Substitution Bone

or cartilage bone, bony parts of the skeleton of vertebrate animals resulting from the ossification of the cartilaginous skeleton. Substitution bone is formed from coarsely fibrous or lamellated bony tissue. It usually has a cavity of bone marrow and is covered with periosteum. Substitution bone first appeared in fish in the course of evolution, but only in higher vertebrates did bone completely replace cartilage. Examples of substitution bone are the humerus and the femur.