Aphanosauria archosaurs (apart from specialized forms like pterosaurs or theropod dinosaurs). The pelvis (hip) of aphanosaurs shares many similarities with those of early dinosaurs and silesaurids as well as the unrelated poposauroids. Most of these traits can be found in the ischium, a plank-shaped bone which makes up the lower rear branch of the hip. For example, each ischium (on either side of the hip) contacts each other at the hip's midline. This contact is very extensive, although they are not completely fused due to the contact not extending to the upper edge of each bone. In contrast, pterosaurs, lagerpetids, and
Bone A bird's beak is primarily made of bone as projections of the mandibles which are covered in keratin. A deer's antlers are composed of bone which is an unusual example of bone being outside the skin of the animal once the velvet is shed. The extinct predatory fish "Dunkleosteus" had sharp edges of hard exposed bone along its jaws. Many animals possess an exoskeleton that is not made of bone. These include insects and crustaceans. The proportion of cortical bone that is 80% in the human skeleton may be much lower in other animals, especially in marine mammals and marine