A major problem reptiles encountered when they left water was the adjustment of their internal temperature, as the temperature fluctuations on land are much larger. Nature showed great ingenuity with species such as edaphosaurus (290 million years ago) who had a leather tissue as a solar collector, supported by a series of vertical bones on his body. It belonged to the group of chordate who dominated on earth for 40 million years before disappearing.
Other species learned to increase their temperature internally by burning food faster, which required more food. In trying to find it, they started to walk rather than crawl and acquired whiskers to enhance smell. In order to have better digestion, their teeth varied in cutters and bankers so they could chew instead of swallowing the whole food. For all of these characteristics that represent the transition from reptiles to mammals, they were called Mammaliaformes.
They were disappeared about 250 million years ago. In their place a new species evolved, more advanced, Cynodontia (250-230 million years ago) the ancestors of mammals. Cynodontia had developed homothermia, the ability to maintain constant internal temperature independently -to a degree- from ambient temperature changes. That resulted in high biochemical performance and functions.
Cynodontia, such as Prokimosuchus, had shorter tails, elbows that bend back, knees bending forward, stronger jaws and differentiated teeth. They developed a diaphragm for breathing and a bone palate that allowed breathing along with chewing. The hair spread throughout the body, the number of bones decreased at the jaw, some new bones evolved into the ear, giving better hearing; therefore better awareness of the environment, improved wit and agility, an advantage in the struggle of survival and evolution.
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