Mammals are the only ones that can have fur or hair over their skin. Birds have feathers. Amphibians have moist skin. Reptiles have scaly skin. Fish have scales.
Only mammalian kidneys have a renal pelvis (dilated beginning of the ureter) and renal pyramids (8 to 18 cone-shaped tissues in the renal medulla). The renal medulla (the innermost part of the...
The body covering of mammals is skin, fur or hair. This is one of the defining characteristics of mammals. Note: There is no chemical difference between fur and hair, as both are made up of keratin....