The another are differentiated from the anamniotes by the presence of their terrestrially adapted eggs. These eggs are protected by amniotic membranes. Development of these membranes have provided another with their own aquatic environment needed for development.
The development of amniotic membrane is a characteric of amniotic eggs. These membranes include: chorion' facilitating the exchange of gases between the embryo and the mother; amnion, protection the embryo from injuries and shock and also aiding hydration; allantois, excretion of nitrogenous waste such as urea and uric acid etc and also help in respiration.
Another characteristics is waterproof skin due to the presence of lipids.
Another is the existence of costal rib ventilation of the lungs: enables of loss of CO2 through the lungs rather than buccal pumping as foumd in anamniotes.
