What aromorphoses have allowed reptiles to spread widely in terrestrial habitats?

1) Features of breathing – due to the appearance in the skeleton of the chest, which provides inhalation and exhalation. Breathing is only pulmonary. The lungs are of a complex, cellular structure with a larger respiratory surface than in amphibians.
2) Features of the structure of the integument – dry skin, covered with horny scales, which protects the body from drying out.
3) Features of reproduction – internal fertilization, large eggs, rich in nutrients
you and covered with a leathery membrane or shell that protects them from drying out, the appearance of fully formed reptiles from the eggs.
4) Features of the excretory system, which requires a negligible amount of water to isolate the products of nitrogen metabolism.
5) Features that provide a higher level of metabolism than in amphibians – More complete separation of arterial and venous blood flows, a three-chambered heart with an incomplete septum.
6) More perfect nervous system.