Skeletal pneumaticity
Encyclopedia
Skeletal pneumaticity is the presence of air spaces within bones. Skeletal pneumaticity exists only in synapsid
s and archosaur
s. 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.
s, crocodilians and bird
s among extant groups, as well as extinct archosaur
s including the dinosaur
s and pterosaur
s. Pneumatic spaces include the paranasal sinuses and some of the mastoid cells
.
s, 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.
However, there are unusual instances of postcranial pneumaticity outside Archosauria; the hyoid in the howler monkey Alouatta is pneumatized, and the osteoglossiform fish Pantodon pneumatizes some vertebrae from its swim bladder. In addition, pathological pneumatization has been known to occur in the human atlas vertebra.
Synapsid
Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...
s and archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
s. 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.
Cranial pneumaticity
Pneumatization occurs in the skulls of mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, crocodilians and bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s among extant groups, as well as extinct archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
s including the dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s and pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
s. Pneumatic spaces include the paranasal sinuses and some of the mastoid cells
Mastoid cells
A section of the mastoid process of the temporal bone of the cranium shows it to be hollowed out into a number of spaces, the mastoid cells, which exhibit the greatest possible variety as to their size and number....
.
Postcranial pneumaticity
Postcranial pneumaticity is usually found only among certain archosaurs—dinosaurs , pterosaurPterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
s, and birds. Vertebral pneumatization is widespread among saurischian dinosaurs, and some theropods have quite widespread pneumatization -- Aerosteon riocoloradensis has pneumatization of the ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
, furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....
, and gastralia as well.
However, there are unusual instances of postcranial pneumaticity outside Archosauria; the hyoid in the howler monkey Alouatta is pneumatized, and the osteoglossiform fish Pantodon pneumatizes some vertebrae from its swim bladder. In addition, pathological pneumatization has been known to occur in the human atlas vertebra.