Skeletal pneumaticity

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Skeletal pneumaticity is the presence of air spaces within bones. 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.

The paranasal sinuses in a human, an example of skeletal pneumatization

Cranial pneumaticity[edit]

Pneumatization occurs in the skulls of mammals, crocodilians and birds among extant tetrapods. Pneumatization has been documented in extinct archosaurs including dinosaurs and pterosaurs. Pneumatic spaces include the paranasal sinuses and some of the mastoid cells.

Postcranial pneumaticity[edit]

Postcranial pneumaticity is found largely in certain archosaur groups, namely dinosaurs,[1] pterosaurs, and birds. Vertebral pneumatization is widespread among saurischian dinosaurs, and some theropods have quite widespread pneumatization -- Aerosteon riocoloradensis has pneumatization of the ilium, furcula, and gastralia as well.[2] Many modern birds are extensively pneumatized. The air pockets of the bones are connected to the pulmonary air sacs:[3]

Air sacs Skeleton portion pneumatized by their divercula
cervical air sacs cervical and anterior thoracic vertebrae
abdominal air sacs posterior thoracic vertebrae, synsacrum and hindlimb
interclavicular air sac sternum, sternal ribs, coracoid, clavicle, scapula, and forelimb
anterior and posterior thoracic air sacs - (lack diverticula)

However the extent of pneumaticity depends on species. For example it is slight in diving birds, loons lack pneumatic bones at all.[3][4]

Postcranial pneumatization is rarer outside of Archosauria. Examples include the hyoid in howler monkeys Alouatta, and the dorsal vertebrae in the osteoglossiform fish Pantodon.[5] Slight pneumatization of the centra and rib heads by dorsal diverticula in the lungs of land tortoises has also been documented.[5] In addition, pathological pneumatization has been known to occur in the human atlas vertebra.[6]


  1. ^ Wedel, M.J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates; pp. 201–228 in Wilson, J.A., and Curry-Rogers, K. (eds.), The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley. (link)
  2. ^ Sereno, P.C., Martinez, R.N., Wilson, J.A., Varricchio, D.J., Alcober, O.A., Larsson, H.C.E. 2008. Evidence for avian intrathoracic air sacs in a new predatory dinosaur from Argentina. PLoS ONE 3(9): e3303. doi:10.1371/journal.pone.0003303 link
  3. ^ a b Wedel, Mathew J. (2003). "Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs" (PDF). Paleobiology (The Paleontological Society) 29 (2): 243–255. doi:10.1666/0094-8373(2003)029<0243:vpasat>;2. Retrieved 2014-01-21. 
  4. ^ Schorger, A. W. (September 1947). "The deep diving of the loon and old-squaw and its mechanism" (PDF). The Wilson Bulletin (The Wilson Ornithological Society) 59 (3): 151–159. Retrieved 2014-01-21. 
  5. ^ a b Farmer, C.G. 2006. On the Origin of Avian Air Sacs. Resp. Physiol. Neuro. 154(1–2):89–106.
  6. ^ Bruno Moreira and Peter M. Som. Unexplained Extensive Skull Base and Atlas Pneumatization: Computed Tomographic Findings. Arch Otolaryngol Head Neck Surg, Jul 2010; 136: 731 - 733.