Answer:
well reptiles are cold blooded and mammals are warm blooded.
Most reptiles develop in eggs and mammals (except monotremes) don't. ☻
Reptiles are covered with scales; mammals are covered in (or at least have some) fur.
Mammals feed their young with milk; reptiles do not.
Reptiles do not have a complete septum to divide the heart into four chambers; mammals' hearts are fully divided into four chambers.
Mammals have more advanced brains and neocortexes; reptiles do not.
In reptiles, the quadrate and articular bones make up the jaw; in mammals, the quadrate and articular bones are in the ear.