Final answer:
The elements of limbs that are conserved across vertebrates include the placement of limbs underneath the body, the rotation of the femur and humerus to point forward, and the decreased size of adductor muscles.
Step-by-step explanation:
The elements of limbs that are conserved across vertebrates include the placement of limbs underneath the body, the rotation of the femur and humerus to point forward, and the decreased size of adductor muscles. These adaptations allow for more efficient movement over land. Additionally, vertebrates have a closed circulatory system with a heart and a system of muscles attached to the endoskeleton for movement.