||Alibardi L. Adaptation to the land: The skin of reptiles in comparison to that of amphibians and endotherm amniotes. J Exp Zool B Mol Dev Evol. 2003 Aug 15 298(1):12-41. DOI: 10.1002/jez.b.24 p.14 right column top paragraphPubMed ID12949767
||Pough FH, Andrews RM, Cadle JE, Crump ML, Savitzky AH, Wells KD. 2001. Herpetology, second edition. Upper Saddle River, NJ: Prentice Hall.
||P.14 right column top paragraph: "The mature tissue (epidermis) is covered by a dead stratum corneum that is almost impermeable to gases, so that the respiratory role of the amphibian epidermis is lost (Fox, ’86 Warburg et al., ’96). A fundamental step toward the adaptation of the integument to the terrestrial environment was made in the mid Carboniferous, about 340 million years ago by the basal amniotes (or advanced anthracosaurians, primary source), from which reptiles, birds, and mammals evolved."