One of the following is a very unique feature of the mammalian body:

Diaphragm is found in mammals only. Homeothermy is found in Amphibians, mammals and birds. Birds and mammals and crocodile have four-chambered hearts. Rib cage is found in most tetrapod. Related Theory Diaphragm, dome-shaped, muscular and membranous structure that separates the thoracic (chest) and abdominal cavities in mammals; it is the principal muscle of respiration. The lungs serve as the gas-exchanging organ for the process of respiration.