Cartilage
Are you talking about shark skeletons? Yes, they are bones. However, they are made of a different, softer material, than most bones from other animals - cartilage.
Marrow. It makes blood cells.
MANTLE
Infants.
The most structural joint that occurs in the human skeleton is hyoid bone
The appendicular skeleton has more bones than the axial skeleton. The axial skeleton includes the skull, spine, and rib cage, which have a total of 80 bones. In contrast, the appendicular skeleton includes the bones of the limbs, shoulders, and hips, totaling 126 bones.
Skeletons do not move on their own. Movement is achieved through the muscles that are attached to the skeleton and controlled by signals from the nervous system, which coordinate and stimulate muscle contractions. Bones provide the structure and support for movement, but they do not have the ability to move on their own.
A shark has the most flexible skeleton among the three. Sharks have cartilaginous skeletons that provide greater flexibility compared to the bony skeletons of frogs and lionfish. This flexible skeleton allows sharks to move more dynamically in the water.
The Chickadee like most Birds has a hollow skeleton which enables them to fly.
cartilage
On their backs!
infants