The evolution of limbs played a crucial role in the transition from amphibians to mammals, as it allowed for better terrestrial locomotion and support for body weight, with early amphibians having sprawling limbs, while mammals evolved more adducted limbs. 

The earliest amphibians, evolving from lobe-finned fish, had limbs that were adapted for both aquatic and terrestrial life, with a sprawling posture similar to reptiles. As amphibians spent more time on land, their limbs evolved to support their weight and facilitate movement on land. The synapsid-mammal transition is characterized by a shift from sprawling limb posture to more adducted limbs, which are positioned closer to the body's midline. 

The pectoral girdle, also known as the shoulder girdle, consists of the clavicle (collarbone) and scapula (shoulder blade). It is designed for flexibility and a wide range of motion, allowing the arms to move in many directions while the pelvic girdle connects the lower limbs (legs) to the axial skeleton, supporting the body's weight and transferring it to the lower limbs. 

The pelvic girdle, also known as the hip girdle, consists of two hip bones (also called coxal bones), each formed by the fusion of the ilium, ischium, and pubis, along with the sacrum and coccyx.