There are some characteristics that are unique to mammals: hair, sweat glands, mammary glands, and the neocortex in the brain; reptiles lack all of those features and have scales in place of hair....
Mammals Reptiles 1) Mammals have fur. 1) Reptiles have scaly skin. 2) Mammals produce milk. 2) Reptiles (most of them) produce poison. 3) Mammals have four 3) Reptiles have three chambered heart....
A mammal has a four chambered heart whereas a reptile has a three chambered heart.A mammal has 2 atriums and 2 ventricles when reptiles have 2 atriums, but only has one ventricle.
The main noticeable difference is their skin. Reptiles have thousands of overlapping scales loosely connected to each other. Amphibians have a breathable one-piece skin.