The changes seen beginning in the early tetrapods continue in the evolution toward mammals. In the Cat the epaxial trunk muscles are well developed and support the vertebral column and the head, much as they do in Necturus. Most of the Hypaxial musculature is thin and forms antagonistic layers that support the thoracic and abdominal walls and are important in breathing movements. The diaphragm, a structure that is unique to mammals, contains muscles that are derived from this group. The hypobranchial musculature becomes further divided into many units and provides precise control over the tongue.
Appendicular muscles are very numerous and conspicuous.
In the cat these muscles are crucial for body support and locomotion. In the cat the appendages are positioned closer to the axis of the body and provide better support than in amphibians. They suspend the body above the ground, and because of this strong and coordinated muscles are needed. The jaw muscles are much more complex in the cat. Mastication and precise occlusion of the teeth require strong and numerous muscles.