What is the difference between the skin of animals living in cold regions and the skin of those living in hot regions?

Animals that live in extreme climates have physical characteristics that help them survive in harsh environments. Their skin, as well as their fur or feathers, serves as an insulator and thus acts as a natural barrier to the cold or heat. Many animals in cold climates have a layer of fat under their skin that keeps them warm, as well as a dense layer of fur or feathers that lies tight against the skin. Some also have a layer of oily, water-repellent hairs.
Animals that live in hot deserts have thick skin or scales that serve as insulation from the heat. Some species of thorny lizard rely on grooves in their thorny armor to cool themselves down and to obtain moisture in their bodies: the grooves channel water across their skin, which then trickles into their mouths. Because of the lack of water in their environment, animals in hot deserts get their water solely from the food they eat, and they must be able to retain that moisture in order to survive. For this reason, their skin does not sweat. Thick skin and scales prevent the water in their bodies from evaporating.
https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/archive-2013-2014/animal-survival-in-extreme-temperatures.html

https://www.scientificamerican.com/article/how-do-arctic-animals-stay-warm/