Why can reptiles live in open places and not be afraid of the sun’s rays?

Reptiles arose when the Earth became drier, and therefore they have adaptive characteristics to such conditions:
their evaporation is greatly reduced due to the absence of skin glands;
not urea is released, but uric acid, which requires less water consumption;
have dry, more often scaly skin.
But reptiles, like all other animals, cannot stand too high a temperature.