subclasses of this should be checked for taxonomic consistency

uberon

hollow bone

UBERON:0008193

Skeletal pneumaticity is the presence of air spaces within bones. Skeletal pneumaticity exists only in synapsids and archosaurs. It is generally produced during development by excavation of bone by pneumatic diverticula (air sacs) from an air-filled space such as the lungs or nasal cavity. Pneumatization is highly variable between individuals, and bones not normally pneumatized can become pneumatized in pathological development. Pneumatization occurs in the skulls of mammals, crocodilians and birds among extant groups, as well as extinct archosaurs including the dinosaurs and pterosaurs. Pneumatic spaces include the paranasal sinuses and some of the mastoid cells[WP]. [Wikipedia:Skeletal_pneumaticity]

• pneumatic cavity of bone