Final answer:
As animals moved from water to land, the skeletal system changed by repositioning limbs under the body, which led to a more efficient stride due to decreased adductor muscle size and increased scapula mobility.
Step-by-step explanation:
Much of our understanding of tetrapod muscle function is derived from studies of the appendicular skeleton differences between land and aquatic animals. As animals transitioned from water to land, the skeletal system evolved significantly.
One major change was the relocation of the limbs from a sprawled position to being placed under the body, which increased efficiency in terrestrial movement. This structural change led to decreased adductor muscle size and an increased range of motion of the scapulae.
Additionally, the rotation of the femur and humerus meant that the ends of the limbs and digits were pointed forward, aiding in forward motion. Thus, the answer to the question on how the animal skeletal system evolved as animals moved from water to land includes these adaptations, rather than decreased ossification of bones.