Editing Skeleton (section)

=== Fish ===
{{Further|Fish anatomy#Skeleton|Fish bone}}The skeleton, which forms the support structure inside the fish is either made of cartilage as in the [[Chondrichthyes]], or bones as in the [[Osteichthyes]]. The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. They are supported only by the muscles. The main external features of the fish, the [[fish fin|fins]], are composed of either bony or soft spines called rays which, with the exception of the caudal fin (tail fin), have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk.

Cartilaginous fish, such as sharks, rays, skates, and chimeras, have skeletons made entirely of cartilage. The lighter weight of cartilage allows these fish to expend less energy when swimming.<ref name="National Geographic-2021" />