A frog's skeleton is divided into four major sections: the skull, the spine, the forelegs and the legs. While a frog's arms and legs are similar to those of a human, its skull and spine are markedly different.
A frog's forelegs, also called arms, contain humerus, radius and ulna bones similar to those of a human's. However, a frog's radius and ulna are fused together. Frogs' upper legs contain a femur, and its lower leg bones, the tibia and fibula, are fused together.
Frogs typically have four toes on their front legs and five on their back legs, with lengths varying by different species. Tree frogs who do a lot of climbing and aquatic frogs who require webbed toes for efficient swimming tend to have very long digits. Frogs that live in the mud typically have shorter toes that they utilize as shovels.
The skull of a frog contains five bones and it is connected directly to the spine without a neck vertebrae. At the terminus of the spine, a frog's vertebrae are fused together into a single bone. Due to the lack of ribs, a frog's pelvis is able to slide up and down its spine. This skeletal adaptation is thought to increase jumping ability.