Editing Cetacea (section)

=== Skeleton ===
{{unreferenced section|date=April 2018}}
[[File:Whales skeletal system comparison.png|370px|thumb|Diagram featuring the typical skeletal of a toothed whale (top) and a baleen whale (bottom)]]
The cetacean skeleton is largely made up of [[cortical bone]], which stabilizes the animal in the water. For this reason, the usual terrestrial compact bones, which are finely woven [[cancellous bone]], are replaced with lighter and more elastic material. In many places, bone elements are replaced by cartilage and even fat, thereby improving their [[hydrostatic]] qualities. The ear and the muzzle contain a bone shape that is exclusive to cetaceans with a high density, resembling [[porcelain]]. This conducts sound better than other bones, thus aiding [[biosonar]].

The number of [[vertebrae]] that make up the spine varies by species, ranging from forty to ninety-three. The [[cervical spine]], found in all mammals, consists of seven vertebrae which, however, are reduced or fused. This fusion provides stability during swimming at the expense of mobility. The fins are carried by the [[thoracic vertebrae]], ranging from nine to seventeen individual vertebrae. The [[sternum]] is cartilaginous. The last two to three pairs of ribs are not connected and hang freely in the body wall. The stable lumbar and tail include the other vertebrae. Below the [[caudal vertebrae]] is the [[chevron (anatomy)|chevron bone]].

The front limbs are paddle-shaped with shortened arms and elongated finger bones, to support movement. They are connected by cartilage. The second and third fingers display a proliferation of the finger members, a so-called hyperphalangy. The shoulder joint is the only functional joint in all cetaceans except for the [[Amazon river dolphin]]. The [[collarbone]] is completely absent.